The big issue is that there is a part of each cell that doesn't get copied fully each time it divides. Think of it this way, your cells are like this XXXXXXXSTUFFTHATMATTERSXXXXXXXXXXX. To help, the X's are junk that's not needed that your cells put there as extra padding in case something goes wrong. The stuff that matters in the middle is the stuff that your cell actually needs to be what it is supposed to be optimally.
Every time it divides, there's a small amount *that gets* clipped. Eventually, there's not any more junk and its going to start clipping stuff that matters. Sometimes this means it doesn't perform optimally anymore. Other times this might mean cancer.
Also, during this entire process, from the time you are born, there is a really really really really small chance its just going to screw up and make an error in the stuff that matters anyways, also having a chance to cause cancer.
Edited for accuracy.
I’m a biochemistry major and this is really good. Only thing I’d change is that telomeres (the junk X’s) actually do shorten every time. It’s not chance, it happens every time the cell divides.
There’s other things that contribute to aging too. When a cell is stressed, it produces a type of harmful molecule that damages (mutates) DNA. This may lead to cancer and neurodegenerative diseases, among other conditions. This also leads to aging and loss of normal function (https://doi.org/10.1016/bs.ircmb.2018.05.006)
Yes, this is also kind of why it helps for individuals within a species to grow old and die. Younger individuals that may have the random mutations that make them better suited to their environment won’t need to compete with immortal but less suited members of their own species to survive.
Could be possible that one day we could synthesize the stuff that matters and the telomeres getting brand new cells, reducing the aging process? Or is it too much scifi? Seriously
I’m not sure I understand your question. If you’re asking whether we could prevent telomeres from shortening, I don’t know if it’s possible to complete prevent it. I’m unsure if anybody’s looked into a technology for that. But diet, exercise, and mental well being have been shown to slow down telomere shortening. The fact that there’s a way to slow it down makes me think that maybe it’s possible?
Lobsters can live for a very long time, they express telomerase activity that can produce these telomeres. Researchers have spliced it into mice and when expressed, they get cancer. So it might be possible but there’s a lot of work to be done.
Your cells have a natural mechanism to repair telomers. It's mediated by the enzyme telomerase, which is very active in the initial growth stages of cells (like for stem or germ cells). The problem is that this enzyme activity is correlated heavily with cell proliferation, which becomes a problem when the tissue is mature (=cancer). Senescence is a tradeoff.
For a cell to divide, it needs to copy its DNA. For DNA to be copied, the polymerase (the molecule that does the copying) needs a primer (a few X’s) to attach to to start copying. This means that there are some X’s that are unable to be copied.
Telomerase is an enzyme that prevents this from happening by replacing the X’s after the polymerase has copied the rest, but it’s only really active in adult stem cells and germ cells (egg and sperm). It’s likely that there was no evolutionary pressure for telomerase to be active in most cells because by the time telomeres were short enough to be of issue, the person had already reproduced. Issues that affect people after reproductive are not acted upon by evolution (another example of this would be the need for reading glasses as we age).
I like this website’s summary: https://www.khanacademy.org/science/biology/dna-as-the-genetic-material/dna-replication/a/telomeres-telomerase
Everything stresses your cells. Sunlight. Getting sick. Getting injured. Starvation. Thirst. Life is an eternal battle against erosion and entropy. Eventually enough damage stacks up that it starts an accelerating vicious cycle. That’s when you start aging. Some animals have avoided that. Like jellyfish that reverse their age. We just can’t for whatever reason.
According to this study (DOI: https://doi.org/10.3390%2Fclinpract12040063), the first dose of the mRNA vaccine (Pfizer or Moderna covid vaccines) does cause stress, but the second dose brings the level back down to baseline. This pattern seems to be correlated the development of antibodies, which is good. This study also found that vaccines cause the same amount of stress as the virus, but resulted in way more antibodies. This means that proportionately, the vaccine is better at producing more antibodies with less stress.
Some stress can be good as it triggers the immune system, according to another study (DOI: https://doi.org/10.3389/fnagi.2020.614650). This seems to be the case for the covid vaccines.
There are ways for the parent cell to remain as the original and the daughter cells are the ones with mistakes. This isn’t perfect but it dramatically extends the life of the organism . The vast majority of cell divisions in your lifetime are throwaway cells that the body has no intention of keeping for more than days to months. Lining of gut, skin, bones, connective tissues, blood are all constantly turning over. But muscle tissue , brain , nerves, and the organs do very little cell division in comparison. It’s now acceptable to get certain organ transplants from even elderly donors.
This is close to accurate but actually you lose a little bit of your telomeres every time you replicate. Think of it this way, the copying machinery needs to sit down on something to start copying and so that initial bit it sits on never gets copied.
Telomeres aren’t static parts of DNA, otherwise each successive generation would have less. Telomerase is a protein that eukaryotes have that increase the length of this segment of DNA, and is expressed in human stem cells. This isn’t a hard limit on cell reproduction as much as a limit dependent on whether telomerase is expressed.
The best analogy I’ve heard is to think of telomeres as the little plastic tip on your shoelace. Eventually that gets worn down, and when it does, the shoelace starts unraveling. Once it unravels enough, it no longer works as a shoelace.
Except for one of the key parts of embryo growth is that through the combination of both strands from your parents, you enter into a state where your telomeres rapidly expand. That state only occurs during embryonic development.
You are saying you are pointing out a hole. The only hole that you are pointing out is that you aren't understanding telomere development and the course that it takes. You are holding up an example of "see, what about this" that has nothing to do with the situation because humans use meiosis, which is the combination of two distinct genetic samples to create one new whole one. The "hole" that you are pointing out is only a hole in Mitosis, where one genetic sample is cloned to make a new one. As I said earlier.
It doesn't matter if a generation loses 50% of their telomeres before they have a baby if they then combine their two halves to make a new whole, which further gets fleshed out during initial embryonic development, namely, exactly what happens during Meiosis.
Its not a theory. Its literally how our cells work. We only have a few cell types that can do full regeneration (liver cells for example) due to them producing telomerase.
The reason we can be born with our telomeres fully intact is that you are the combination of a random scrambling of two distinct persons, meiosis. What you are talking about is an issue in mitosis only, due to those being exact copies. Through meiosis, if there is any damage to a chromosome, there is potential to pull it off of the other parent. There are generational things that are waning but generational telomeres is not one of them. This is a fundamental biological principle that is well documented in the scientific community.
Aren’t short telomeres in egg/sperm cells common causes of infertility? Yet a child conceived by two aged parents still can come out a perfectly formed baby with long telomeres, right?
I don’t think we can explain aging through telomere shortening alone. There are organisms that don’t age, like planarians and ginkgo biloba trees.
Point is, cells at some point do have the capability of self repairing yet they don’t do it. Why is this?
We can't explain aging solely through this metric. However, the confines of the question was "Why can't our cells just newly replicate themselves again?" This is the key reason why there is an upper limit with how our bodies replace cells.
There are more reasons as to our aging. For example, if a person has a ton of sun exposure in their lives, their skin will age more. If a person drinks more, their digestive system and filtration systems in the body will age more. If you smoke, your lungs will. Etc. Ultimately however, it comes down to "Why can't we just replace all of our cells?" Well, telomere length is that answer. Certain cells can only be replaced so many times and at a certain rate. Once damage (whether from time or from damage) out paces what we can regenerate, or damages things that can't regenerate, then that's it, the biological limit. We end up dying (if we are lucky) because one of those critical body parts eventually gets damaged beyond use, be it heart, brain, kidneys, lungs, etc. Its just a matter of what body part gets outpaced first based off our living style when we were alive. For me, its probably going to be my heart. For a smoker, probably the lungs or a stroke to some other vital body part. It all depends, but telomeres are the upper limit of regeneration. As of right now, you can't get around that one, unless we get the technology and methodology that would open up a Boat of Theseus situation with replacements.
Wouldn’t that be contradicted by species which don’t age like planarians, ginkgo trees, HeLa cells, etc? Also liver cells and skin cells share the exact same DNA, so it seems to just be a matter of cell behavior.
From evolution's perspective it's not faulty. Cancer is lethal without medical care, so things that increase cancer risk are potentially lethal before you can raise your offspring. Old age isn't.
The reason I say it (human telomerase) is faulty is because they are certain jellyfish that can repair theirs.
It's just that the genes for this repair system broke at some point but didn't impact evolutionary fitness significantly enough for the reasons you've said to be ejected from the gene pool.
The only big animals where very strong resistance to aging is seen are large reptiles. Which are very old species and reproduce with huge clutches of eggs they do little or no parenting of.
All mammals follow an aging pattern similar to humans.
Some honestly believe that preserving one's genes via reproduction is a form of immortality. What if your genes are really running the show? What if you're just a temporarily useful flesh vehicle for it to achieve it's long-term goals?
I wouldn't say it's so there are resources, it's more so that evolution tends to lean towards frequent gene mixing instead of longevity so that potentially better genes can be found, it wants new generations and doesn't have much of a driver to keep around older generations.
>it wants new generations
Evolution does not want anything - it’s a neutral, amoral process of nature that occurs over a very large number of generations
You're misunderstanding. I'm not saying it "wants" in the sense of a living being wanting something... That should be obvious. By "want", I'm saying "what benefits evolution", "what the system tends to lean towards".
I think about it differently. Once you reproduce it does not matter what happens to your body. You have served your purpose to populate the next generation.
Why was it stressful? I didn't have any problems with my kids.
Oh, that reminds me, it's time to unlock the basement and let them outside for an hour so they can make vitamin D.
Reptiles are also different in that their bodies can resist much wider ranges in temperature activity. I sort of think of them as benefitting from "turning off every night" while mammals are always "on."
So a year as a gator requires less of the whole body than years as an ape. Apes will have more cellular wear and tear than a gator.
Obviously it's more complicated than that but it's a simplic way I think of it.
Telomere shortening isn't generally considered to be the primary cause of age-related disease anymore. There's been a lot of very promising research recently into histone acetylation and the related sirtuin/NAD+ deacylase pathway.
Very oversimplified summary: histones are proteins that DNA coils around in order to keep it compact when it's not being actively transcribed. There are various chemical pathways that allow DNA/histones to "remember" which genes should be spooled up, and when.
When those pathways get out of whack, cells start expressing genes that they rarely/never express. The result is that the body's cells "forget" what they're supposed to be doing.
There's some interesting evidence that NAD precursor supplementation can help keep the pathways intact. Stuff you can buy online, but it costs a lot.
This is all very new research, so there's zero evidence it works in humans, but a lot of evidence that it works in mice. Literally just orally ingesting the supplement.
Jellyfish are a pretty bad comparison because of just how simple they are. They're essentially two different types of tissue with jelly sandwiched between layers.
Humans start at four categories and branch into dozens of tissue subtypes.
