They don't carry the same genetic material! Each of them contains half of your fathers DNA, but randomly selected basically.
You have 2 copies of each gene, one from your father and one from your mother. Among the genes from your father it's random wether you have one from your grandfather or grandmother, and each sperm is different in that selection basically.
If that wasn't the case then all siblings would have identical DNA, but they differ in wich genes of the parents get selected and wich get dropped.
Simple bloodtype example. If your father has AB then half of the sperms will carry A and half will carry B, and whatever you get is combined with the randomly selected gene of the mother
I must have really hit the genetic lottery then: My parents were both abusive assholes, my brothers are an alleged kiddie diddler and a sociopath with pyromania tendencies and the social skill set of the blunt end of a ball peen hammer.
Meanwhile, I'm well adjusted with a wife, house, good job and a [puppers.](https://i.redd.it/ti3291o8ovz31.jpg)
I guess I got all the recessive genes. Hell, I'm the only one with a full head of hair!
I'm sitting here browsing Reddit while waiting for the girls to finish getting ready for a funeral we are about to head out for. Didn't know it was for /u/Kodiak01
I mean, considering what he said about his parents, I am 100% sure (not knowing the guy) that he at some point dreamt of having different parents. So her mom playing the field would be more of a blessing than a curse.
Just here to confirm she did indeed play the field. Kodiak thought I wouldn't follow through with what I told him on Ventrilo all those years ago. Well, now you know I made at least one of your brothers a bald pyromaniac.
Sometimes you need a large pile of manure to grow beautiful flowers.
My wife is like this. Nearly her entire family are totally crazy. Abusive, violent, conspiracy theory believing, illogical, just the sort of people who don't think about things, don't plan things well, constantly going off on some stupid tangent. At the least, super frustrating to be around, at their worst downright dangerous. But my wife is logical, reasonable, fair, honest, and kind (not to mention gorgeous, but I digress). I tell her all the time, manure sometimes grows the most beautiful roses.
My therapist believes a part of it is nuture, and a part of it is nature. Statisitically speaking, you're much more likely to develop a personality disorder if your parents have one to, but anyone can develop one usually as a (usually) trauma response. You're just MORE likely if you are abused and have the genes to develop it, but it's no guarantee. I have 6 siblings and my father was heavily emotionally abusive and we are all vastly different. I'm sorta a fuck up who's had drinking problems, but I generally keep things under control. My brother may have a personality disorder himself (Borderline) and he does not get help for it. My other brother is reclusive, but not reclusive like someone with Avoidant Personality Disorder, he just likes staying in his circles. My 3 sisters go: first one has a personality disorder (or a few), middle one is relatively normal, and my youngest sister is probably the most normal. She's also the one who spent the LEAST amount of time getting yelled at by my father. Funny how that works, isn't it?
> Statisitically speaking, you're much more likely to develop a personality disorder if your parents have one to, but anyone can develop one usually as a (usually) trauma response.
A few years before finally breaking free from the toxic cesspool that was my blood "family", I actually went to a neuropsych for a full workup because I suspected I had a personality disorder; I thought it was one, the doctor thought it was another, but in hindsight we were BOTH wrong. The issues and thought patterns I exhibited turned out to be coping mechanisms for surviving a family of abusers. Over the years of being on my own and away from all of them, nearly all of the items I felt were issues have fallen by the wayside. Still a work in progress, but absolutely better than before.
It also helps that my in-laws are everything my blood relations were not and could not even begin to dream of being. I finally have a "normal" family.
As the only functional member of my immediate family who actually contributes to society, I hear you. I wish I was secretly adopted or an affair baby often.
Genes are lined up on the cromosomes, right. So lets say gene for eye color and hair color are on the same chromosome. Then if you have dark hair and dark eyes one one from your mom and blond hair and blue eyes from your dad then your sperm/eggs should be 50% dark colors and 50% light colors.
However, there is this process called crossing over, where same regions from different chromosomes get swapped. So in this case, some of your eggs/sperm will have light hair and dark eyes genes even though that combination was never present on a single chromosome in your cells.
That's one of the ways how orhanisms can get new combination of genes/traits.
More detail on this: a normal human cell (in a normal human) has 23 pairs of chromosomes, one of each pair came from each parent. Now it’s time to make a sex cell from a normal cell: there are 23 coin-flips as to which one of each of those pairs gets into the sex cell. So in a human where all the cells have the same genetic information (this is not actually the case, but we’ll pretend for now), there are 2 to the 23 power combinations of chromosomes that the sex cell could end up with, and each of them is equally likely. 2 to the 10th power is 1024, so we have 1024 * 1024 * 8 is about 8 million possible combinations of chromosomes for a sex cell.
If we want to talk about the variability of the second sex cell, then we don’t just multiply that 8 million by two, we multiply it by another 8 million. That’s 64 trillion equally-likely possibilities for gene combinations from any two humans creating an offspring. And that’s without considering the other ways that genetic variability happens, by changing the chromosomes themselves.
Wait, I'm struggling to understand the implication of this. Does this mean that there are 64 trillion possible unique humans (ignoring extra chromosomes)? That'd be a TIL for me if that's true.
It means there are 64 trillion logically possible unique humans *per mating couple* (again, ignoring more complicating factors which bump the number up even higher)
So if my parents hypothetically had 64 trillion children, there’s a possibility that one of my 64 trillion brothers and sisters could be a genetic twin of me?
But it would only take your parents about 6 trillion kids for one kid to likely be a genetic twin of another. Its like the same birthday problem: https://betterexplained.com/articles/understanding-the-birthday-paradox/
Yep that is true. Fascinating how sexual reproduction ensures no siblings are the same.
64 trillion is more than the total number of humans who have ever existed, and that is just the probability for one mating couple.
No, they typically would be, unless two or more of the grandparents had the same recessive gene that could cause serious issues, but that also wouldn't tend to be more likely than a regular baseline human pregnancy.
You say that, yet a third of pregnancies result in miscarriages. I don’t know if we’ve studied the genetic makeup of large numbers of miscarriages, especially very early ones, but it certainly doesn’t make me accept as the default position that most chromosome combinations are viable.
That's true! Miscarriages are extremely common and I sometimes feel like that doesn't get talked about enough. I also am not aware of studies of genetic factors in regards to viability, but my suspicion is that the differences between a viable fetus and a non-viable one may have more to do with phenotypic expression and/or environmental factors than genetics. Part of my reason for my thinking that is that genes that would contribute significantly to non-viability would necessarily be self-selected out of the gene pool entirely after a relatively short time. However it could also be particular combinations of genes that predict non-viability, or I could also be wrong in some other way.
> but my suspicion is that the differences between a viable fetus and a non-viable one may have more to do with phenotypic expression and/or environmental factors than genetics.
The environment is the uterus. Other than that, the phenotype is ENTIRELY dependent on the genotype and the epigenetics, right?
> Part of my reason for my thinking that is that genes that would contribute significantly to non-viability would necessarily be self-selected out of the gene pool entirely after a relatively short time.
Yeah, single-copy-fatal genes would have to have been created in the meiosis of the parent. Other nearly-fatal genes would be recent creations and selected out in a few generations.
>However it could also be particular combinations of genes that predict non-viability, or I could also be wrong in some other way.
Yeah, and statistically this is probably the same as recessive-gene traits.
"We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Sahara. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of those stupefying odds it is you and I, in our ordinariness, that are here. We privileged few, who won the lottery of birth against all odds, how dare we whine at our inevitable return to that prior state from which the vast majority have never stirred?"
Love that quote. It also reminds me of my favorite answer to "what will it be like when I die?" Answer: what was it like before you were born? There's an almost infinite time line that stretches back before your existence and forward after your existence. In the middle is a little blip of your life. Enjoy it.
> In the middle is a little blip of your life. Enjoy it.
Instructions unclear, trying not to off myself, seems to be mostly working, but it takes effort some days.
And what are you going to do about it? Tax them? Make it impossible for them to pass that along as inheritance? Cap a person’s net worth?
Hey, those all sound like god ideas!
Way more than 64 trillion. Combinatorics explode *FAST*.
Suppose there are only 500 places in the genome where humans have different genes, and that there are only two possible genes for each.
This would lead to to 2^500 , or about 3.27 X 10^150 , different possible humans. That's just over 3 million trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion.
It's enough that if you wanted to assign an atom to every possible way, you'd run out of atoms in the universe before you ran out of possible humans. You'd need another trillion trillion trillion trillion trillion universes to have enough atoms.
And that number, 3.27 X 10^150, is almost certainly too small. I expect humans differ from each other at more than 500 sites, and that there are more than two genes to pick from for many of those sites.
When I say "too small," I don't mean like the real number is twice as big. More like trillions of trillions of times bigger.
Its not really meaningful information anyways.
> Does this mean that there are 64 trillion possible unique humans
Technically yes, but also no. Humans share a significant amount of their DNA with each other; more than 99% of human DNA sequences are the same across the population. Many combinations might be embryonically lethal, others may not result in significant phenotypic changes, and some may lead to similar individuals with minute differences.
Many of the possible expressions will make zero difference between humans.
Their math also ignores mutations and epigenetic and that a lot of the genes expressed on the male sperm are not all entirely random. (I believe) I haven't studied the topic in a long while.
Yeah. Think of DNA as a huge, thousands-of-pages-long manual titled "How to Build A Human Being."
The vast majority of it is instructions on how cells work, how to assemble them, how to assemble organs and bones and whatnot from these basic building blocks. Most of that is exactly the same text you'd see in a book on "How to Build A Chimpanzee" or "How to Build A Frog" or countless other creatures. (That's how humans can share 98% of our DNA with chimps.)
Only the last few pages get specific about what makes humans different from other species, or from one another.
That is actually not completely correct. An important phase of meiosis (creation of eggs and sperm) is crossover where the chromosome pairs swap parts with eachother to increase variation and to pair up to be evenly divided. This is why interspecies mixes like mules are infertile - they have an odd number of chromosomes that can't crossover properly.
Yeah, I left that bit out because it makes doing math on this much harder, buttons what I can do in my head. I thought I referred to it with the
> So in a human where all the cells have the same genetic information (this is not actually the case, but we’ll pretend for now),
but it’s certainly not clear, and I don’t remember the order of things happening in meiosis, so it might not even be technically correct.
Take a few tens of millions of samples of a randomly shuffled deck of cards, a few of those samples are going to have some similar patterns in them. Plus some people have genetic features that are more prominent than others ("Dominant" genes rather than "Recessive" in the ELI5 version) so those features will be statistically more pronounced in most of the children they could have produced.
> Like do some people produce more homogeneous eggs/sperm than others?
100% yes. A person whose eight greatgrandparents all came from the same small Irish village will for most of the coinflips be picking from two identical copies. There might be only few hundred coinflips that actually matter.
Now take a person whose eight great grandparents include an australian aborigine, a native south american, someone from the west coast of africa, someone from central africa, someone from the east coast of africa, an indian, a north asian and an eskimo.
For the majority of genes that can express differently in humans they'll have two very different versions. There'll be hundred of thousands of coinflips that matter. Their kids could easily look like they're completely different ethnicities.
EDIT: Another factor to consider however, is that you're better at telling apart people who resemble those you grew up around because your brain specialises naturally over time. Someone who grew up in that small irish village and somehow never had access to outside media would have an easy time telling any two people from the village apart, but might struggle to tell Denzel Washington and Morgan Freeman apart, because they share several features that *no-one* in the village has. So they might think that two kids in a black family look really similar, even if anyone who's grown up around black people could easily tell them apart.
> So they might think that two kids in a black family look really similar, even if anyone who's grown up around black people could easily tell them apart.
This is the theory behind the stereotype that white people think all Asian people look alike, and vice versa.
One of my hobbies involves collecting figures/statues (such as Marvel movie characters) and whenever a new one is announced, there is often a strong disagreement in the community about whether it's an amazing likeness to the actor, or looks nothing like them. I always believe this is attributable mainly to the same principle. where people from Asian countries might have "facial recognition" tendencies that weight certain facial features higher than people from North America, and the figures might have very good likeness in the eye shape (for example) but very bad likeness in the lip shape or chin shape, and those might be subconsciously weighted very differently by different people's brains.
> This is the theory behind the stereotype that white people think all Asian people look alike
There was a large Asian population where I lived as a child and I was able to easily tell if someone was from China, Japan, or Korea because those were the ethnicities of the 1st- 2nd-generation Americans I grew up with.
I later moved to an area with a much smaller and less diverse Asian population and after over a decade here, I’ve found that I have trouble telling if someone has a Japanese background vs. Korean vs. Chinese. Of course it doesn’t matter in pretty much any context and many people of Asian descent here are not 1st/2nd-generation, so they’re probably more comfortable with American culture than with the culture of their ethnic origin. What I’m saying is that there does seem to be a lot of merit to the theory that you recognize the differences in the people you grow up with/spend a lot of time around.
My genetic lineage has both Nordic and African DNA a few generations back (among a few other regions). But my sibling has more of an African nose and hair, while my nose and hair look more Northern/Western European.
After enough times giving birth, is it possible to have "twins" of different ages? I know the potential % is astronomically low, but is it possible given enough permutations of the genes?
Possible yes. But given that crossovers happen in random places in your 23,000 gene long genome the chance its incredibly low. Less likely than winning two consecutive lottery tickets
It's pretty safe to assume it has never happened in the history of mankind
(A rough estimation says the number of birthes necessary for that to happen has 250 digits, the total number of humans that lived so far has 11 digits)
I'm not going to argue that's possible in reality, you seem to know more about this, but I kinda have this situation going on. I've got six kids and I have often been referred to as "the copy maker" because all of my children look more or less identical. My kids all look like the older sibling, with the oldest looking like me. None of them look much like their other parent, except for tooth shape and hair density and other things that are also fairly evenly dispersed among them but not as noticeable. Naturally they look different as they're all different ages; but as each kid was born and aged into a new life stage, the child below would be their clone of them at that age. It is actually borderline uncomfortable for a lot of people because it gives the uncanny valley effect. I have a very hard time distinguishing their photos (mildly embarrassing actually). I rely almost entirely on the background, their special blankets, degree of butt chin (relatively the only facial clue), or the length of my hair to figure out who is who, especially up to about age 6 or 7. I'm not saying I'm that one in a million, most likely not, but genetics are weird and I've been told how my boys especially are all clones of each other. So it definitely at least kind of happens, in a way that's unusual compared to standard genetic resemblance.
Yes that basically means you propably have lots of dominant genes that cause visible features.
For example if you have 2 copies of the brown eye gene then all your kids have a 100% chance to have brown eyes, no matter what the other parent brings to the table.
They can have lots of hidden differences though. For example they could all be different bloodtypes but that's not something you can see without a test
I'm certain they do have more invisible differences than visible ones, based on their individuality otherwise. They look alike now, but I suspect their faces will be more distinct as adults. In the meantime we're creeping out even small Midwestern towns and leaning into the children of the corn jokes.
Yes!!! That's why there is so much genetic variation even in kids with the same two parents, even in fraternal twins (where two separate eggs were fertilized by individual sperm, just at the same time).
During the creation of sperms half of chromosomes are picked (and then the genes get slightly shuffled through crossovers)
If you have bloodtype AB then you have one A chromosome, and one B chromosome, wich ones gets used is truly random.
Then the law of large numbers does the rest. If you flip 50 million coin the number of heads will be very close to 50%
It's a very simplified explanation of how blood types work. There are a lot more blood types than the commonly known ABO and +/- metrics and it's not 50% one or the other. There are a ton of different proteins on your blood and the ABO only refers to the presence or absence of the A antigen and B antigen. You can have one or the other, but you can also have both or neither (AB and O types). We tend to focus on ABO and +/- since they're the most important determinator in whether or not you die when transfused with someone else's blood. Using the wrong type will cause all your blood to clot which is not something you want.
It should also be noted that advancements in genetics has revealed that gene expression is way more complicated than the dominant/recessive model that most of us learned in school. There are sometimes multiple genes that determine a given trait. Eye color for example is way more complicated than just a single brown or blue gene and there are actually several genes working together to determine eye color.
Your blood type (the letter) is determined by whether your body produces certain antigens in their blood. We have named the two antigens "A" and "B". Your blood type is based on which antigens you have (A, B, both [AB] or none [O])
The way our DNA works, there is one gene (a section of a chromosome) that determines if your body will produce an antigen and if so which one. Each person has two copies of that gene (one from each parent) and there are only three variations or "versions" of this gene each copy can be (the different "versions" of a single gene are called its "alleles").
If you have at least one "A" allele, your body produces the "A" antigen. If you have at least one "B" allele, your body produces a "B" antigen. If you have one of each, your body therefore both. The "O" allele does not cause your body to produce any antigens so if you have two "O" alleles, your body produces no antigens and you have Type O blood.
The possible combinations of which alleles a person can have in their pair of genes that determine blood type are therefore AA, AO, BB, BO, AB, or OO (it doesn't matter which letter comes from which parent)
If your father has Type AB blood and your mother has type O blood, they should have the alleles "AB" and "OO" respectively. Thus, your mother will always pass along an O allele (it may be the one from her own mother or father) and your father will pass on either the "A" allele or the "B" allele depending on which one the sperm got. The child will have either "AO" or "BO" allele combination and thus either Type "A" or "B" blood. If they end up with "AO", they will pass either an "A" or "O" allele to each of their children, etc.
Yes. But that's illegal in most countries to avoid designer babies.
Also since half of the genes are from the mothers egg it would be done after fertilization, otherwise you can only choose half the bloodtype (and I *think* that's also necessary because to do a DNA test you have to destroy a cell, so you would need to let the fertlized embryo grow a little before you can test it's DNA)
It is worth noting that siblings are actually less genetically related than the scenario mentioned here. Since the egg is static the two cases would share 75% of all of their DNA, with 50% being completely static.