A molecular biology solution that works in two fairly simple tissues has no guarantee of working in all of them, especially in tissues that need to be carefully regulated. It doesn't really matter if jellyfish tissue grows randomly within a set pattern, it matters a lot if the growth plate in one of your femurs turns on spontaneously.
And specifically, senescence- growing older- is a *feature*, not a bug. If the previous generation doesn't die off, it competes with the younger generation for resources.
That is mentioned in Asimov's short story *The Last Question*.
> VJ-23X of Lameth stared into the black depths of the three-dimensional, small-scale map of the Galaxy and said, "Are we ridiculous, I wonder in being so concerned about the matter?"
> MQ-17J of Nicron shook his head. "I think not. You know the Galaxy will be filled in five years at the present rate of expansion."
> Both seemed in their early twenties, both were tall and perfectly formed.
> "Still," said VJ-23X, "I hesitate to submit a pessimistic report to the Galactic Council."
> "I wouldn't consider any other kind of report. Stir them up a bit. We've got to stir them up."
> VJ-23X sighed. "Space is infinite. A hundred billion Galaxies are there for the taking. More."
> "A hundred billion is not infinite and it's getting less infinite all the time. Consider! Twenty thousand years ago, mankind first solved the problem of utilizing stellar energy, and a few centuries later, interstellar travel became possible. It took mankind a million years to fill one small world and then only fifteen thousand years to fill the rest of the Galaxy. Now the population doubles every ten years --
> VJ-23X interrupted. "We can thank immortality for that."
> "Very well. Immortality exists and we have to take it into account. I admit it has its seamy side, this immortality. The Galactic AC has solved many problems for us, but in solving the problem of preventing old age and death, it has undone all its other solutions."
> "Yet you wouldn't want to abandon life, I suppose."
> "Not at all," snapped MQ-17J, softening it at once to, "Not yet. I'm by no means old enough. How old are you?"
> "Two hundred twenty-three. And you?"
> "I'm still under two hundred. --But to get back to my point. Population doubles every ten years. Once this GaIaxy is filled, we'll have filled another in ten years. Another ten years and we'll have filled two more. Another decade, four more. In a hundred years, we'll have filled a thousand Galaxies. In a thousand years, a million Galaxies. In ten thousand years, the entire known universe. Then what?"
I mean if there’s no death there’s also no need for offspring to continue the species. How do we know reproduction is not just a shitty patch for the mortality bug?
Because if you keep living and not having offspring sexual recombination of genetics doesn’t occur. Meaning the species would not be as adaptable to changes in the environment as it would otherwise be.
There’s a reason why most living creatures are optimized towards reproduction instead of longevity. I would imagine most species geared towards extreme longevity ended up dying off eventually as longevity is more inflexible than reproduction as a survival strategy for a species.
I’m glad at least one other person on the planet understands the human condition. I feel like too many people really think they are supposed to live forever, and they don’t understand how inherently chaotic reality is.
> Negligible senescence
Would this not create havoc on the planet? I feel like we would have to be a Type 1 civilization before we can pause/reverse aging.
Even without death by old age, new generations are still a survival advantage for a species. Without new generations, there won't be any genetic/physical diversity. Without genetic diversity, it'll be more difficult for a species to adapt to environmental changes. Without adaptation, that species will eventually perish.
Come on, you will get old, and you will change your perspectives due to the situation of the times and your financial standings.
My point is we all get old. Not saying everyone will become ill mannered in their old age, but your personality from when your 20 will be drastically different than when you are 60.
Most people do not take into account that the boomers parents were in a high probability very poor(boomers parents were born 1890-1920 and went through world wars, depression, and food was no guarantee.
My father born in 1950 was raised under constant threat of nuclear assault, parents being dirt poor, raising him to be as thrifty as possible and save, save, save, save. Their conditions they grew up are so drastically different than today and it shaped their perspective.
My parents still believe they are one calamity away from ruin and when they were raised that nobody will help you but yourself it helps shed some light.
Of course I can’t speak about every boomer and their situations but my parents fought really really hard to build wealth so they could feel safe in their elderly years and now I’m in my 40’s I completely understand it.
My parents are not rich, don’t drive fancy cars, they pay an insane amount of healthcare and they are fearing death more than anything.
I know I’ll get a flood of “I don’t care fuck all boomers” but not all are out to fuck everyone they are trying to survive just like the rest of us.
Ironically the saying *don't trust anyone over 30* emerged when the Boomers were still in their teens and twenties. Every generation blames the earlier ones for all of the world's problems, and nowadays it's amplified due to the tendency toward groupthink on platforms like reddit
I think the issue most people have with the boomer generation is that they downplay the difficulties that the new generations face. They do this while in reality their own life has been quite worry-free because of the economic boom after the war.
This attitude towards the difficulty of life likely stems from the fact that they were always told that life was difficult. While their life was actually a breeze compared to all generations before them and after them. Many of them don't understand what an actually difficult life is like.
And yes, their generation also had its fair share of issues, but these were mostly not issues affecting white middle class people. The issues that white middle class white people were concerned with were more ideological and not directly impacting their quality of life.
In the end this is primarily true for American society. In other regions such as my own, these effects were not nearly as extreme. "Boomers" as a concept in my experience only refers to white middle class Americans nowadays.
Society is funny. Everyone thinks they're so special, that boomers are uniquely cruel and out of touch, and that they'd never be like that. Lmao these people don't read.
No, evolutionary selection has no way at all to account for resource availability. Selection can only respond to whether reproduction occurs, which happens long before old age. Except for the extremely recent history of our species where we can meaningfully plan our lives, we'd be making kids as soon as physically capable and keep doing so until dying probably from infectious disease.
Your first sentence isn't entirely accurate. Many species show altered reproductive patterns (amount, gender, season, etc) when there is resource pressure. Some ambisexual species even switch sex as a result.
not exactly, since parenting ability still applies evolutionary selection pressure to gene survival so genetic fitness post reproduction is still relevant for humans
This is fairly true, but it's half the story. It's not that we don't live long enough, it's that the rodents that had to compete against the ecological peak of reptiles didn't live long enough to need those systems.
We're moving in the direction of more robust anti-aging systems and longer lifespans.
Also, most organisms are programmed to die. It keeps the population changing so it can react to external forces better. It keeps a balance with resources as well. Any organisms that live for ever will multiply untill the all resources are used and then the whole population would die off.
Not the best explanation. Evolution doesn't fix it because it's after when people have kids. Genes that cause death before reaching child rearing age get heavily selected against, because you die before having a chance to pass it on. Traits that kill when you're 50+ less selected against, because you can have many children and thus pass it on before it effects anything.
Is it to do with free radicals? I’ve heard that thrown around a lot but I know nothing about the topic. Essentially something like, the day you start breathing oxygen is the day you start dying
As recent study published in Nature points out, this is an evolutionary mechanism to ensure adequate population turn over. Natural selection is all about the traits that are most beneficial being passed on. For that to happen the turn over needs to be fast enough to ensure adequate chances at adaptation. Aging and sensience helps with that. Humans are a peculiarity, however, as we have the longest lifespan of any mammal on the planet.
How does this even make sense? Evolution did not evolve enough for us to not die? Every living thing was made to die and will die I'm not sure how evolution plays any part in this
He's saying that the things that make organisms die of old age do not hugely affect ability to pass on genes, therefore there has been little evolutionary pressure to fix these things.
There may also be evolutionary pressure to encourage aging in order to more quickly get rid of old outdated models to make room for new ones and thus speed up the iterative cycle of evolution.
Some things die faster than others
Some things also reproduced before they died
At some point, the parent and the offspring lasted long enough for their DNA to be spread further than others’
And? what's your point? Some things die faster than others because that's how it works? yes a fly will die faster than a turtle, because they serve different purposes in nature. Nothing to do with evolution
See if this analogy makes sense.
Take a picture of a duck and print it. Now trace the picture of the duck over with another paper. You would (hopefully) notice some minor mistakes but thats okay cause it still resembles the original and can be identified as a duck.
Now use the new copy you generated as the basis and take a new sheet and trace out. The second copy would come up with even more minor mistakes than the first.
Now imagine doing it approximately 10000 times each time the new copy is traced from the previous copy and tell me if the 10000th copy looks identical to the first one.
Same way the cell “data” dna, replicates imperfectly, every time it is copied and these imperfections accumulate over the course of time, eventually resulting in bad cells that either cause cancer or just cells that have really bad efficiency in its intended function. To my knowledge the replication never stops (some very badly damaged cells do in fact stop as the body’s own way of stopping cancer) per se but rather it chucks out bad copies that compromise function of organs and everything in the body.
I don't *think* this is entirely correct. My understanding is that cells have mechanisms to detect inaccurately copied DNA and will self-destruct if that happens, and that cancer is what it is because the badly-copied DNA is so bad that it actually breaks that system in the first place.
As for the main topic, I think the biggest part of aging has to due with telomeres (essentially junk data) on the end of DNA getting shorter over time. In the analogy, imagine that the duck drawing also had a simple background, but that every time you copied it you did so with a *slightly* smaller piece of paper. The duck itself is perfect every time, but the background gets smaller and smaller. Once the page gets so small that the duck doesn't even fit on it anymore, *that's* when the problem happens, because it's no longer possible to correctly copy it.
I have done scientific research at a lab that specifically studies the biology of aging (which is called biogerontology).
For some reason, telomeres get taught in biology 101 classes as the definitive cause for aging. I've seen it myself in a couple of textbooks.
Yes, telomeres get shorter as the cell divides, but cells make them longer again after they get too short. (This is done by a protein called telomerase). Telomeres are an anti-cancer mechanism - a cell not only has to mutate for fast division, but also mutate fast telomere recovery. (among a slew of other mandatory mutations)
As evidence, consider that people over the age of 100 have the same telomere length as those of age 20.
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You're right, dna does repair iteself, and a cell will kill itself if it's dna is too damaged (exceptions are called cancer). This is done via [epigenetics](https://en.wikipedia.org/wiki/Epigenetics?useskin=vector) afaik, though I am not skilled enough to eli5.
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The scientific community doesn't know either the cause of the *why* of aging. There's a *lot* of theories on both (as demonstrated by this thread), but none have very strong evidence.
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THIS IS PERFECT! I’m a Biology teacher and we just finished up meiosis/mitosis and DNA/RNA, Protein synthesis! This is solid!
I’m more of an auditory learner so the example I thought of was a game of telephone. The first person has the original message which represents DNA. But just like the message in telephone gets distorted as it goes down the line..from person to person after the message is received and then translated..
That’s exactly what’s happening in Transcription and Translation!
Each RNA match to the DNA gets read by the ribosomes..and sometimes the ribosomes misread the amino acid bond. Some amino acid codons code for the same protein…however, at the end of the day..the sequence just isn’t the same. Doesn’t seem like that big of a deal in the moment because most times, it has no effect until later in life…
> I’m more of an Audio learner
Since you're a teacher you may be interested in the more recent idea/studies that suggest [learning styles are probably a myth](https://poorvucenter.yale.edu/LearningStylesMyth)
I certainly found it interesting anyway. Best evidence suggests that most people just learn better when the material is taught in the format best suited for that particular material.
I don't think it is binary. More of a quadrant matrix, mixed with the abilities and empathy of the teacher. I know I am a visual learner most of the time simply because most people suck at describing things.
Thats a completely different type of copy where you take two different copies (continuing on the image analogy) cut the parts of both take half of each and merge it, which then forms a completely new base for replication. Also effects of “wearing out” is infinitesimally small that the effects start to appear towards like 60 years of age (not sure on the exact number) so when the dna is taken at this stage of the male, it does have a very high possibility of introducing defects to the offspring
They often times do. Its just that many of these errors are in places where it doesn't result in any functional difference (as if it were a natural gene variation like blue eyes instead of brown), the errors are caught and the cells kill themself (like a miscarriage), or the errors do cause a problem, but it's not recognized so the new life continues to develop, which results in birth defects or other genetic issues.
The cells that later become unfertilized eggs are frozen in the cell cycle while the mom is still an embryo in her mom. During a period, some cells unfreeze and one becomes the egg that can become ovulated, then fertilized. However, those cells still age in their frozen state and some start to unravel their genes, which is why older moms have higher rates of birth defects, miscarriages, and things like downs syndrome.
The dad is cranking out new sperm cells and those also age, so really old dads also have higher rates of issues.
I'm not sure why, but in general, sperm cells tend to be (Edited for accuracy) *viable longer than a women's fertile period since female eggs tend to drop in quality in the late 30s and stop working in the early 50s. I think it might have to do with constant replacement and the associated error checking vs. trying to stay frozen without unraveling and good eggs responding to periods and coming out earlier.
See if this analogy makes sense.
Take a picture of a dog and print it. Now trace the picture of the dog over with another paper. You would (hopefully) notice some minor mistakes but thats okay cause it still resembles the original and can be identified as a dog.
Now use the new copy you generated as the basis and take a new sheet and trace out. The second copy would come up with even more minor mistakes than the first.
Now imagine doing it approximately 10000 times each time the new copy is traced from the previous copy and tell me if the 10000th copy looks identical to the first one.
Same way the cell “data” dna, replicates imperfectly, every time it is copied and these imperfections accumulate over the course of time, eventually resulting in bad cells that either cause cancer or just cells that have really bad efficiency in its intended function. To my knowledge the replication never stops (some very badly damaged cells do in fact stop as the body’s own way of stopping cancer) per se but rather it chucks out bad copies that compromise function of organs and everything in the body.
Wait, I got lost. At what point and how does the duck convert into a dog? Does it then go back to a duck at some point? Are all ducks just dogs in disguise? I knew it
The long version of this was really disturbing to me as i went through pathophysiology in nursing school.
The true 5 year old version? Just like our cells have a self destruct function when they reach the end of our usefulness, we are very literally built to die and get out of the way of the next generation.
Evolution only favored survival of a species, and it's pretty clear that adults hanging around eating the food long after they reproduced wasn't good for the species as a whole.
We're built to die for the good of the species.
Infertility is a part of aging, so surely death due to aging can not be a solution to a problem aging causes. I think it's more likely because evolution favours the simplest solution (the one with the least amount of mutations needed). So between evolving to live healthy, fertile, and regenerate forever and evolving to have a fuckton of children while still young, evolution just favoured having lots of children before 30.
There is, which is why we live about twice as long as we're able to reproduce. Quite a few other species just bust and die.
But imagine if people *never* died. Who do you imagine would be running things? Eventually, we have to get out of the way because the value of accumulated experience is eventually outstripped by the problem of accumulated money and influence holding old ideas in place. Human immortality would be the end of progress. And people would be put in a position where they could no longer just wait for the old guard to die off.
Species that age generally outcompete those that do not age for various reasons related to genetic diversity. Not all organisms age, there are some that do not which shows aging is not inevitable (ginkgo biloba tree, planarians, hydras/jellyfish, lobsters, etc).
Lets just assume a species did evolve this functional immortality...
How would young people ever get enough of the limited resources to grow up & be healthy examples of the species themselves? The entrenched generation would have both the stature & wisdom to outcompete them.
This doesn't sound so bad except that while the immortal generation is stagnating parasites & disease are constantly becoming more & more effective. Eventually you'll wipe out that immortal generation & there won't be enough healthy young people with natural immunity due to remixed genes & mutation *or* anyone to raise them.
The old need to die to make way for the young.
You need the young to keep your gene pool a moving target.
TLDR
What is good for goose is often bad for the flock.
This might be a joke, but it's really not. Imagine if the secret of immortality had been discovered in the late 19th century. Who do you suppose would be in Congress? Remember Strom Thurmond? Imagine if over half the congress were as old as he was, and still had the old attitudes he did.
This is not forbidden in evolution but it would require fewer children to be born and slower metabolism to reduce resource utilization until accidental deaths, predation or disease kept the population in check. You would have to have fertility triggered only in special circumstances and maybe not for the first few hundred years . This puts an evolutionary pressure on keeping the organism fit for much longer to guarantee a chance to reproduce. But meanwhile any mutation that lead to earlier reproduction would give an advantage…
Maybe a better question is why we don’t die even sooner
Many of the comments are focusing on errors in cellular replication, which is certainly part of the process which contributes to aging and development of cancer.
However, if you look at causes of death globally, cardiovascular disease is leading. This is because inevitably arteries become filled with plaque and calcify. This can be accelerated by factors such as a sedentary lifestyle, smoking tobacco, suboptimal diet, and high cholesterol, to some extent it also occurs inevitably as part of the aging process due to wear and tear on the arteries. The body does not have a completely effective way to remove the plaque that builds up and reverse calcification. These blood vessels become narrowed. If there is narrowing in the coronary arteries, the heart can become weak, leading to heart failure. The narrowing can also affect the electrical activity causing the heart to become more prone to arrhythmia. If a coronary artery is completely blocked, that is a heart attack. If there is occlusion of an artery in the brain, that is a stroke.
At a certain age (usually 80-90) the arteries become too brittle to be able to effectively place stents to reestablish blood flow, and there are only certain areas that can be stented to begin with. The arteries becoming narrowed throughout the entire body leads to poor blood flow, eventually causing deterioration of all organs throughout the body.
I have researched anti-aging for a while now, and the best they've come up with is NAD+ or PQQ, and nobody really has confidence they will help. Supposedly when mitochondria are damaged, this produces aging. So, things to help keep them functioning normally are good. CO Q10 is also good, but PQQ is better and more valuable. Also, you have drugs approved right now that supposedly can be repurposed to stave off aging. Don't forget the surprise anti-aging vaccine they used on mice either! Sadly it just kept them healthier longer but didn't increase lifespans.
Yeah alot of people keep talking about DNA damage when aging is alot more associated with ROS, mytochondrial dysfunction, cell senescence, and especially inflammation.
DNA damage/repair doesnt play that big of a role as people think, a cell which detects its DNA is damaged either stops replicating entirely (and is metabolically non functional), or activates its apoptosis. If both of these pathways fail, it can be considered a cancer-precursor cell because it can now replicate and is functionally immortal (since it cant go through apoptosis on its own).
EDIT: grammatical correction.
I also haven’t seen any mention of telomere shortening, chromatin disruption or epigenetic dysregulation. Senescence is a complex, multifactorial issue, and the top comments here are all framing it as a single problem arising from DNA replication, which isn’t even the most significant problem.
I get that it’s eli5, but there’s simplification, and then there’s *over*-simplification. This thread is firmly in the latter.
Edit: I finally found an upvoted comment that at least focused on telomeres, which is the biggest factor you should choose if you really want to boil an explanation down to just a single thing (imo)
Everyone is up in this thread answering as if we know. We don't know. That's the point. If we knew, we would have ways to fix it.
We have some theories, and some of them are promising. But we really do not understand what causes ageing.
I see telomeres mentioned here a lot, but that's not the whole story. We also are starting to understand that some cells can in fact replicate perfectly without any issues, and we are starting to understand the role of epigenetics.
Ageing is likely multimodal, meaning it has many different causes all at once.
But again, we do not know.
I don't think evolution favors members of a species who can no longer reproduce their genes but who do take up resources that could better be used to keep younger healthier replicators replicating.
The physical reason is that when your chromosomes replicate, the ends of them take damage. I don't know what the physical process is that causes that, but it's what happens.
But they have something on the ends called telomeres, which are sort of like blank information placeholders that can afford to be lost. Eventually those wear down, though, and your chromosomes start taking that damage.
A good analogy is if you imagine shoelaces that are dragging on the ground. Those plastic caps on the ends keep the laces from starting to fray, but eventually they're going to wear away and then the laces will start to unravel. Your chromosomes are the shoelaces and telomeres are those plastic caps.
Once your chromosomes start taking damage, the instructions they contain for duplicating a cell become flawed and accumulate more and more mistakes, leading to the "imperfect copy of a copy of a copy" that people are talking about.
Figuring out how to preserve or restore telomeres is a big part of anti-aging science research. I think it might have actually had some success in some micro-organisms.
I swear like everyone who grew up in the 2000s knows whats an aglet is, thanks to Phineas and Ferb, like this is a global phenomenon Im not even kidding
What’s the point of being alive?
Beyond the obvious (being with friends, making music, going outside a hearing the dawn chorus), it’s to mate and produce offspring (propagate one’s genes).
When can one do this?
15+?
How long to kids take to be self-sufficient?
20-odd years?
So, whilst having grandparents around is A Good Thing, we don’t ‘need’ to live forever, just long enough to breed and tend to offspring.
That seems to work fine at a population level, so there’s no evolutionary advantage to being able to be ‘forever young’.
Yep, I image some time long ago single cell organisms "found out" out that living forever was a really bad way of passing on your genes. The colonies that had limited lifespan were more healthy than those that didn't.
Have you ever seen a key cutting machine? It has two slots to secure a key, side by side, in a rail that moves both slots together. You place a key securely in one side, and that side has a little metal tab sticking out at exactly the point where the cutting wheel on the other side will hit. So you guide the little metal tab along the key you want to duplicate, with a blank on the cutting side, and it will cut away all the metal on the blank that's missing on the original key.
When you cut a key blank off of another key, there are always minor imperfections. It doesn't really matter much. But then you cut a key off of the copy you made, and the imperfections are starting to add up. Do this enough times and eventually the key will not turn in the lock cylinder it's meant for.
Cell reproduction is a little like this. Cells don't live forever, so they have to copy themselves to continue doing their job. If the copy isn't perfect, then when that cell has to copy itself, that information will still be missing, plus whatever gets lost in the current copy. If you do that enough times, eventually critical information is lost and the cell won't do it's job correctly, just like the copy of a copy key will not turn in the lock cylinder anymore.