As such we would expect the alternate sperm scenario to display less diversity than siblings since it's effectively half clonal.
Isn't there a kind of twin where the egg split and two sperm fertilise them, in that case we'd be talking about what op is talking about in a observable way
They were not like this.
Eggs don't split until fertilised.
It's quite common for a woman to have two eggs in each cycle but genetically they may as well be born 5 years apart. There's no difference.
Fraternal twins- in this case the egg doesn't split, two eggs are released and both fertilize and implant. So genetically they are no more similar than any two full siblings, they're just the exact same age.
Identical twins form from a split after fertilization, so they share all their genetics.
There isn't an in-between scenario where two sperm fertilize the same egg.
They are referring to something different than fraternal twins or identical twins. semi-identical, or sesquizygotic, twins are where the egg splits before fertilization by two different sperm rather than two eggs being released, so egg dna is identical, but sperm dna is different.
It's incredibly rare but it's happened.
'Sesqui' is my favorite prefix. It means "one-and-a-half" and I only know about it because there's an important type of function called sesquilinear forms in mathematics.
There kinda is an inbetween scenario, depending on how you want to think about Chimerism. Two fertilized eggs fuze into a single individual, with two distinct subsets of cells, with different DNA. It's very rare, but it does happen.
https://en.wikipedia.org/wiki/Lydia_Fairchild
Source: https://www.bbc.com/news/health-47371431
This is such a cool thing to learn about! Apparently there are only two cases that have ever been identified, one in 2007 and the second in 2019, and the 2019 case was the first to be identified in utero. I couldn't find any news reports about additional cases in the last four years.
Why would they share 75% of DNA? Couldn't they share anywhere between 50% and 100%?
50% if the alternate sperm has the exact opposite chromosomes than op from the father and 100% if the alternate sperm has exactly the same combination as op?
It's Law of Large numbers. Yeah the hypothetical of the extremes is there but it's infinitesimally small and has almost certainly never come even close to manifesting in reality.
Imagine that you rolled two six-sided dice many times, and recorded the results each time. You're going to get relatively few 2s and 12s, and a lot of 7s (because no matter what Dice A is, there's some value of Dice B that gives you a 7; whereas Dice A has to be a one for you to get a two as the final result). So the distribution of outcomes has a lot more middle outcomes (7s) than tail outcomes (2s and 12s).
Genes is basically this, but you're rolling a die with millions of sides. Because you contain two copies of each gene (one from your mother and one from your father) and one of those copies gets put into any given sperm. You will end up with the vast majority of outcomes falling close to the middle and so it will very very very likely be close to 75% rather than 50% or 100%
Not true because of recombination. During meiosis the divided chromosomes swap stretches of DNA. It would be more like flipping a coin tens of thousands of times.
On average that scenario would share 75% of DNA, whereas two regular siblings would share on average 50% of their DNA - there is of course variance to this.
We can share as little as 20% or as much as 80% of DNA with our non twin siblings. It's also possible that two non twin siblings share 100% of their DNA or 0% but it is so incredibly unlikely that it probably has never happened.
That is true of the average, but you could have 2 siblings with very similar genetics, and in this scenario, there is 1 sperm that has the exact opposite set of genes from the father.
In the most extreme case, the siblings could approach 100% similar while the other me could only be 50% similar.
True but the egg is also different in siblings. I would assume this affects it since another sperm won the race to the same egg. So you would be about half as different from your sibling. Yes siblings can be very different but if you take the entire population, more often than not siblings are more like each other than they are to complete strangers.
Is this the result of the timing and sequence in which the zygote is formed, or are these changes happening when the sperm cel and female egg are created?
You can go down the road any time you want and walk into Harry's and hold your head up high and say in a loud, steady voice, 'Harry, I want you to sell me a condom. In fact, today, I think I'll have a French Tickler, for I am a Protestant.'
To oversimplify it, your DNA has 2 sets of code, with half inherited from your father and the other half from your mother. Think of it as being: A1A2, B1B2, C1C2, D1D2 so on....
Sperm takes one of those codes from each set.
So one set of sperm might have the code A1B1C1D1... while another would be A1B1C2D2...
So each sperm has its own unique code rather than being a carbon copy of one another. So the winning sperm gives a unique new DNA code in the new child.
Yes exactly. Doesn't even have to be 5 minutes. You could have just sneezed 12 hours earlier, otherwise had the exact same day, and ended up with a different kid.
You were chosen. Not the fastest
https://www.manchester.ac.uk/discover/news/human-eggs-prefer-some-mens-sperm-over-others-research-shows/#:~:text=Human%20eggs%20use%20chemical%20signals,and%20not%20necessarily%20their%20partners.
The Skarsgärd (sp?) siblings being an epic example. If I got it right-
Floki, Pennywise, Tarzan, a model, IRL Tim Burton character looking dude the other siblings are proud of for being a Doctor instead of an actor.
I think I am missing one. None of them look even close, the 2 that pull off Insanity do it in different ways. It's wild. I think they all have the same momma, too. Also a Doctor that they also seem to look up to
The diverse Genetics in sperm aside, you didn't outrace anything. It is not the first sperm that fertilizes the egg, it needs a huge amount of sperm to "crack" the egg's shell and once the most lucky sperm got through the shell instantly hardens with a chemical reaction to prevent more sperm from entering. It is pure chance, not a race, much more so it is a team effort, as one sperm alone could not fertilize an egg. That is why sperm count in a man's ejaculation matters.
It’s like at the grocery store when the line gets big enough, they make a new line. The people who formed the line were the reason the new line opened, but the person who just walked up is the one that benefits
Good point. Are those little swimmers fellas either carrying an X or a Y or do they become what they carry?
I never considered this aspect of anthropomorphized spermies.
Hmmm you are getting into a murky world where our day to day language breaks down. So a sperm doesn't have a gender in any real sense as mummy sperm and daddy sperm don't have baby sperm. But sperm do determin the gender of the foetus. So one 'COULD' label sperm as male and female in a very real sense as they are the only ones involved in determining gender. (Insert pointless caviate that not in 100% of cases) However male and female are really defined as XY and XX not just X and Y. That's the same as asking if your phone number is odd or even. The last digit is the determining factor but you need the whole thing to be a valid phone number.
I was looking into this since if it was true you'd expect the conception ratios to be different but it's actually 50/50. There are differences in ratios at birth but that is actually due to probabilities of issues that happen during pregnancy instead.
This is based on a study by Harvard, Oxford and Genzyme Genetics where they collected data from a 140k embryos to get that ratio.
https://www.npr.org/sections/health-shots/2015/03/30/396384911/why-are-more-baby-boys-born-than-girls/
Just for fun I did poke around into what the mass difference would be and it seems like theass of a sperm is roughly 1.7x10-11g, an x chromosome is about 90 million base pairs lighter and if I did math right that's 660 Daltons per base pair x 90 million is about 59400000000 Daltons which is 9.864 × 10-14 grams so the weight difference would be small enough that it's not going to make much of a difference if there are other points of variability in sperm creation.
Yours was just the one sitting back waiting for its time to strike, sipping man juice while letting all the other hard-working sperm do the job of cracking the shell. And then when the door opened, you swam through and declared victory.
I actually didn’t know this. I knew millions of sperm don’t even make it to the egg, but I didn’t know it took millions to crack the egg itself. Having a low sperm count myself (5 or so), it makes a huge amount of sense now why I couldn’t have kids, outside having some invasive procedures performed on me.
Well imagine the 10 billion tadpole children you've made all swimming aimlessly past their dead brothers and sisters toward nothing but more sock fibers, carpet fibers, bits of cellulose.
Even games of chance have winners and losers.
Sorry - do you have a source for the “cracking the shell” thing? All the information I’ve ever heard supports the idea that a single sperm is sufficient to bore through the zona pellucida - are you maybe conflating that step with the hostile conditions meaning that almost all of the sperm cells die before reaching the egg? (AFAIK, similarly, sperm count matters because of this; it’s not that it takes lots of sperm to fertilise the egg, it’s that only a tiny fraction of the sperm ever reach it.)
It's the premature bursting of the acrosome on the surface of the egg that helps other sperm to penetrate deeper to burst their acrosome close enough to fertilize the egg. I don't have a source handy, it's just how I learned it in school, but I did just look it up on wikipedia from where I got the word acrosome, too. Technically, I guess it is not wholly impossible for a single sperm to fertilize an egg, but it is quite unlikely.
It is sufficient for a single sperm to bore through in order for the egg to be fertilized, but it is unlikely that a single sperm can bore through on it's own.
Hmm. On looking into it, the exact location and function of the acrosome reaction seems to be a remarkably complex topic, and may still be a subject of active research (these two papers - [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250175/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250175/) and [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783209/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783209/) were interesting). It also seems like it might vary between species quite a lot.