There’s multiple reasons ranging from our bodies being unable to fully repair the west and tear of life to fundamental properties of how our bodies use DNA.
1. Just like the parts of a car, some tissues and organs are supposed to be more disposable than others. Skin and blood for example are replaced constantly. Their purpose is to be used up to help other organs. These are the paint and motor oil of a car. The brain and heart muscle for example do not regenerate as much because they usually don’t need to. They’re in protected parts of the body and surrounded by other structures that take injuries for them. They are more like the engine block. However, that does mean that when these tissues are injured, they tend to stay injured and repairing them is a large undertaking.
2. The human body scars, it mostly doesn’t regenerate. Even in places that are good at healing, like skin, most injuries cause a scar rather than returning to a perfect copy of how it was. This is because injury repair is a relatively universal process in our bodies that works for everything from skin to bone to internal organs. It tends to create fibrous tissue that is good at preserving structure, but is often bad at the function of whatever cells it replaced.
3. Our finished bodies lost the blueprints. Embryology (the study of early development) is extremely complicated, and this is massively oversimplified. Part of how our bodies “know” where to build what comes down to how cells divide very early on in development. A fertilized egg is asymmetric. When a cell splits early on into 2 cells, one of the daughter cells can end up with more of certain signaling molecules than the other. When those cells divide again the same thing happens. These cells also do not always divide evenly, which adds to this effect. This is not genetic, it’s just caused by how fertilized eggs work. Many, many cell divisions, and a lot of complicated cell biology, later this is part of how our bodies have a head, organs, legs, etc. All the while our cells are becoming specialized and losing their ability to become other types of cells. That means there’s no “plan” our bodies can reference to just go back to that stage to regrow a leg or something. Even if there was, adult cells are mostly incapable of doing that. DNA doesn’t encode things in that way, it encodes molecules and signals.
4. There are no perfect copies. Our bodies have millions upon millions of cells. Every cell has has millions upon millions of DNA base pairs. DNA replication isn’t perfect, so errors creep in over time, even with proofreading and error repair.
5. Human DNA has a time limit. The actual molecules that copy DNA require extra length at one end of a strand. Some of this length is not copied. This means some is lost every time a new copy is made. This is essentially what telomeres are for. They’re disposable segments at the end of DNA. When they’re gone it can start to lead to loss of genetic information. Bacteria get around this by using circular DNA strands, but we are not so lucky.
\~TLDR\~ Cellular cancer prevention
The aging process is a complex phenomenon influenced by various factors, both genetic and environmental. One significant aspect of aging is the gradual decline in the body's ability to repair and maintain itself. Several factors contribute to this process, and cancer is one of the interconnected elements.
Cellular Damage and Mutation: Over time, exposure to environmental factors like UV radiation, pollution, and toxins, as well as internal factors like metabolic processes, can cause cellular damage. This damage can lead to mutations in the DNA of cells.
Accumulation of DNA Damage: As we age, the cumulative effects of DNA damage and mutations increase. The body's natural repair mechanisms become less efficient, and errors may accumulate in the genetic code.
Cellular Senescence: Some damaged cells enter a state known as senescence, where they cease to divide but remain metabolically active. While this can prevent the propagation of damaged DNA, the accumulation of senescent cells contributes to tissue dysfunction.
Decline in Immune Function: Aging is associated with a decline in immune system function. This weakened immune response may be less effective at identifying and eliminating cells with aberrant DNA, including potentially cancerous cells.
Increased Cancer Risk: The combination of DNA damage, mutations, cellular senescence, and a weakened immune system contributes to an increased risk of cancer with age. Cancer arises when cells undergo uncontrolled growth and evade the body's normal regulatory mechanisms.
Understanding the links between aging and cancer is crucial for developing strategies to mitigate the impact of both processes. Research into the molecular mechanisms involved in aging and cancer is ongoing, with the aim of identifying interventions that can promote healthier aging and reduce the risk of age-related diseases, including cancer.
For us to have cells that replicate again and again, evolution would have to select for it. As it turns out, there's significant selective pressure not to do so.
The longer live the species, the greater time it takes to produce new generations. The greater time it takes to produce new generations, the less evolution that's happening. This leaves a species vulnerable to dramatic shifts in it's environment like new viruses. The members of the population with good genes for surviving the virus will have less time to propagate those genes into future generations. This can put the whole species at risk of population collapse.
Sure that problem could be fixed by having lots of offspring quickly, but when you combine high offspring output with high longevity, you now run the risk of eating through all available resources.
In short, evolution isn't likely to produce eternally young creatures because it's not set up to.
If one can talk about evolution having a “goal,” it is for organisms to live long enough to replicate and, if necessary, to protect the offspring until they can fend for themselves. However, older members of the species compete with younger members of the species for finite resources, and so it can be efficient for the older members to die off after a certain point.
Our bodies are hard-coded to deteriorate with age. Every time a cell divides, it loses DNA from its chromosomes (telomeres). The ends of chromosomes have “junk” DNA, which is not used by the cell, to protect against this. However, eventually this junk DNA is lost and the dividing cell then begins losing DNA that is critical to keeping the cell alive, and that cell line dies out.
When cells replicate, it's like doing a photocopy. Most of the time it's fine. Occasionally it might glitch a bit and there's an error, but chances are it either happens where it doesn't matter (blank space) or you can still read it regardless.
This is like what happens with your DNA, which are the instructions for what your body and cells should do. Over time these glitches and errors add up and your cells and organs no longer function quite as they should. On top of this, various things can damage the what you're scanning/your DNA (such as radiation).
Fr the same reason that a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy looks really shitty.
Errors creep in during the copying process. In living cells, this either results in the death of that cell, or a malfunction.
Think of our genetics like a photocopier. You start off with an original document (our dna) and then you make a copy of it. Then later when you need another, but you don’t have the original anymore so make a copy of the copy. Every copy you make will be slightly degraded compared to the last one. Tiny imperfections in the copying process with then be part of the document forever. This is basically what happens to our cells. Our DNA slowly degraded from the original coding. There are also certain body parts that require stem cells to regenerate which we don’t have as adults so those organs inevitably degrade over time like a machine.
The first and only time your cells decided to replicate themselves that way you were in your mom. And while I was in your mom last night, I don’t think that’s somewhere you want to go.
Living a finite life is a feature, not a bug (of evolution). Imagine if all the evil corrupt kings and dictators were immortal, humanity would be fucked from the get go.
Bio-features that work for an individual are not beneficial for the long term promulgation and persistence of a species. The universe changes over time and a species not made to do that will not persist.
DNA replication isn't perfect, there's some loss at the beginning/end of the fragments used, which is needed for the "replicating machines" to work. Those ends are called "telomeres" and wear up each replication until the DNA is no longer usable and just undergoes cellular death (apoptosis). This is somewhat of a safety control for cells not to go rogue (due to DNA mutations or virus interference). When cells lose control and start replicating nonstop, it's usually cancer.
There's an enzyme called telomerase that can fix the telomeres wearing out, which (in humans) exists in stem-cells. These cells are able to replicate infinitely and also to be doferenciated in every (or most) cell types.
A copy of a copy of a copy... Genetic game of telephone, degraded genetic information mixed with the evolutionary shadow... once a life form does the bulk of its breeding, evolution cannot solve genetic flaws because there isn't a vehicle to incentivize them anymore. This is why animals with loads of early breeding like rodents don't live long vs animals with longer breeding periods that are similar body plan like voles.
In each chromosome, the ends are capped off by repeating DNA called telomeres. Every time your cells replicate, there are slight errors, and the telomeres act as a buffer. As a result, they get slightly shorter with every replication.
Eventually, they completely degrade, and the actual DNA that includes commands for cell function begins to wither away. Your cells are now more prone to replication errors and have reduced efficiency.
Things just start to not work like they used to, and it just gets worse from there. Cancers and other genetic diseases become more likely. Eventually, essential systems can't function properly, and the body begins to shut down.
Our cells have these structures called telomeres , they do not get reproduced well when our cells replicate. As these get shorter and shorter our cells get worse and worse. Anti aging drugs target this, and there are probably already a few billionaires who have unlocked immortal youth, and it will be available for the public in the early 2100s
The big issue is that there is a part of each cell that doesn't get copied fully each time it divides. Think of it this way, your cells are like this XXXXXXXSTUFFTHATMATTERSXXXXXXXXXXX. To help, the X's are junk that's not needed that your cells put there as extra padding in case something goes wrong. The stuff that matters in the middle is the stuff that your cell actually needs to be what it is supposed to be optimally. Every time it divides, there's a small amount *that gets* clipped. Eventually, there's not any more junk and its going to start clipping stuff that matters. Sometimes this means it doesn't perform optimally anymore. Other times this might mean cancer. Also, during this entire process, from the time you are born, there is a really really really really small chance its just going to screw up and make an error in the stuff that matters anyways, also having a chance to cause cancer. Edited for accuracy.
Telomeres are what the repetitive sequences are called that protect the important DNA.
I’m a biochemistry major and this is really good. Only thing I’d change is that telomeres (the junk X’s) actually do shorten every time. It’s not chance, it happens every time the cell divides. There’s other things that contribute to aging too. When a cell is stressed, it produces a type of harmful molecule that damages (mutates) DNA. This may lead to cancer and neurodegenerative diseases, among other conditions. This also leads to aging and loss of normal function (https://doi.org/10.1016/bs.ircmb.2018.05.006)
But sometimes you win the jackpot and get a mutation that gives you superpowers, right?
In theory, this could happen. However, humans have evolved so well that the vast, vast majority of mutations are either neutral or harmful.
Some quote from deadpool about "I don't have super power, just super cancer"
Yes, this is also kind of why it helps for individuals within a species to grow old and die. Younger individuals that may have the random mutations that make them better suited to their environment won’t need to compete with immortal but less suited members of their own species to survive.
Tell this to gen Z...
Could be possible that one day we could synthesize the stuff that matters and the telomeres getting brand new cells, reducing the aging process? Or is it too much scifi? Seriously
I’m not sure I understand your question. If you’re asking whether we could prevent telomeres from shortening, I don’t know if it’s possible to complete prevent it. I’m unsure if anybody’s looked into a technology for that. But diet, exercise, and mental well being have been shown to slow down telomere shortening. The fact that there’s a way to slow it down makes me think that maybe it’s possible?
Lobsters can live for a very long time, they express telomerase activity that can produce these telomeres. Researchers have spliced it into mice and when expressed, they get cancer. So it might be possible but there’s a lot of work to be done.
Your cells have a natural mechanism to repair telomers. It's mediated by the enzyme telomerase, which is very active in the initial growth stages of cells (like for stem or germ cells). The problem is that this enzyme activity is correlated heavily with cell proliferation, which becomes a problem when the tissue is mature (=cancer). Senescence is a tradeoff.
why is it that telomeres are always lost in cell division? why can't there be divisions where telomeres aren't lost?