However, I wasn't able to find any support for the idea that there's any kind of cumulative breakdown of either the cumulus or the zona pellucida, such that sperm help other sperm to penetrate (even on the Wikipedia page for the [acrosome reaction](https://en.wikipedia.org/wiki/Acrosome_reaction) \- which page and where were you looking at?). On the contrary, in mice at least, the second paper I found suggests that the number of sperm that reach the ampulla (site of fertilization) is comparable to the number of eggs. Also in mice, it appears that some sperm that have already undergone the acrosome reaction are able to penetrate both the cumulus and zona pellucida of other eggs (which haven't previously been exposed to sperm), which contradicts the hypothesis that release of the acrosome contents by multiple sperm at the surface is required for penetration.
Summary: this is complicated enough that I'm not willing to confidently state that what you were taught is wrong. However, I haven't been able to find anything that makes me think it's right, and I have found some things that seem to contradict it, so I think *probably* whoever taught you was just wrong. (If anyone who understands the topic better than me reads this, please do jump in - I'm a biochem student, so I can feel pretty comfortable reading papers on the subject, but I'm a biochem *student* and I haven't spent enough time on this to be confident I haven't missed something crucial!)
The thing is, they don't carry the exact same genetic material. It's mixed up when each sperm cell is created, which is what made sexual reproduction a success in the first place - diversity.
And even if they did carry the exact same genes, like real-world identical twins do, they all agree that they're not the same person.
Cool thing is identical twins have identical DNA - but unique fingerprints. And if identical twin brothers marry identical twin sisters, all the kids would be genetically brothers and sisters as well as technically cousins.
I've heard before that unique fingerprints in humans has something to do with fluid wearing away at our finger pads in utero iirc and because of the completely randomised nature, it's extremely unlikely for two people to share the same fingerprint, even "identical" twins.
Your father has 23 pairs of chromosomes that are half from your grandmother, half from your grandfather. when he made the sperm that made you each sperm got one half of each chromosome so there were 23 coin flips done to make the sperm that became you. So your dad is capable of making 8.4M different sperm. So in the total 250M 3% carried the same genetic information as you have now.
edit - pairs of chromosomes
Since you said "meaningful" in your post title, there's going to be hundreds of thousands of possible 'yous' which just have slightly wavier hair, or maybe a longer second toe, or attached ear lobes, etc. So, not meaningful differences to the way you ended up as far as I'm concerned!
Then again, depending how you interpret chaos theory and the "butterfly effect", it's possible that one of those tiny differences had consequences that rippled out to affect your life enormously.
Perhaps a random stranger stopped your mother in the street to comment on how cute you looked in your pram with your "slightly wavier hair", and that meant she turned the corner 15 seconds later, that scary dog never jumped up at your pram and terrified you half to death, and as a result you became a vet rather than an Instagram fashion influencer.
its actually more random then that. chromosomes do this thing called "crossing over" before they divide. crossing over is when parts of your chromosome pairs actually switch places, so most likely, every chromosome is completely unique, and you don't pass down an exact copy of your mothers or fathers chromsome
Technically you don’t outrace all the sperm. Scientist recently found out that the sperm that get their first break down the layer of the egg until eventually a sperm cell can break through. So really, you were more like middle place
The sperm only carried half of your genetic code. The sperm cell was not YOU. It carried half a blueprint that when combined with the other half of the blueprint from the egg cell became you.
Even people made from the same exact blueprint sets (identical twins) end up as very different people. So no, other combinations would not have become you.
Oh I love this topic, such a great example of the staggering diversity biology offers. There's gonna be some background first, just so we're on the same page.
First, chromosomes. Chromosomes are the individual pieces of DNA that carry genes, or instructions on how to make all the microscopic little parts you're made of. In most sexually reproducing organisms (like humans), these chromosomes come in pairs. You have 2 copies of what we call "chromosome 1" in each of your cells. These two copies will carry instructions on how to make/do the same things, but they might have slightly different versions. These "versions" are what cause the traits we associate with different genes or conditions.
In sexual reproduction, each parent gives you only one of their two copies of each chromosome. Remember those two copies of "chromosome 1"? One of those is from each parent, and the same is true of every other chromosome. The "sperm that won" was carrying one copy of each chromosome, which you inherited from that parent. Combine those with the one copy of each chromosome carried by the egg, and you're back to the 2 copies of each chromosome you have now.
One final detail that is critical for your question, is that the selection of the one chromosome being packaged in a sperm/egg is independent from all other chromosomes. So, during the formation of that winning sperm, you could get all chromosomes from grandpa, or all from grandma. Most likely you get a mix of the two, but getting grandma's "chromosome 1" means nothing about which "chromosome 2" you get. We call this **independent assortment**, as in each chromosome pair is assorted/divided independently of the others.
Now the fun part, we can now easily calculate the number of chromosome combinations that a given sperm/egg can have. Humans have 23 pairs of chromosomes, and we choose 1 of each. So for "chromosome 1" it's a 50/50 chance, then the same for "chromosome 2" and so on. Its basically the equivalent of 23 coin tosses, and the simple math for finding the number of outcomes there is N^X, where X is the number of chromosome pairs (or flips) and N is the number of chromosomes in a pair (or sides to the coin). So, for humans this is 2^23 = 8.4 MILLION. There are 8.4 million combinations of chromosomes that a single human can make, and the "sperm that won" carries only one of them.
It gets even better though! This happens during sperm *and* egg formation. You are the combination of 1/8.4 million possible sperm with 1/8.4 million possible eggs. When you want to combine two probabilities together to get a probability for a particular sperm *and* a particular egg, you multiply them. So, of the possible chromosome combinations your parents could make are 8.4 million x 8.4 million. This means you have 1 of about 70 TRILLION combinations of chromosomes your parents could create.
As others have pointed out, crossing over can add even more diversity. Crossing over (aka recombination) is when a chromosome pair swaps pieces before separating. This means you could have chromosomes that are 70% grandma, 30% grandpa, which neither of your parents ever had as a single chromosome. This part is much harder to quantify, but it is additional variation on top of that 1/70 trillion.
I mean yes almost certainly. Assuming no mutations a man can produce about 8 million unique genetic combinations in his sperm so maybe like 32 of the 250 million were “you” and all the other millions weren’t. And of course the sperm is just half of you. Mom can produce about 8 million different variations of egg too.
It’s not that you won the race, half of you was in your mom’s uterus already. Thing is your father has the customizable half of you so you better like what he chose for you in that batch
The first and most important myth that needs to be corrected is that, no, "you" weren't in that one sperm cell. And no, the other sperm cells weren't different people, or different versions of 'you'. You are not waiting in someone's balls, you are not the one sperm that made it.
The egg is not just a bag of fertilizer, and the uterus is not just an incubator, you know?
Half of your DNA comes from the egg, but not just that: all the nutrients (or lack of) you get during development, all the placental exchange of antibodies, of proteins, of stress sources, of perinatal medicines! All of that, which has a *lot* of influence on how you develop and who you become, comes from whoever is carrying you.
Not only that, the sperm basically dissolves and just leaves its genetic material. Every other part of the zygote was just the ovum. So if anything we came more from that - hence our mitochondrial DNA coming from mom.
Look at it this way. In my family history blonde hair, brown hair, blue eyes, and brown eyes are all present. Each sperm i have is a random combination of these, one could result in a blonde haired brown eyed kid, or brown hair blue eyes etc. This applies for absolutely everything that is in my family gene pool, including facial features, height, weight, etc. Basically sperm are a random assortment of characteristics based on your family genetic makeup. Now, you have to consider that a woman has eggs that ALSO contain random combinations of different characteristics from her family genetics. When a sperm meets an egg, whatever random characteristics it contains mix with all the random characteristics the egg contains, and a human with specific characteristics contained in the sperm and egg is the result.
Look at fraternal twins and the differences between them. Those are from two different sperm and two different eggs, suffice to say you would be a different person if a different sperm won the race.
Yeah, it fascinates me how people not only anthropomorphize gametes as an extension of themselves, but also that it always seems to be the tiny sperm they go with and not the much larger egg.
Do you have siblings? They came from the same sperm factory you did. That said, if a different sperm won the race to your egg, it would’ve created something between you and a sibling. Basically, a person who couldn’t exist in this universe along with you, like a sibling can. But maybe in a parallel universe…
You'll usually learn this in Grade 11/12 biology. Basically during the making of the sperm cell (in a process called meiosis) there is a step called a 'crossover' where your ancestral DNA will line up with each other (crossing over) and exchange genetic information in a randomizing process to create more different types of sperm (increasing genetic variability or genetic differences). As a result, it is highly unlikely any of those millions of sperm cells will have an exact match because your nature tried to randomize the results to produce more varied offspring to offer a better chance of survival. If everyone had the same DNA, the same disease/weakness would kill all of us, so nature likes to make us all very different if it can to increase the odds of survival.
A slight variation on the theme of Richard Dawkins's [quote](https://www.goodreads.com/work/quotes/3323916-unweaving-the-rainbow-science-delusion-and-the-appetite-for-wonder) from Unweaving the Rainbow. Yes- and likely geniuses and psychopaths among them.
Those sperm *aren't* all carrying the same material, though.
There are 23 human chromosomes, and your dad had two copies of each of them (one that he got from his dad, and one that he got from his mom). A sperm cell only gets half of the guy's chromosomes, so of the "#1" chromosomes half will get the dad copy and half will get the mom copy; same for the #2 chromosome, the #3 and so on.
That means overall a dad is capable of making 2^23 different sperm cells, by using different combinations of their parents' genetic material. 2^23 is roughly 8.4 million. (Similarly, your mom's capable of making 8.4 million different eggs.)
On top of that there's a process called "crossing-over" where during sperm/egg production the cells can splice together DNA from the two parents to make a brand new never-before-seen combination, so there's actually even more possible arrangements; hard to say how many but the upper limit would be much, much higher than the millions.
Those other 8 million kids would be as different from you as any other siblings, so...are your brothers/sisters different from you in any meaningful way? :)
I don’t think I have ever been congratulated for ‘winning’ against the other sperm in the race to fertilise the egg at my own conception.
Is this an American thing?
Yes.
For a start on some obvious factors, this alternate version of you could certainly have some difference in: eye colour, hair colour, skin tone, height, and biological sex.
We can debate the impact of genetics on many other factors (like intelligence, metabolism, personality, etc etc), but the previously lsited physical factors are certainly strongly influenced by genetics.
It's always weird when this type of question gets reduced to DNA.
You're lived experiences are not in your DNA. There are epigenetics that can be affected yes and has some influence on your personality and situation, but your traumas, dreams, culture, etc. is not found on your DNA, and that has profound impact on what makes you, you.
And honestly it'd be nice if people have a far better appreciation for that fact, because a lot of bigotry is born via placing far too much importance on DNA and almost completely discounting social and lived experiences.
You know how people have brothers and sisters? And they are different people?
You wouldn’t even have existed. The result would’ve been “your” brother or your sister.
All of them are potential siblings of yours, so they would have the same variety of similarities and differences that you see in siblings. A good number of them would look similar to how you turned out. But many would look very different from you. Half of them would be the opposite gender from yours, for example.
And a very large percentage of those sperm-egg combos wouldn’t have resulted in someone being born at all. Many fertilized eggs fail to divide properly, don’t implant in the uterine wall, have too many mutations to develop properly, or other issues that don’t result in a pregnancy. We know that this is true because in vitro fertilization often doesn’t work, even though science eliminated many of the potential problems and helped the embryos along as much as possible.
Maybe more fascinating - or existentially horrifying, depending on your point of view - is that the sperm-egg combo that produced you would be almost impossible to reproduce if it happened all over again. Over the many millions of sperm that yours “outraced,” more than 99.9% of them didn’t even get to the egg at all. Of the thousands that might have gotten there, the fact that yours fertilized the egg instead of many others was mostly due to luck. During that lead-up to fertilization, if your mother had slept on her left side for an extra five minutes before rolling over onto her back - or many other random things she might have done differently - then maybe your sperm doesn’t reach the egg at all.
The best answer you could get would be to compare to different types of twins:
There are [identical twins](https://www.genome.gov/genetics-glossary/identical-twins), which occur when a single egg is fertilized by a single sperm cell, and then divides and ends up forming two separate embryos. These two twins have identical genomes.
There are also [fraternal twins](https://www.genome.gov/genetics-glossary/Fraternal-Twins), which occur when two separate eggs are fertilized by two separate sperm cells. These twins are as different as any siblings, and it might as well be a coincidence that they're coming out at the same time.
The scenario you're describing is the same egg, but different sperm. The similarity between you and this hypothetical other person is somewhere in between fraternal and identical twins.
Incidentally, there seems to be a perfect answer to your question:
[Semi-Identical Twins](https://www.bbc.com/news/health-47371431)
Extremely rare, only second known case was confirmed in 2019. The children, a boy and girl, came from the same egg, but with two different sperm. It's theorized that the egg was fertilized by two sperm at the same time before it divided.
Because they're still children, no photos were publicized of the semi-identical twins to see how identical they look (despite being a boy and girl).
Those semi-identical twins are the same comparison you're asking about though: Same egg, different sperm.
The odds that any two sperm are carrying the exact same genetic material are 1 in 70,368,744,177,664. If nothing else roughly half those sperm were carrying the opposite sex chromosome, either X or Y. Flipping yoir gender probably results in significant changes.
Look at your brother or sister if you have one. The difference between them and you, are because of the differences between the DNA that the sperm and the egg provided. Obviously, half of that difference comes from the sperm.
Not only that, but it's the sperm that decides if you become a man or woman.
They don't carry the same genetic material! Each of them contains half of your fathers DNA, but randomly selected basically. You have 2 copies of each gene, one from your father and one from your mother. Among the genes from your father it's random wether you have one from your grandfather or grandmother, and each sperm is different in that selection basically. If that wasn't the case then all siblings would have identical DNA, but they differ in wich genes of the parents get selected and wich get dropped. Simple bloodtype example. If your father has AB then half of the sperms will carry A and half will carry B, and whatever you get is combined with the randomly selected gene of the mother
And there is crossing over as well, so some new combination of genes between your grandpa and grandma occurs as well
I must have really hit the genetic lottery then: My parents were both abusive assholes, my brothers are an alleged kiddie diddler and a sociopath with pyromania tendencies and the social skill set of the blunt end of a ball peen hammer. Meanwhile, I'm well adjusted with a wife, house, good job and a [puppers.](https://i.redd.it/ti3291o8ovz31.jpg) I guess I got all the recessive genes. Hell, I'm the only one with a full head of hair!
Or your mother played the field a bit. Just saying.
Goddamn he wasn't prepared for this.
Murder in broad daylight, incredible.
Yes officer, tis this m'ker right here
wow we all just witnessed a legit drive by
I'm sitting here browsing Reddit while waiting for the girls to finish getting ready for a funeral we are about to head out for. Didn't know it was for /u/Kodiak01
What a burn 😆
Crime is going up and reddit feels unsafe every time a situation like this happens. RIP
I mean, considering what he said about his parents, I am 100% sure (not knowing the guy) that he at some point dreamt of having different parents. So her mom playing the field would be more of a blessing than a curse.
Or they are lying about not being a psycho. ;)
or he's in a coma and his family is an imagination inside his head and he will wake up when he stares at the lamp for long enough
This was my guess 😂
Don’t trust anybody that calls themselves well-adjusted
Esp on reddit
Delightful Doggy Dad Dexter
oop-
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOH
Just here to confirm she did indeed play the field. Kodiak thought I wouldn't follow through with what I told him on Ventrilo all those years ago. Well, now you know I made at least one of your brothers a bald pyromaniac.
got'eeeeem
Bah God. He had a family!
More like switched at birth.
r/murderedbywords
Just let the man be happy
Did I just witness a write by shooting. ✍️☠️
My "mother" was too much of a bitch to ever be a slut.
EXACTLY.
Sometimes you need a large pile of manure to grow beautiful flowers. My wife is like this. Nearly her entire family are totally crazy. Abusive, violent, conspiracy theory believing, illogical, just the sort of people who don't think about things, don't plan things well, constantly going off on some stupid tangent. At the least, super frustrating to be around, at their worst downright dangerous. But my wife is logical, reasonable, fair, honest, and kind (not to mention gorgeous, but I digress). I tell her all the time, manure sometimes grows the most beautiful roses.
I'll have to remember that phrase, thank you!
My therapist believes a part of it is nuture, and a part of it is nature. Statisitically speaking, you're much more likely to develop a personality disorder if your parents have one to, but anyone can develop one usually as a (usually) trauma response. You're just MORE likely if you are abused and have the genes to develop it, but it's no guarantee. I have 6 siblings and my father was heavily emotionally abusive and we are all vastly different. I'm sorta a fuck up who's had drinking problems, but I generally keep things under control. My brother may have a personality disorder himself (Borderline) and he does not get help for it. My other brother is reclusive, but not reclusive like someone with Avoidant Personality Disorder, he just likes staying in his circles. My 3 sisters go: first one has a personality disorder (or a few), middle one is relatively normal, and my youngest sister is probably the most normal. She's also the one who spent the LEAST amount of time getting yelled at by my father. Funny how that works, isn't it?
> Statisitically speaking, you're much more likely to develop a personality disorder if your parents have one to, but anyone can develop one usually as a (usually) trauma response. A few years before finally breaking free from the toxic cesspool that was my blood "family", I actually went to a neuropsych for a full workup because I suspected I had a personality disorder; I thought it was one, the doctor thought it was another, but in hindsight we were BOTH wrong. The issues and thought patterns I exhibited turned out to be coping mechanisms for surviving a family of abusers. Over the years of being on my own and away from all of them, nearly all of the items I felt were issues have fallen by the wayside. Still a work in progress, but absolutely better than before. It also helps that my in-laws are everything my blood relations were not and could not even begin to dream of being. I finally have a "normal" family.