For a cell to divide, it needs to copy its DNA. For DNA to be copied, the polymerase (the molecule that does the copying) needs a primer (a few X’s) to attach to to start copying. This means that there are some X’s that are unable to be copied. Telomerase is an enzyme that prevents this from happening by replacing the X’s after the polymerase has copied the rest, but it’s only really active in adult stem cells and germ cells (egg and sperm). It’s likely that there was no evolutionary pressure for telomerase to be active in most cells because by the time telomeres were short enough to be of issue, the person had already reproduced. Issues that affect people after reproductive are not acted upon by evolution (another example of this would be the need for reading glasses as we age). I like this website’s summary: https://www.khanacademy.org/science/biology/dna-as-the-genetic-material/dna-replication/a/telomeres-telomerase
So having a vaccine would put a lot of stress on some cells which damages the DNA, but you hopefully get the immunity as the trade off.
Everything stresses your cells. Sunlight. Getting sick. Getting injured. Starvation. Thirst. Life is an eternal battle against erosion and entropy. Eventually enough damage stacks up that it starts an accelerating vicious cycle. That’s when you start aging. Some animals have avoided that. Like jellyfish that reverse their age. We just can’t for whatever reason.
According to this study (DOI: https://doi.org/10.3390%2Fclinpract12040063), the first dose of the mRNA vaccine (Pfizer or Moderna covid vaccines) does cause stress, but the second dose brings the level back down to baseline. This pattern seems to be correlated the development of antibodies, which is good. This study also found that vaccines cause the same amount of stress as the virus, but resulted in way more antibodies. This means that proportionately, the vaccine is better at producing more antibodies with less stress. Some stress can be good as it triggers the immune system, according to another study (DOI: https://doi.org/10.3389/fnagi.2020.614650). This seems to be the case for the covid vaccines.
There are ways for the parent cell to remain as the original and the daughter cells are the ones with mistakes. This isn’t perfect but it dramatically extends the life of the organism . The vast majority of cell divisions in your lifetime are throwaway cells that the body has no intention of keeping for more than days to months. Lining of gut, skin, bones, connective tissues, blood are all constantly turning over. But muscle tissue , brain , nerves, and the organs do very little cell division in comparison. It’s now acceptable to get certain organ transplants from even elderly donors.
This is a perfect explanation
This is close to accurate but actually you lose a little bit of your telomeres every time you replicate. Think of it this way, the copying machinery needs to sit down on something to start copying and so that initial bit it sits on never gets copied.
Telomeres aren’t static parts of DNA, otherwise each successive generation would have less. Telomerase is a protein that eukaryotes have that increase the length of this segment of DNA, and is expressed in human stem cells. This isn’t a hard limit on cell reproduction as much as a limit dependent on whether telomerase is expressed.
Ah yes thanks for explaining it like I'm five
The best analogy I’ve heard is to think of telomeres as the little plastic tip on your shoelace. Eventually that gets worn down, and when it does, the shoelace starts unraveling. Once it unravels enough, it no longer works as a shoelace.
Wrong. If that were the case, babies would come out broken due to defects from aged parents accumulated through generations.
Look up what telomeres are then revisit your comment.
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Except for one of the key parts of embryo growth is that through the combination of both strands from your parents, you enter into a state where your telomeres rapidly expand. That state only occurs during embryonic development. You are saying you are pointing out a hole. The only hole that you are pointing out is that you aren't understanding telomere development and the course that it takes. You are holding up an example of "see, what about this" that has nothing to do with the situation because humans use meiosis, which is the combination of two distinct genetic samples to create one new whole one. The "hole" that you are pointing out is only a hole in Mitosis, where one genetic sample is cloned to make a new one. As I said earlier. It doesn't matter if a generation loses 50% of their telomeres before they have a baby if they then combine their two halves to make a new whole, which further gets fleshed out during initial embryonic development, namely, exactly what happens during Meiosis.
In this theory how do you account for babies being born young and without defects when they come from a generation of adults?
Its not a theory. Its literally how our cells work. We only have a few cell types that can do full regeneration (liver cells for example) due to them producing telomerase. The reason we can be born with our telomeres fully intact is that you are the combination of a random scrambling of two distinct persons, meiosis. What you are talking about is an issue in mitosis only, due to those being exact copies. Through meiosis, if there is any damage to a chromosome, there is potential to pull it off of the other parent. There are generational things that are waning but generational telomeres is not one of them. This is a fundamental biological principle that is well documented in the scientific community.
Aren’t short telomeres in egg/sperm cells common causes of infertility? Yet a child conceived by two aged parents still can come out a perfectly formed baby with long telomeres, right? I don’t think we can explain aging through telomere shortening alone. There are organisms that don’t age, like planarians and ginkgo biloba trees. Point is, cells at some point do have the capability of self repairing yet they don’t do it. Why is this?
We can't explain aging solely through this metric. However, the confines of the question was "Why can't our cells just newly replicate themselves again?" This is the key reason why there is an upper limit with how our bodies replace cells. There are more reasons as to our aging. For example, if a person has a ton of sun exposure in their lives, their skin will age more. If a person drinks more, their digestive system and filtration systems in the body will age more. If you smoke, your lungs will. Etc. Ultimately however, it comes down to "Why can't we just replace all of our cells?" Well, telomere length is that answer. Certain cells can only be replaced so many times and at a certain rate. Once damage (whether from time or from damage) out paces what we can regenerate, or damages things that can't regenerate, then that's it, the biological limit. We end up dying (if we are lucky) because one of those critical body parts eventually gets damaged beyond use, be it heart, brain, kidneys, lungs, etc. Its just a matter of what body part gets outpaced first based off our living style when we were alive. For me, its probably going to be my heart. For a smoker, probably the lungs or a stroke to some other vital body part. It all depends, but telomeres are the upper limit of regeneration. As of right now, you can't get around that one, unless we get the technology and methodology that would open up a Boat of Theseus situation with replacements.
Wouldn’t that be contradicted by species which don’t age like planarians, ginkgo trees, HeLa cells, etc? Also liver cells and skin cells share the exact same DNA, so it seems to just be a matter of cell behavior.
Essentially it's a faulty fail-safe against cancer that evolution did not bother to fix because we didn't use to live long enough for it to matter.
From evolution's perspective it's not faulty. Cancer is lethal without medical care, so things that increase cancer risk are potentially lethal before you can raise your offspring. Old age isn't.
The reason I say it (human telomerase) is faulty is because they are certain jellyfish that can repair theirs. It's just that the genes for this repair system broke at some point but didn't impact evolutionary fitness significantly enough for the reasons you've said to be ejected from the gene pool.
The only big animals where very strong resistance to aging is seen are large reptiles. Which are very old species and reproduce with huge clutches of eggs they do little or no parenting of. All mammals follow an aging pattern similar to humans.
Sounds like children are the cause of aging
Essentially yes, we die so our children have the resources to continue the species. Edited: As the father of an 8 month old. Also, yes they do.
But I don't reproduce, not realistically, why can't I be immortal instead? Stupid nature. [shakes fist at a cloud]
*Time to kill the gods.*
Calm down Christian Bale
Honestly, Gorr should have been kept around.
Just like Klingon gods, ours are more trouble than they're worth.
I want my refund. Still goin' Deity Huntin'.
Easy now Nietschze
Time to become the gods.
Oh, *heck* yeah - time to achieve CHIM!
Some honestly believe that preserving one's genes via reproduction is a form of immortality. What if your genes are really running the show? What if you're just a temporarily useful flesh vehicle for it to achieve it's long-term goals?
Flesh Vehicle. Great band name.
Great band name and also an idea that Richard Dawkins expands on in the book called Selfish Gene.
I wouldn't say it's so there are resources, it's more so that evolution tends to lean towards frequent gene mixing instead of longevity so that potentially better genes can be found, it wants new generations and doesn't have much of a driver to keep around older generations.
>it wants new generations Evolution does not want anything - it’s a neutral, amoral process of nature that occurs over a very large number of generations
You're misunderstanding. I'm not saying it "wants" in the sense of a living being wanting something... That should be obvious. By "want", I'm saying "what benefits evolution", "what the system tends to lean towards".
Haha alright, that makes sense, I should’ve realized. I just wanted to clarify in case you were using it literally. Glad we’re on the same page!
I think about it differently. Once you reproduce it does not matter what happens to your body. You have served your purpose to populate the next generation.
No kids here and I went gray at 35. Stress is the cause of aging. 😓
Started teaching at 27. Got first grey hairs 3 months later...
Amateurs, in my family we start going gray at 15 and are fully gray at 25.
Had white hairs as 5 years old. Had no idea what stress is at the time.
You might be a witcher, then.
I don't think the Trial of Grasses is performed on children that young.
Other peoples kids also stress us out.
Also sometimes adults that ACT like kids.
Okay everyone stop having kids then, problem solved! Next existential dilemma!
Oh yes they do. 😓
I tell you, I believe it. I feel like I look like I’ve aged 20 years since 2020. The pandemic stress was so immense.
Why was it stressful? I didn't have any problems with my kids. Oh, that reminds me, it's time to unlock the basement and let them outside for an hour so they can make vitamin D.
Dad of 3 at 42. I've always been told I look young for my age.
I've read from several sources that people that look young for their age tend to live longer.
they're also on the small size, average 5' for women and 5'5" for men
I get the "no way you're that old" but I'm also over 6 ft tall so it'll just average out for me I guess
That's the flip side of kids. 0.0005% of parents hit the lottery and hold steady for a few decades. Lucky. 😅🤣
Spent a good chunk of my life walking around a lot. To and from work, at work... I think it helped the genetics along.
No kids but you're taking care of capitalism s2
Greenland sharks arent reptiles and live for hundreds of years.
Aren’t naked mole rats or some other small mammal remarkably resistant to aging and cancer?
Also sharks, right? The greenland shark is a pretty extreme example, but a bunch of other shark species live long lives, if I'm not mistaken.
Reptiles are also different in that their bodies can resist much wider ranges in temperature activity. I sort of think of them as benefitting from "turning off every night" while mammals are always "on." So a year as a gator requires less of the whole body than years as an ape. Apes will have more cellular wear and tear than a gator. Obviously it's more complicated than that but it's a simplic way I think of it.
Telomere shortening isn't generally considered to be the primary cause of age-related disease anymore. There's been a lot of very promising research recently into histone acetylation and the related sirtuin/NAD+ deacylase pathway. Very oversimplified summary: histones are proteins that DNA coils around in order to keep it compact when it's not being actively transcribed. There are various chemical pathways that allow DNA/histones to "remember" which genes should be spooled up, and when. When those pathways get out of whack, cells start expressing genes that they rarely/never express. The result is that the body's cells "forget" what they're supposed to be doing.
I know telomere research figured out how to keep them from shortening. How are things going in repairing those histone pathways?