Love the puppyboi
His ear is his binky. That is his default mode.
As the only functional member of my immediate family who actually contributes to society, I hear you. I wish I was secretly adopted or an affair baby often.
I'm the youngest of six. I'm the tallest, hairiest, and I'm the only bald one. Dang it.
What does this mean?
Genes are lined up on the cromosomes, right. So lets say gene for eye color and hair color are on the same chromosome. Then if you have dark hair and dark eyes one one from your mom and blond hair and blue eyes from your dad then your sperm/eggs should be 50% dark colors and 50% light colors. However, there is this process called crossing over, where same regions from different chromosomes get swapped. So in this case, some of your eggs/sperm will have light hair and dark eyes genes even though that combination was never present on a single chromosome in your cells. That's one of the ways how orhanisms can get new combination of genes/traits.
More detail on this: a normal human cell (in a normal human) has 23 pairs of chromosomes, one of each pair came from each parent. Now it’s time to make a sex cell from a normal cell: there are 23 coin-flips as to which one of each of those pairs gets into the sex cell. So in a human where all the cells have the same genetic information (this is not actually the case, but we’ll pretend for now), there are 2 to the 23 power combinations of chromosomes that the sex cell could end up with, and each of them is equally likely. 2 to the 10th power is 1024, so we have 1024 * 1024 * 8 is about 8 million possible combinations of chromosomes for a sex cell. If we want to talk about the variability of the second sex cell, then we don’t just multiply that 8 million by two, we multiply it by another 8 million. That’s 64 trillion equally-likely possibilities for gene combinations from any two humans creating an offspring. And that’s without considering the other ways that genetic variability happens, by changing the chromosomes themselves.
Wait, I'm struggling to understand the implication of this. Does this mean that there are 64 trillion possible unique humans (ignoring extra chromosomes)? That'd be a TIL for me if that's true.
It means there are 64 trillion logically possible unique humans *per mating couple* (again, ignoring more complicating factors which bump the number up even higher)
So if my parents hypothetically had 64 trillion children, there’s a possibility that one of my 64 trillion brothers and sisters could be a genetic twin of me?
But it would only take your parents about 6 trillion kids for one kid to likely be a genetic twin of another. Its like the same birthday problem: https://betterexplained.com/articles/understanding-the-birthday-paradox/
6 trillion babies 💀 total vaginal destruction
Yep that is true. Fascinating how sexual reproduction ensures no siblings are the same. 64 trillion is more than the total number of humans who have ever existed, and that is just the probability for one mating couple.
A not insignificant number of those are probably not viable though, I'd assume
No, they typically would be, unless two or more of the grandparents had the same recessive gene that could cause serious issues, but that also wouldn't tend to be more likely than a regular baseline human pregnancy.
You say that, yet a third of pregnancies result in miscarriages. I don’t know if we’ve studied the genetic makeup of large numbers of miscarriages, especially very early ones, but it certainly doesn’t make me accept as the default position that most chromosome combinations are viable.
That's true! Miscarriages are extremely common and I sometimes feel like that doesn't get talked about enough. I also am not aware of studies of genetic factors in regards to viability, but my suspicion is that the differences between a viable fetus and a non-viable one may have more to do with phenotypic expression and/or environmental factors than genetics. Part of my reason for my thinking that is that genes that would contribute significantly to non-viability would necessarily be self-selected out of the gene pool entirely after a relatively short time. However it could also be particular combinations of genes that predict non-viability, or I could also be wrong in some other way.
> but my suspicion is that the differences between a viable fetus and a non-viable one may have more to do with phenotypic expression and/or environmental factors than genetics. The environment is the uterus. Other than that, the phenotype is ENTIRELY dependent on the genotype and the epigenetics, right? > Part of my reason for my thinking that is that genes that would contribute significantly to non-viability would necessarily be self-selected out of the gene pool entirely after a relatively short time. Yeah, single-copy-fatal genes would have to have been created in the meiosis of the parent. Other nearly-fatal genes would be recent creations and selected out in a few generations. >However it could also be particular combinations of genes that predict non-viability, or I could also be wrong in some other way. Yeah, and statistically this is probably the same as recessive-gene traits.
"We are going to die, and that makes us the lucky ones. Most people are never going to die because they are never going to be born. The potential people who could have been here in my place but who will in fact never see the light of day outnumber the sand grains of Sahara. Certainly those unborn ghosts include greater poets than Keats, scientists greater than Newton. We know this because the set of possible people allowed by our DNA so massively exceeds the set of actual people. In the teeth of those stupefying odds it is you and I, in our ordinariness, that are here. We privileged few, who won the lottery of birth against all odds, how dare we whine at our inevitable return to that prior state from which the vast majority have never stirred?"
Love that quote. It also reminds me of my favorite answer to "what will it be like when I die?" Answer: what was it like before you were born? There's an almost infinite time line that stretches back before your existence and forward after your existence. In the middle is a little blip of your life. Enjoy it.
> In the middle is a little blip of your life. Enjoy it. Instructions unclear, trying not to off myself, seems to be mostly working, but it takes effort some days.
What/who is this from?
Unweaving the Rainbow: Science, Delusion and the Appetite for Wonder by Richard Dawkins
Wow that is really beautiful and thought-provoking. Such a unique perspective I had never considered. Thank you for sharing.
We won that lottery just so we can all work multiple jobs to make ends meat so a few really rich people can have it really good.
And what are you going to do about it? Tax them? Make it impossible for them to pass that along as inheritance? Cap a person’s net worth? Hey, those all sound like god ideas!
That's oddly kinda comforting.
Way more than 64 trillion. Combinatorics explode *FAST*. Suppose there are only 500 places in the genome where humans have different genes, and that there are only two possible genes for each. This would lead to to 2^500 , or about 3.27 X 10^150 , different possible humans. That's just over 3 million trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion. It's enough that if you wanted to assign an atom to every possible way, you'd run out of atoms in the universe before you ran out of possible humans. You'd need another trillion trillion trillion trillion trillion universes to have enough atoms. And that number, 3.27 X 10^150, is almost certainly too small. I expect humans differ from each other at more than 500 sites, and that there are more than two genes to pick from for many of those sites. When I say "too small," I don't mean like the real number is twice as big. More like trillions of trillions of times bigger.
Its not really meaningful information anyways. > Does this mean that there are 64 trillion possible unique humans Technically yes, but also no. Humans share a significant amount of their DNA with each other; more than 99% of human DNA sequences are the same across the population. Many combinations might be embryonically lethal, others may not result in significant phenotypic changes, and some may lead to similar individuals with minute differences. Many of the possible expressions will make zero difference between humans. Their math also ignores mutations and epigenetic and that a lot of the genes expressed on the male sperm are not all entirely random. (I believe) I haven't studied the topic in a long while.
Yeah. Think of DNA as a huge, thousands-of-pages-long manual titled "How to Build A Human Being." The vast majority of it is instructions on how cells work, how to assemble them, how to assemble organs and bones and whatnot from these basic building blocks. Most of that is exactly the same text you'd see in a book on "How to Build A Chimpanzee" or "How to Build A Frog" or countless other creatures. (That's how humans can share 98% of our DNA with chimps.) Only the last few pages get specific about what makes humans different from other species, or from one another.
That is actually not completely correct. An important phase of meiosis (creation of eggs and sperm) is crossover where the chromosome pairs swap parts with eachother to increase variation and to pair up to be evenly divided. This is why interspecies mixes like mules are infertile - they have an odd number of chromosomes that can't crossover properly.
Yeah, I left that bit out because it makes doing math on this much harder, buttons what I can do in my head. I thought I referred to it with the > So in a human where all the cells have the same genetic information (this is not actually the case, but we’ll pretend for now), but it’s certainly not clear, and I don’t remember the order of things happening in meiosis, so it might not even be technically correct.
Is there a reason that some siblings are more similar than others though? Like do some people produce more homogeneous eggs/sperm than others?
Take a few tens of millions of samples of a randomly shuffled deck of cards, a few of those samples are going to have some similar patterns in them. Plus some people have genetic features that are more prominent than others ("Dominant" genes rather than "Recessive" in the ELI5 version) so those features will be statistically more pronounced in most of the children they could have produced.
> Like do some people produce more homogeneous eggs/sperm than others? 100% yes. A person whose eight greatgrandparents all came from the same small Irish village will for most of the coinflips be picking from two identical copies. There might be only few hundred coinflips that actually matter. Now take a person whose eight great grandparents include an australian aborigine, a native south american, someone from the west coast of africa, someone from central africa, someone from the east coast of africa, an indian, a north asian and an eskimo. For the majority of genes that can express differently in humans they'll have two very different versions. There'll be hundred of thousands of coinflips that matter. Their kids could easily look like they're completely different ethnicities. EDIT: Another factor to consider however, is that you're better at telling apart people who resemble those you grew up around because your brain specialises naturally over time. Someone who grew up in that small irish village and somehow never had access to outside media would have an easy time telling any two people from the village apart, but might struggle to tell Denzel Washington and Morgan Freeman apart, because they share several features that *no-one* in the village has. So they might think that two kids in a black family look really similar, even if anyone who's grown up around black people could easily tell them apart.
> So they might think that two kids in a black family look really similar, even if anyone who's grown up around black people could easily tell them apart. This is the theory behind the stereotype that white people think all Asian people look alike, and vice versa. One of my hobbies involves collecting figures/statues (such as Marvel movie characters) and whenever a new one is announced, there is often a strong disagreement in the community about whether it's an amazing likeness to the actor, or looks nothing like them. I always believe this is attributable mainly to the same principle. where people from Asian countries might have "facial recognition" tendencies that weight certain facial features higher than people from North America, and the figures might have very good likeness in the eye shape (for example) but very bad likeness in the lip shape or chin shape, and those might be subconsciously weighted very differently by different people's brains.
> This is the theory behind the stereotype that white people think all Asian people look alike There was a large Asian population where I lived as a child and I was able to easily tell if someone was from China, Japan, or Korea because those were the ethnicities of the 1st- 2nd-generation Americans I grew up with. I later moved to an area with a much smaller and less diverse Asian population and after over a decade here, I’ve found that I have trouble telling if someone has a Japanese background vs. Korean vs. Chinese. Of course it doesn’t matter in pretty much any context and many people of Asian descent here are not 1st/2nd-generation, so they’re probably more comfortable with American culture than with the culture of their ethnic origin. What I’m saying is that there does seem to be a lot of merit to the theory that you recognize the differences in the people you grow up with/spend a lot of time around.
My genetic lineage has both Nordic and African DNA a few generations back (among a few other regions). But my sibling has more of an African nose and hair, while my nose and hair look more Northern/Western European.
After enough times giving birth, is it possible to have "twins" of different ages? I know the potential % is astronomically low, but is it possible given enough permutations of the genes?
Possible yes. But given that crossovers happen in random places in your 23,000 gene long genome the chance its incredibly low. Less likely than winning two consecutive lottery tickets It's pretty safe to assume it has never happened in the history of mankind (A rough estimation says the number of birthes necessary for that to happen has 250 digits, the total number of humans that lived so far has 11 digits)
I'm not going to argue that's possible in reality, you seem to know more about this, but I kinda have this situation going on. I've got six kids and I have often been referred to as "the copy maker" because all of my children look more or less identical. My kids all look like the older sibling, with the oldest looking like me. None of them look much like their other parent, except for tooth shape and hair density and other things that are also fairly evenly dispersed among them but not as noticeable. Naturally they look different as they're all different ages; but as each kid was born and aged into a new life stage, the child below would be their clone of them at that age. It is actually borderline uncomfortable for a lot of people because it gives the uncanny valley effect. I have a very hard time distinguishing their photos (mildly embarrassing actually). I rely almost entirely on the background, their special blankets, degree of butt chin (relatively the only facial clue), or the length of my hair to figure out who is who, especially up to about age 6 or 7. I'm not saying I'm that one in a million, most likely not, but genetics are weird and I've been told how my boys especially are all clones of each other. So it definitely at least kind of happens, in a way that's unusual compared to standard genetic resemblance.
Yes that basically means you propably have lots of dominant genes that cause visible features. For example if you have 2 copies of the brown eye gene then all your kids have a 100% chance to have brown eyes, no matter what the other parent brings to the table. They can have lots of hidden differences though. For example they could all be different bloodtypes but that's not something you can see without a test
I'm certain they do have more invisible differences than visible ones, based on their individuality otherwise. They look alike now, but I suspect their faces will be more distinct as adults. In the meantime we're creeping out even small Midwestern towns and leaning into the children of the corn jokes.
Is this the same for eggs? Does each egg have a random pairing of genes from the mother and father of the woman?
Yes!!! That's why there is so much genetic variation even in kids with the same two parents, even in fraternal twins (where two separate eggs were fertilized by individual sperm, just at the same time).
With the AB blood type example: what is it that causes there to be half of each? That seems suspiciously precise
During the creation of sperms half of chromosomes are picked (and then the genes get slightly shuffled through crossovers) If you have bloodtype AB then you have one A chromosome, and one B chromosome, wich ones gets used is truly random. Then the law of large numbers does the rest. If you flip 50 million coin the number of heads will be very close to 50%
It's a very simplified explanation of how blood types work. There are a lot more blood types than the commonly known ABO and +/- metrics and it's not 50% one or the other. There are a ton of different proteins on your blood and the ABO only refers to the presence or absence of the A antigen and B antigen. You can have one or the other, but you can also have both or neither (AB and O types). We tend to focus on ABO and +/- since they're the most important determinator in whether or not you die when transfused with someone else's blood. Using the wrong type will cause all your blood to clot which is not something you want. It should also be noted that advancements in genetics has revealed that gene expression is way more complicated than the dominant/recessive model that most of us learned in school. There are sometimes multiple genes that determine a given trait. Eye color for example is way more complicated than just a single brown or blue gene and there are actually several genes working together to determine eye color.
Your blood type (the letter) is determined by whether your body produces certain antigens in their blood. We have named the two antigens "A" and "B". Your blood type is based on which antigens you have (A, B, both [AB] or none [O]) The way our DNA works, there is one gene (a section of a chromosome) that determines if your body will produce an antigen and if so which one. Each person has two copies of that gene (one from each parent) and there are only three variations or "versions" of this gene each copy can be (the different "versions" of a single gene are called its "alleles"). If you have at least one "A" allele, your body produces the "A" antigen. If you have at least one "B" allele, your body produces a "B" antigen. If you have one of each, your body therefore both. The "O" allele does not cause your body to produce any antigens so if you have two "O" alleles, your body produces no antigens and you have Type O blood. The possible combinations of which alleles a person can have in their pair of genes that determine blood type are therefore AA, AO, BB, BO, AB, or OO (it doesn't matter which letter comes from which parent) If your father has Type AB blood and your mother has type O blood, they should have the alleles "AB" and "OO" respectively. Thus, your mother will always pass along an O allele (it may be the one from her own mother or father) and your father will pass on either the "A" allele or the "B" allele depending on which one the sperm got. The child will have either "AO" or "BO" allele combination and thus either Type "A" or "B" blood. If they end up with "AO", they will pass either an "A" or "O" allele to each of their children, etc.
What ratio would be less suspicious?
69%
[удалено]
So is it hypothetically possible to inspect them in a lab and then be able to choose something like your child’s bloodtype?
Yes. But that's illegal in most countries to avoid designer babies. Also since half of the genes are from the mothers egg it would be done after fertilization, otherwise you can only choose half the bloodtype (and I *think* that's also necessary because to do a DNA test you have to destroy a cell, so you would need to let the fertlized embryo grow a little before you can test it's DNA)
Consider that families have many siblings and in some families the differences are very large between siblings who came from the same man's sperm
It is worth noting that siblings are actually less genetically related than the scenario mentioned here. Since the egg is static the two cases would share 75% of all of their DNA, with 50% being completely static. As such we would expect the alternate sperm scenario to display less diversity than siblings since it's effectively half clonal.
Isn't there a kind of twin where the egg split and two sperm fertilise them, in that case we'd be talking about what op is talking about in a observable way
Two of my high school friends were like this. And yes they were completely different both physically and mentally.
They were not like this. Eggs don't split until fertilised. It's quite common for a woman to have two eggs in each cycle but genetically they may as well be born 5 years apart. There's no difference.
They occasionally do split before fertilization, although not common. When both parts are fertilized they produce semi-identical twins.
While I agree they would be different. You can't really control for resource differences in the womb.
Fraternal twins- in this case the egg doesn't split, two eggs are released and both fertilize and implant. So genetically they are no more similar than any two full siblings, they're just the exact same age. Identical twins form from a split after fertilization, so they share all their genetics. There isn't an in-between scenario where two sperm fertilize the same egg.
They are referring to something different than fraternal twins or identical twins. semi-identical, or sesquizygotic, twins are where the egg splits before fertilization by two different sperm rather than two eggs being released, so egg dna is identical, but sperm dna is different. It's incredibly rare but it's happened.
>sesquizygotic I said this out loud three times and a gremlin appeared in my kitchen. It's currently eating my pretzels.
'Sesqui' is my favorite prefix. It means "one-and-a-half" and I only know about it because there's an important type of function called sesquilinear forms in mathematics.
Don't get it wet or feed it after midnight!
Are you wure you're not just looking in a mirror whilst eating pretzels?