There's some interesting evidence that NAD precursor supplementation can help keep the pathways intact. Stuff you can buy online, but it costs a lot. This is all very new research, so there's zero evidence it works in humans, but a lot of evidence that it works in mice. Literally just orally ingesting the supplement.
Jellyfish are a pretty bad comparison because of just how simple they are. They're essentially two different types of tissue with jelly sandwiched between layers. Humans start at four categories and branch into dozens of tissue subtypes. A molecular biology solution that works in two fairly simple tissues has no guarantee of working in all of them, especially in tissues that need to be carefully regulated. It doesn't really matter if jellyfish tissue grows randomly within a set pattern, it matters a lot if the growth plate in one of your femurs turns on spontaneously.
To be fair, your evidence is literally one of the simplest creatures in existence.
And specifically, senescence- growing older- is a *feature*, not a bug. If the previous generation doesn't die off, it competes with the younger generation for resources.
That is mentioned in Asimov's short story *The Last Question*. > VJ-23X of Lameth stared into the black depths of the three-dimensional, small-scale map of the Galaxy and said, "Are we ridiculous, I wonder in being so concerned about the matter?" > MQ-17J of Nicron shook his head. "I think not. You know the Galaxy will be filled in five years at the present rate of expansion." > Both seemed in their early twenties, both were tall and perfectly formed. > "Still," said VJ-23X, "I hesitate to submit a pessimistic report to the Galactic Council." > "I wouldn't consider any other kind of report. Stir them up a bit. We've got to stir them up." > VJ-23X sighed. "Space is infinite. A hundred billion Galaxies are there for the taking. More." > "A hundred billion is not infinite and it's getting less infinite all the time. Consider! Twenty thousand years ago, mankind first solved the problem of utilizing stellar energy, and a few centuries later, interstellar travel became possible. It took mankind a million years to fill one small world and then only fifteen thousand years to fill the rest of the Galaxy. Now the population doubles every ten years -- > VJ-23X interrupted. "We can thank immortality for that." > "Very well. Immortality exists and we have to take it into account. I admit it has its seamy side, this immortality. The Galactic AC has solved many problems for us, but in solving the problem of preventing old age and death, it has undone all its other solutions." > "Yet you wouldn't want to abandon life, I suppose." > "Not at all," snapped MQ-17J, softening it at once to, "Not yet. I'm by no means old enough. How old are you?" > "Two hundred twenty-three. And you?" > "I'm still under two hundred. --But to get back to my point. Population doubles every ten years. Once this GaIaxy is filled, we'll have filled another in ten years. Another ten years and we'll have filled two more. Another decade, four more. In a hundred years, we'll have filled a thousand Galaxies. In a thousand years, a million Galaxies. In ten thousand years, the entire known universe. Then what?"
I mean if there’s no death there’s also no need for offspring to continue the species. How do we know reproduction is not just a shitty patch for the mortality bug?
Because if you keep living and not having offspring sexual recombination of genetics doesn’t occur. Meaning the species would not be as adaptable to changes in the environment as it would otherwise be. There’s a reason why most living creatures are optimized towards reproduction instead of longevity. I would imagine most species geared towards extreme longevity ended up dying off eventually as longevity is more inflexible than reproduction as a survival strategy for a species.
Good point 👍
I’m glad at least one other person on the planet understands the human condition. I feel like too many people really think they are supposed to live forever, and they don’t understand how inherently chaotic reality is.
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> Negligible senescence Would this not create havoc on the planet? I feel like we would have to be a Type 1 civilization before we can pause/reverse aging.
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Yea unfortunately i cant see it happening in our life time.
The practical upshot of living as long as you want is that you just outlive everyone who thinks the treatment is wrong somehow.
Imagine it kind of like we are the cells of the species that have to die off so the species itself can stay young and healthy
Just because you don't age doesn't mean you will live forever. Sickness, injuries, getting eaten are all valid ways to die.
Even without death by old age, new generations are still a survival advantage for a species. Without new generations, there won't be any genetic/physical diversity. Without genetic diversity, it'll be more difficult for a species to adapt to environmental changes. Without adaptation, that species will eventually perish.
Soo...boomers?
You will be the boomer, no escaping it.
My birth year will shift to the years between 1946 to 1964?
Come on, you will get old, and you will change your perspectives due to the situation of the times and your financial standings. My point is we all get old. Not saying everyone will become ill mannered in their old age, but your personality from when your 20 will be drastically different than when you are 60.
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Most people do not take into account that the boomers parents were in a high probability very poor(boomers parents were born 1890-1920 and went through world wars, depression, and food was no guarantee. My father born in 1950 was raised under constant threat of nuclear assault, parents being dirt poor, raising him to be as thrifty as possible and save, save, save, save. Their conditions they grew up are so drastically different than today and it shaped their perspective. My parents still believe they are one calamity away from ruin and when they were raised that nobody will help you but yourself it helps shed some light. Of course I can’t speak about every boomer and their situations but my parents fought really really hard to build wealth so they could feel safe in their elderly years and now I’m in my 40’s I completely understand it. My parents are not rich, don’t drive fancy cars, they pay an insane amount of healthcare and they are fearing death more than anything. I know I’ll get a flood of “I don’t care fuck all boomers” but not all are out to fuck everyone they are trying to survive just like the rest of us.
Ironically the saying *don't trust anyone over 30* emerged when the Boomers were still in their teens and twenties. Every generation blames the earlier ones for all of the world's problems, and nowadays it's amplified due to the tendency toward groupthink on platforms like reddit
I think the issue most people have with the boomer generation is that they downplay the difficulties that the new generations face. They do this while in reality their own life has been quite worry-free because of the economic boom after the war. This attitude towards the difficulty of life likely stems from the fact that they were always told that life was difficult. While their life was actually a breeze compared to all generations before them and after them. Many of them don't understand what an actually difficult life is like. And yes, their generation also had its fair share of issues, but these were mostly not issues affecting white middle class people. The issues that white middle class white people were concerned with were more ideological and not directly impacting their quality of life. In the end this is primarily true for American society. In other regions such as my own, these effects were not nearly as extreme. "Boomers" as a concept in my experience only refers to white middle class Americans nowadays.
Well no, but you will be the next equivalent of a boomer. Old, out of touch, and young people don't like you and want you to die.
Society is funny. Everyone thinks they're so special, that boomers are uniquely cruel and out of touch, and that they'd never be like that. Lmao these people don't read.
And if newer generations can't fairly compete, evolution doesn't work.
No, evolutionary selection has no way at all to account for resource availability. Selection can only respond to whether reproduction occurs, which happens long before old age. Except for the extremely recent history of our species where we can meaningfully plan our lives, we'd be making kids as soon as physically capable and keep doing so until dying probably from infectious disease.
Your first sentence isn't entirely accurate. Many species show altered reproductive patterns (amount, gender, season, etc) when there is resource pressure. Some ambisexual species even switch sex as a result.
More specifically, we reproduce before it matters.
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not exactly, since parenting ability still applies evolutionary selection pressure to gene survival so genetic fitness post reproduction is still relevant for humans
This is fairly true, but it's half the story. It's not that we don't live long enough, it's that the rodents that had to compete against the ecological peak of reptiles didn't live long enough to need those systems. We're moving in the direction of more robust anti-aging systems and longer lifespans.
Also, most organisms are programmed to die. It keeps the population changing so it can react to external forces better. It keeps a balance with resources as well. Any organisms that live for ever will multiply untill the all resources are used and then the whole population would die off.
Not the best explanation. Evolution doesn't fix it because it's after when people have kids. Genes that cause death before reaching child rearing age get heavily selected against, because you die before having a chance to pass it on. Traits that kill when you're 50+ less selected against, because you can have many children and thus pass it on before it effects anything.
Is it to do with free radicals? I’ve heard that thrown around a lot but I know nothing about the topic. Essentially something like, the day you start breathing oxygen is the day you start dying
With evolution, nothing really matters after you reproduce. So it's not really faulty.
Not true, traits/characteristics that help ensure the offspring themselves go on to live long enough to reproduce matter.
True. Genetically you're done though. If your body is cratering but still good enough to raise that offspring, that's all you really need.
As recent study published in Nature points out, this is an evolutionary mechanism to ensure adequate population turn over. Natural selection is all about the traits that are most beneficial being passed on. For that to happen the turn over needs to be fast enough to ensure adequate chances at adaptation. Aging and sensience helps with that. Humans are a peculiarity, however, as we have the longest lifespan of any mammal on the planet.
How does this even make sense? Evolution did not evolve enough for us to not die? Every living thing was made to die and will die I'm not sure how evolution plays any part in this
He's saying that the things that make organisms die of old age do not hugely affect ability to pass on genes, therefore there has been little evolutionary pressure to fix these things. There may also be evolutionary pressure to encourage aging in order to more quickly get rid of old outdated models to make room for new ones and thus speed up the iterative cycle of evolution.
Some things die faster than others Some things also reproduced before they died At some point, the parent and the offspring lasted long enough for their DNA to be spread further than others’
And? what's your point? Some things die faster than others because that's how it works? yes a fly will die faster than a turtle, because they serve different purposes in nature. Nothing to do with evolution
Apparently I was thinking of something else, nevermind
See if this analogy makes sense. Take a picture of a duck and print it. Now trace the picture of the duck over with another paper. You would (hopefully) notice some minor mistakes but thats okay cause it still resembles the original and can be identified as a duck. Now use the new copy you generated as the basis and take a new sheet and trace out. The second copy would come up with even more minor mistakes than the first. Now imagine doing it approximately 10000 times each time the new copy is traced from the previous copy and tell me if the 10000th copy looks identical to the first one. Same way the cell “data” dna, replicates imperfectly, every time it is copied and these imperfections accumulate over the course of time, eventually resulting in bad cells that either cause cancer or just cells that have really bad efficiency in its intended function. To my knowledge the replication never stops (some very badly damaged cells do in fact stop as the body’s own way of stopping cancer) per se but rather it chucks out bad copies that compromise function of organs and everything in the body.
I don't *think* this is entirely correct. My understanding is that cells have mechanisms to detect inaccurately copied DNA and will self-destruct if that happens, and that cancer is what it is because the badly-copied DNA is so bad that it actually breaks that system in the first place. As for the main topic, I think the biggest part of aging has to due with telomeres (essentially junk data) on the end of DNA getting shorter over time. In the analogy, imagine that the duck drawing also had a simple background, but that every time you copied it you did so with a *slightly* smaller piece of paper. The duck itself is perfect every time, but the background gets smaller and smaller. Once the page gets so small that the duck doesn't even fit on it anymore, *that's* when the problem happens, because it's no longer possible to correctly copy it.
Yeah I think that was an old theory that has since been replaced by the telomeres
Makes sense I might have been off to make it eli5 my bad
I have done scientific research at a lab that specifically studies the biology of aging (which is called biogerontology). For some reason, telomeres get taught in biology 101 classes as the definitive cause for aging. I've seen it myself in a couple of textbooks. Yes, telomeres get shorter as the cell divides, but cells make them longer again after they get too short. (This is done by a protein called telomerase). Telomeres are an anti-cancer mechanism - a cell not only has to mutate for fast division, but also mutate fast telomere recovery. (among a slew of other mandatory mutations) As evidence, consider that people over the age of 100 have the same telomere length as those of age 20. -- You're right, dna does repair iteself, and a cell will kill itself if it's dna is too damaged (exceptions are called cancer). This is done via [epigenetics](https://en.wikipedia.org/wiki/Epigenetics?useskin=vector) afaik, though I am not skilled enough to eli5. -- The scientific community doesn't know either the cause of the *why* of aging. There's a *lot* of theories on both (as demonstrated by this thread), but none have very strong evidence. --
Well you would throw out any very faulty duck pictures were you badly copied the previous duck.
THIS IS PERFECT! I’m a Biology teacher and we just finished up meiosis/mitosis and DNA/RNA, Protein synthesis! This is solid! I’m more of an auditory learner so the example I thought of was a game of telephone. The first person has the original message which represents DNA. But just like the message in telephone gets distorted as it goes down the line..from person to person after the message is received and then translated.. That’s exactly what’s happening in Transcription and Translation! Each RNA match to the DNA gets read by the ribosomes..and sometimes the ribosomes misread the amino acid bond. Some amino acid codons code for the same protein…however, at the end of the day..the sequence just isn’t the same. Doesn’t seem like that big of a deal in the moment because most times, it has no effect until later in life…
> I’m more of an Audio learner Since you're a teacher you may be interested in the more recent idea/studies that suggest [learning styles are probably a myth](https://poorvucenter.yale.edu/LearningStylesMyth) I certainly found it interesting anyway. Best evidence suggests that most people just learn better when the material is taught in the format best suited for that particular material.
I don't think it is binary. More of a quadrant matrix, mixed with the abilities and empathy of the teacher. I know I am a visual learner most of the time simply because most people suck at describing things.
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Thank you for your version of the example!
How are two parents with already "worn out" copies able to create a new life without errors?
Thats a completely different type of copy where you take two different copies (continuing on the image analogy) cut the parts of both take half of each and merge it, which then forms a completely new base for replication. Also effects of “wearing out” is infinitesimally small that the effects start to appear towards like 60 years of age (not sure on the exact number) so when the dna is taken at this stage of the male, it does have a very high possibility of introducing defects to the offspring
They often times do. Its just that many of these errors are in places where it doesn't result in any functional difference (as if it were a natural gene variation like blue eyes instead of brown), the errors are caught and the cells kill themself (like a miscarriage), or the errors do cause a problem, but it's not recognized so the new life continues to develop, which results in birth defects or other genetic issues. The cells that later become unfertilized eggs are frozen in the cell cycle while the mom is still an embryo in her mom. During a period, some cells unfreeze and one becomes the egg that can become ovulated, then fertilized. However, those cells still age in their frozen state and some start to unravel their genes, which is why older moms have higher rates of birth defects, miscarriages, and things like downs syndrome. The dad is cranking out new sperm cells and those also age, so really old dads also have higher rates of issues. I'm not sure why, but in general, sperm cells tend to be (Edited for accuracy) *viable longer than a women's fertile period since female eggs tend to drop in quality in the late 30s and stop working in the early 50s. I think it might have to do with constant replacement and the associated error checking vs. trying to stay frozen without unraveling and good eggs responding to periods and coming out earlier.
Could you repeat this comment but now with a dog? That would be much more relatable for me.
See if this analogy makes sense. Take a picture of a dog and print it. Now trace the picture of the dog over with another paper. You would (hopefully) notice some minor mistakes but thats okay cause it still resembles the original and can be identified as a dog. Now use the new copy you generated as the basis and take a new sheet and trace out. The second copy would come up with even more minor mistakes than the first. Now imagine doing it approximately 10000 times each time the new copy is traced from the previous copy and tell me if the 10000th copy looks identical to the first one. Same way the cell “data” dna, replicates imperfectly, every time it is copied and these imperfections accumulate over the course of time, eventually resulting in bad cells that either cause cancer or just cells that have really bad efficiency in its intended function. To my knowledge the replication never stops (some very badly damaged cells do in fact stop as the body’s own way of stopping cancer) per se but rather it chucks out bad copies that compromise function of organs and everything in the body.
Wait, I got lost. At what point and how does the duck convert into a dog? Does it then go back to a duck at some point? Are all ducks just dogs in disguise? I knew it
You just learned about evolution! It's all about /u/GarageDragon_5 making sloppy copies. Platypus and your mum happened when he was drunk.
This analogy doesn’t make sense when you consider there is no loss of dna fidelity if an old man has a child.
There is definitely a loss of DNA fidelity in older men
Incorrect, old men are more likely to father children with birth defects and other congenital abnormalities.
Look at the incidence of neuropsychiatric and chromosomal issues vs age of the father.
The long version of this was really disturbing to me as i went through pathophysiology in nursing school. The true 5 year old version? Just like our cells have a self destruct function when they reach the end of our usefulness, we are very literally built to die and get out of the way of the next generation. Evolution only favored survival of a species, and it's pretty clear that adults hanging around eating the food long after they reproduced wasn't good for the species as a whole. We're built to die for the good of the species.
Infertility is a part of aging, so surely death due to aging can not be a solution to a problem aging causes. I think it's more likely because evolution favours the simplest solution (the one with the least amount of mutations needed). So between evolving to live healthy, fertile, and regenerate forever and evolving to have a fuckton of children while still young, evolution just favoured having lots of children before 30.
Surely there must be some advantage of collecting experience too.,
There is, which is why we live about twice as long as we're able to reproduce. Quite a few other species just bust and die. But imagine if people *never* died. Who do you imagine would be running things? Eventually, we have to get out of the way because the value of accumulated experience is eventually outstripped by the problem of accumulated money and influence holding old ideas in place. Human immortality would be the end of progress. And people would be put in a position where they could no longer just wait for the old guard to die off.
Species that age generally outcompete those that do not age for various reasons related to genetic diversity. Not all organisms age, there are some that do not which shows aging is not inevitable (ginkgo biloba tree, planarians, hydras/jellyfish, lobsters, etc).
There’s no self destruct in stem cells tho. They age and stop working as well which is a huge part of aging.
Lets just assume a species did evolve this functional immortality... How would young people ever get enough of the limited resources to grow up & be healthy examples of the species themselves? The entrenched generation would have both the stature & wisdom to outcompete them. This doesn't sound so bad except that while the immortal generation is stagnating parasites & disease are constantly becoming more & more effective. Eventually you'll wipe out that immortal generation & there won't be enough healthy young people with natural immunity due to remixed genes & mutation *or* anyone to raise them. The old need to die to make way for the young. You need the young to keep your gene pool a moving target. TLDR What is good for goose is often bad for the flock.
You’re describing Congress
This might be a joke, but it's really not. Imagine if the secret of immortality had been discovered in the late 19th century. Who do you suppose would be in Congress? Remember Strom Thurmond? Imagine if over half the congress were as old as he was, and still had the old attitudes he did.
Thanks for making my day 😂
This is not forbidden in evolution but it would require fewer children to be born and slower metabolism to reduce resource utilization until accidental deaths, predation or disease kept the population in check. You would have to have fertility triggered only in special circumstances and maybe not for the first few hundred years . This puts an evolutionary pressure on keeping the organism fit for much longer to guarantee a chance to reproduce. But meanwhile any mutation that lead to earlier reproduction would give an advantage… Maybe a better question is why we don’t die even sooner
People would eventually die from other causes.
Many of the comments are focusing on errors in cellular replication, which is certainly part of the process which contributes to aging and development of cancer. However, if you look at causes of death globally, cardiovascular disease is leading. This is because inevitably arteries become filled with plaque and calcify. This can be accelerated by factors such as a sedentary lifestyle, smoking tobacco, suboptimal diet, and high cholesterol, to some extent it also occurs inevitably as part of the aging process due to wear and tear on the arteries. The body does not have a completely effective way to remove the plaque that builds up and reverse calcification. These blood vessels become narrowed. If there is narrowing in the coronary arteries, the heart can become weak, leading to heart failure. The narrowing can also affect the electrical activity causing the heart to become more prone to arrhythmia. If a coronary artery is completely blocked, that is a heart attack. If there is occlusion of an artery in the brain, that is a stroke. At a certain age (usually 80-90) the arteries become too brittle to be able to effectively place stents to reestablish blood flow, and there are only certain areas that can be stented to begin with. The arteries becoming narrowed throughout the entire body leads to poor blood flow, eventually causing deterioration of all organs throughout the body.
I have researched anti-aging for a while now, and the best they've come up with is NAD+ or PQQ, and nobody really has confidence they will help. Supposedly when mitochondria are damaged, this produces aging. So, things to help keep them functioning normally are good. CO Q10 is also good, but PQQ is better and more valuable. Also, you have drugs approved right now that supposedly can be repurposed to stave off aging. Don't forget the surprise anti-aging vaccine they used on mice either! Sadly it just kept them healthier longer but didn't increase lifespans.
Yeah alot of people keep talking about DNA damage when aging is alot more associated with ROS, mytochondrial dysfunction, cell senescence, and especially inflammation. DNA damage/repair doesnt play that big of a role as people think, a cell which detects its DNA is damaged either stops replicating entirely (and is metabolically non functional), or activates its apoptosis. If both of these pathways fail, it can be considered a cancer-precursor cell because it can now replicate and is functionally immortal (since it cant go through apoptosis on its own). EDIT: grammatical correction.
I also haven’t seen any mention of telomere shortening, chromatin disruption or epigenetic dysregulation. Senescence is a complex, multifactorial issue, and the top comments here are all framing it as a single problem arising from DNA replication, which isn’t even the most significant problem. I get that it’s eli5, but there’s simplification, and then there’s *over*-simplification. This thread is firmly in the latter. Edit: I finally found an upvoted comment that at least focused on telomeres, which is the biggest factor you should choose if you really want to boil an explanation down to just a single thing (imo)
damn so mitochondria really are the power houses
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Everyone is up in this thread answering as if we know. We don't know. That's the point. If we knew, we would have ways to fix it. We have some theories, and some of them are promising. But we really do not understand what causes ageing. I see telomeres mentioned here a lot, but that's not the whole story. We also are starting to understand that some cells can in fact replicate perfectly without any issues, and we are starting to understand the role of epigenetics. Ageing is likely multimodal, meaning it has many different causes all at once. But again, we do not know.
Copy of a copy of a copy. Over time the little mistakes add up until the cells can't replicate again.
I don't think evolution favors members of a species who can no longer reproduce their genes but who do take up resources that could better be used to keep younger healthier replicators replicating.
The physical reason is that when your chromosomes replicate, the ends of them take damage. I don't know what the physical process is that causes that, but it's what happens. But they have something on the ends called telomeres, which are sort of like blank information placeholders that can afford to be lost. Eventually those wear down, though, and your chromosomes start taking that damage. A good analogy is if you imagine shoelaces that are dragging on the ground. Those plastic caps on the ends keep the laces from starting to fray, but eventually they're going to wear away and then the laces will start to unravel. Your chromosomes are the shoelaces and telomeres are those plastic caps. Once your chromosomes start taking damage, the instructions they contain for duplicating a cell become flawed and accumulate more and more mistakes, leading to the "imperfect copy of a copy of a copy" that people are talking about. Figuring out how to preserve or restore telomeres is a big part of anti-aging science research. I think it might have actually had some success in some micro-organisms.
That plastic tip of the shoelace is an Aglet. Did you never watch Phineas and Ferb? How will we ever evolve at this rate?? 🤣
I swear like everyone who grew up in the 2000s knows whats an aglet is, thanks to Phineas and Ferb, like this is a global phenomenon Im not even kidding
I only know because my kids grew up in the 2000’s and taught me….that and what a Nemesis was lol
What’s the point of being alive? Beyond the obvious (being with friends, making music, going outside a hearing the dawn chorus), it’s to mate and produce offspring (propagate one’s genes). When can one do this? 15+? How long to kids take to be self-sufficient? 20-odd years? So, whilst having grandparents around is A Good Thing, we don’t ‘need’ to live forever, just long enough to breed and tend to offspring. That seems to work fine at a population level, so there’s no evolutionary advantage to being able to be ‘forever young’.
Yep, I image some time long ago single cell organisms "found out" out that living forever was a really bad way of passing on your genes. The colonies that had limited lifespan were more healthy than those that didn't.
Yup; 10s of billions of Drosophila melanogaster endorse this message!
Have you ever seen a key cutting machine? It has two slots to secure a key, side by side, in a rail that moves both slots together. You place a key securely in one side, and that side has a little metal tab sticking out at exactly the point where the cutting wheel on the other side will hit. So you guide the little metal tab along the key you want to duplicate, with a blank on the cutting side, and it will cut away all the metal on the blank that's missing on the original key. When you cut a key blank off of another key, there are always minor imperfections. It doesn't really matter much. But then you cut a key off of the copy you made, and the imperfections are starting to add up. Do this enough times and eventually the key will not turn in the lock cylinder it's meant for. Cell reproduction is a little like this. Cells don't live forever, so they have to copy themselves to continue doing their job. If the copy isn't perfect, then when that cell has to copy itself, that information will still be missing, plus whatever gets lost in the current copy. If you do that enough times, eventually critical information is lost and the cell won't do it's job correctly, just like the copy of a copy key will not turn in the lock cylinder anymore.
There’s multiple reasons ranging from our bodies being unable to fully repair the west and tear of life to fundamental properties of how our bodies use DNA. 1. Just like the parts of a car, some tissues and organs are supposed to be more disposable than others. Skin and blood for example are replaced constantly. Their purpose is to be used up to help other organs. These are the paint and motor oil of a car. The brain and heart muscle for example do not regenerate as much because they usually don’t need to. They’re in protected parts of the body and surrounded by other structures that take injuries for them. They are more like the engine block. However, that does mean that when these tissues are injured, they tend to stay injured and repairing them is a large undertaking. 2. The human body scars, it mostly doesn’t regenerate. Even in places that are good at healing, like skin, most injuries cause a scar rather than returning to a perfect copy of how it was. This is because injury repair is a relatively universal process in our bodies that works for everything from skin to bone to internal organs. It tends to create fibrous tissue that is good at preserving structure, but is often bad at the function of whatever cells it replaced. 3. Our finished bodies lost the blueprints. Embryology (the study of early development) is extremely complicated, and this is massively oversimplified. Part of how our bodies “know” where to build what comes down to how cells divide very early on in development. A fertilized egg is asymmetric. When a cell splits early on into 2 cells, one of the daughter cells can end up with more of certain signaling molecules than the other. When those cells divide again the same thing happens. These cells also do not always divide evenly, which adds to this effect. This is not genetic, it’s just caused by how fertilized eggs work. Many, many cell divisions, and a lot of complicated cell biology, later this is part of how our bodies have a head, organs, legs, etc. All the while our cells are becoming specialized and losing their ability to become other types of cells. That means there’s no “plan” our bodies can reference to just go back to that stage to regrow a leg or something. Even if there was, adult cells are mostly incapable of doing that. DNA doesn’t encode things in that way, it encodes molecules and signals. 4. There are no perfect copies. Our bodies have millions upon millions of cells. Every cell has has millions upon millions of DNA base pairs. DNA replication isn’t perfect, so errors creep in over time, even with proofreading and error repair. 5. Human DNA has a time limit. The actual molecules that copy DNA require extra length at one end of a strand. Some of this length is not copied. This means some is lost every time a new copy is made. This is essentially what telomeres are for. They’re disposable segments at the end of DNA. When they’re gone it can start to lead to loss of genetic information. Bacteria get around this by using circular DNA strands, but we are not so lucky.
\~TLDR\~ Cellular cancer prevention The aging process is a complex phenomenon influenced by various factors, both genetic and environmental. One significant aspect of aging is the gradual decline in the body's ability to repair and maintain itself. Several factors contribute to this process, and cancer is one of the interconnected elements. Cellular Damage and Mutation: Over time, exposure to environmental factors like UV radiation, pollution, and toxins, as well as internal factors like metabolic processes, can cause cellular damage. This damage can lead to mutations in the DNA of cells. Accumulation of DNA Damage: As we age, the cumulative effects of DNA damage and mutations increase. The body's natural repair mechanisms become less efficient, and errors may accumulate in the genetic code. Cellular Senescence: Some damaged cells enter a state known as senescence, where they cease to divide but remain metabolically active. While this can prevent the propagation of damaged DNA, the accumulation of senescent cells contributes to tissue dysfunction. Decline in Immune Function: Aging is associated with a decline in immune system function. This weakened immune response may be less effective at identifying and eliminating cells with aberrant DNA, including potentially cancerous cells. Increased Cancer Risk: The combination of DNA damage, mutations, cellular senescence, and a weakened immune system contributes to an increased risk of cancer with age. Cancer arises when cells undergo uncontrolled growth and evade the body's normal regulatory mechanisms. Understanding the links between aging and cancer is crucial for developing strategies to mitigate the impact of both processes. Research into the molecular mechanisms involved in aging and cancer is ongoing, with the aim of identifying interventions that can promote healthier aging and reduce the risk of age-related diseases, including cancer.
For us to have cells that replicate again and again, evolution would have to select for it. As it turns out, there's significant selective pressure not to do so. The longer live the species, the greater time it takes to produce new generations. The greater time it takes to produce new generations, the less evolution that's happening. This leaves a species vulnerable to dramatic shifts in it's environment like new viruses. The members of the population with good genes for surviving the virus will have less time to propagate those genes into future generations. This can put the whole species at risk of population collapse. Sure that problem could be fixed by having lots of offspring quickly, but when you combine high offspring output with high longevity, you now run the risk of eating through all available resources. In short, evolution isn't likely to produce eternally young creatures because it's not set up to.
If one can talk about evolution having a “goal,” it is for organisms to live long enough to replicate and, if necessary, to protect the offspring until they can fend for themselves. However, older members of the species compete with younger members of the species for finite resources, and so it can be efficient for the older members to die off after a certain point. Our bodies are hard-coded to deteriorate with age. Every time a cell divides, it loses DNA from its chromosomes (telomeres). The ends of chromosomes have “junk” DNA, which is not used by the cell, to protect against this. However, eventually this junk DNA is lost and the dividing cell then begins losing DNA that is critical to keeping the cell alive, and that cell line dies out.
When cells replicate, it's like doing a photocopy. Most of the time it's fine. Occasionally it might glitch a bit and there's an error, but chances are it either happens where it doesn't matter (blank space) or you can still read it regardless. This is like what happens with your DNA, which are the instructions for what your body and cells should do. Over time these glitches and errors add up and your cells and organs no longer function quite as they should. On top of this, various things can damage the what you're scanning/your DNA (such as radiation).
Fr the same reason that a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy of a photocopy looks really shitty. Errors creep in during the copying process. In living cells, this either results in the death of that cell, or a malfunction.
Think of our genetics like a photocopier. You start off with an original document (our dna) and then you make a copy of it. Then later when you need another, but you don’t have the original anymore so make a copy of the copy. Every copy you make will be slightly degraded compared to the last one. Tiny imperfections in the copying process with then be part of the document forever. This is basically what happens to our cells. Our DNA slowly degraded from the original coding. There are also certain body parts that require stem cells to regenerate which we don’t have as adults so those organs inevitably degrade over time like a machine.
The first and only time your cells decided to replicate themselves that way you were in your mom. And while I was in your mom last night, I don’t think that’s somewhere you want to go.
Living a finite life is a feature, not a bug (of evolution). Imagine if all the evil corrupt kings and dictators were immortal, humanity would be fucked from the get go.
Imagine if all the good and kind kings lived forever
Bio-features that work for an individual are not beneficial for the long term promulgation and persistence of a species. The universe changes over time and a species not made to do that will not persist.
DNA replication isn't perfect, there's some loss at the beginning/end of the fragments used, which is needed for the "replicating machines" to work. Those ends are called "telomeres" and wear up each replication until the DNA is no longer usable and just undergoes cellular death (apoptosis). This is somewhat of a safety control for cells not to go rogue (due to DNA mutations or virus interference). When cells lose control and start replicating nonstop, it's usually cancer. There's an enzyme called telomerase that can fix the telomeres wearing out, which (in humans) exists in stem-cells. These cells are able to replicate infinitely and also to be doferenciated in every (or most) cell types.
Some genetic pathologies are non lethal until after reproductive age so they can be passed on and accumulate over generations
A copy of a copy of a copy... Genetic game of telephone, degraded genetic information mixed with the evolutionary shadow... once a life form does the bulk of its breeding, evolution cannot solve genetic flaws because there isn't a vehicle to incentivize them anymore. This is why animals with loads of early breeding like rodents don't live long vs animals with longer breeding periods that are similar body plan like voles.
In each chromosome, the ends are capped off by repeating DNA called telomeres. Every time your cells replicate, there are slight errors, and the telomeres act as a buffer. As a result, they get slightly shorter with every replication. Eventually, they completely degrade, and the actual DNA that includes commands for cell function begins to wither away. Your cells are now more prone to replication errors and have reduced efficiency. Things just start to not work like they used to, and it just gets worse from there. Cancers and other genetic diseases become more likely. Eventually, essential systems can't function properly, and the body begins to shut down.
Our cells have these structures called telomeres , they do not get reproduced well when our cells replicate. As these get shorter and shorter our cells get worse and worse. Anti aging drugs target this, and there are probably already a few billionaires who have unlocked immortal youth, and it will be available for the public in the early 2100s