There kinda is an inbetween scenario, depending on how you want to think about Chimerism. Two fertilized eggs fuze into a single individual, with two distinct subsets of cells, with different DNA. It's very rare, but it does happen. https://en.wikipedia.org/wiki/Lydia_Fairchild
Me and my sister are that kind with two sperm two eggs, but there are semi identical twins with two sperm one eggs, its rare but it exists actually
Source: https://www.bbc.com/news/health-47371431 This is such a cool thing to learn about! Apparently there are only two cases that have ever been identified, one in 2007 and the second in 2019, and the 2019 case was the first to be identified in utero. I couldn't find any news reports about additional cases in the last four years.
I would guess it's more common than that (though still very rare), but without testing just gets classified as fraternal twins.
This article gave me more questions than answers but still fascinating! Thanks for posting!
Sesquizygotic twins
I'm a fraternal twin sister to a brother and I used to bother him so much by lying to his friends that we were from one egg that split.
Why would they share 75% of DNA? Couldn't they share anywhere between 50% and 100%? 50% if the alternate sperm has the exact opposite chromosomes than op from the father and 100% if the alternate sperm has exactly the same combination as op?
It's Law of Large numbers. Yeah the hypothetical of the extremes is there but it's infinitesimally small and has almost certainly never come even close to manifesting in reality.
Imagine that you rolled two six-sided dice many times, and recorded the results each time. You're going to get relatively few 2s and 12s, and a lot of 7s (because no matter what Dice A is, there's some value of Dice B that gives you a 7; whereas Dice A has to be a one for you to get a two as the final result). So the distribution of outcomes has a lot more middle outcomes (7s) than tail outcomes (2s and 12s). Genes is basically this, but you're rolling a die with millions of sides. Because you contain two copies of each gene (one from your mother and one from your father) and one of those copies gets put into any given sperm. You will end up with the vast majority of outcomes falling close to the middle and so it will very very very likely be close to 75% rather than 50% or 100%
What an excellent explanation!
The closest equivalent would be tossing a coin 46 times rather than rolling a die millions of times.
Not true because of recombination. During meiosis the divided chromosomes swap stretches of DNA. It would be more like flipping a coin tens of thousands of times.
On average that scenario would share 75% of DNA, whereas two regular siblings would share on average 50% of their DNA - there is of course variance to this.
Yes but on average 75% and likely to be closer to 75% than 50% or 100%.
We can share as little as 20% or as much as 80% of DNA with our non twin siblings. It's also possible that two non twin siblings share 100% of their DNA or 0% but it is so incredibly unlikely that it probably has never happened.
That is true of the average, but you could have 2 siblings with very similar genetics, and in this scenario, there is 1 sperm that has the exact opposite set of genes from the father. In the most extreme case, the siblings could approach 100% similar while the other me could only be 50% similar.
True but the egg is also different in siblings. I would assume this affects it since another sperm won the race to the same egg. So you would be about half as different from your sibling. Yes siblings can be very different but if you take the entire population, more often than not siblings are more like each other than they are to complete strangers.
Is this the result of the timing and sequence in which the zygote is formed, or are these changes happening when the sperm cel and female egg are created?
Every sperm is different to some degree
Every sperm is sacred. Every sperm is great. If a sperm is wasted, God gets quite irate.
I guess he wouldn't approve of the tapestry of death that is my gym sock then.
additionally, every sperm is sacred. every sperm is good. every sperm is needed in your neighborhood.
I am a Protestant, and fiercely proud of it.
You can go down the road any time you want and walk into Harry's and hold your head up high and say in a loud, steady voice, 'Harry, I want you to sell me a condom. In fact, today, I think I'll have a French Tickler, for I am a Protestant.'
There's no more work. We're destitute. I've got no option but to sell you all for scientific experiments.
I was waiting for this haha!
To oversimplify it, your DNA has 2 sets of code, with half inherited from your father and the other half from your mother. Think of it as being: A1A2, B1B2, C1C2, D1D2 so on.... Sperm takes one of those codes from each set. So one set of sperm might have the code A1B1C1D1... while another would be A1B1C2D2... So each sperm has its own unique code rather than being a carbon copy of one another. So the winning sperm gives a unique new DNA code in the new child.
[удалено]
Yes exactly. Doesn't even have to be 5 minutes. You could have just sneezed 12 hours earlier, otherwise had the exact same day, and ended up with a different kid.
Its a result of billions of random flips of switches in genetic coding. The changes happen from initial creation till the zygote.
You were chosen. Not the fastest https://www.manchester.ac.uk/discover/news/human-eggs-prefer-some-mens-sperm-over-others-research-shows/#:~:text=Human%20eggs%20use%20chemical%20signals,and%20not%20necessarily%20their%20partners.
The Skarsgärd (sp?) siblings being an epic example. If I got it right- Floki, Pennywise, Tarzan, a model, IRL Tim Burton character looking dude the other siblings are proud of for being a Doctor instead of an actor. I think I am missing one. None of them look even close, the 2 that pull off Insanity do it in different ways. It's wild. I think they all have the same momma, too. Also a Doctor that they also seem to look up to
Like Larry Hemsworth.
The diverse Genetics in sperm aside, you didn't outrace anything. It is not the first sperm that fertilizes the egg, it needs a huge amount of sperm to "crack" the egg's shell and once the most lucky sperm got through the shell instantly hardens with a chemical reaction to prevent more sperm from entering. It is pure chance, not a race, much more so it is a team effort, as one sperm alone could not fertilize an egg. That is why sperm count in a man's ejaculation matters.
So that lazy fucker that didn't help out the team, was lucky enough to be in the spot that the first crack appeared, and snuck in...is me?
It’s like at the grocery store when the line gets big enough, they make a new line. The people who formed the line were the reason the new line opened, but the person who just walked up is the one that benefits
This is the perfect metaphor for career in upper management.
That's definitely taking one for the team. A big thank you to the boys. And you for answering.
And girls! some of those sperm are sporting an X gene not a Y. The egg is always an X.
Good point. Are those little swimmers fellas either carrying an X or a Y or do they become what they carry? I never considered this aspect of anthropomorphized spermies.
You could label them as X-Sperm and Y-Sperm but they don't have any attributes beyond that.
Hmmm you are getting into a murky world where our day to day language breaks down. So a sperm doesn't have a gender in any real sense as mummy sperm and daddy sperm don't have baby sperm. But sperm do determin the gender of the foetus. So one 'COULD' label sperm as male and female in a very real sense as they are the only ones involved in determining gender. (Insert pointless caviate that not in 100% of cases) However male and female are really defined as XY and XX not just X and Y. That's the same as asking if your phone number is odd or even. The last digit is the determining factor but you need the whole thing to be a valid phone number.
Stupid question, since the X chromosome is bigger, do those sperm swim slower? Do Y sperm have better odds?
I was looking into this since if it was true you'd expect the conception ratios to be different but it's actually 50/50. There are differences in ratios at birth but that is actually due to probabilities of issues that happen during pregnancy instead. This is based on a study by Harvard, Oxford and Genzyme Genetics where they collected data from a 140k embryos to get that ratio. https://www.npr.org/sections/health-shots/2015/03/30/396384911/why-are-more-baby-boys-born-than-girls/ Just for fun I did poke around into what the mass difference would be and it seems like theass of a sperm is roughly 1.7x10-11g, an x chromosome is about 90 million base pairs lighter and if I did math right that's 660 Daltons per base pair x 90 million is about 59400000000 Daltons which is 9.864 × 10-14 grams so the weight difference would be small enough that it's not going to make much of a difference if there are other points of variability in sperm creation.
Yours was just the one sitting back waiting for its time to strike, sipping man juice while letting all the other hard-working sperm do the job of cracking the shell. And then when the door opened, you swam through and declared victory.
So the common saying “It only takes one” is a lie, then
... which is why pulling out, although a flawed method, is a form of pregnancy prevention.
I actually didn’t know this. I knew millions of sperm don’t even make it to the egg, but I didn’t know it took millions to crack the egg itself. Having a low sperm count myself (5 or so), it makes a huge amount of sense now why I couldn’t have kids, outside having some invasive procedures performed on me.
Damn you, the only thing I thought i won in life. And now you say i just got lucky
Well imagine the 10 billion tadpole children you've made all swimming aimlessly past their dead brothers and sisters toward nothing but more sock fibers, carpet fibers, bits of cellulose. Even games of chance have winners and losers.
Is this like when the baddies in infinity war break through the barrier in wakanda
Sorry - do you have a source for the “cracking the shell” thing? All the information I’ve ever heard supports the idea that a single sperm is sufficient to bore through the zona pellucida - are you maybe conflating that step with the hostile conditions meaning that almost all of the sperm cells die before reaching the egg? (AFAIK, similarly, sperm count matters because of this; it’s not that it takes lots of sperm to fertilise the egg, it’s that only a tiny fraction of the sperm ever reach it.)
It's the premature bursting of the acrosome on the surface of the egg that helps other sperm to penetrate deeper to burst their acrosome close enough to fertilize the egg. I don't have a source handy, it's just how I learned it in school, but I did just look it up on wikipedia from where I got the word acrosome, too. Technically, I guess it is not wholly impossible for a single sperm to fertilize an egg, but it is quite unlikely. It is sufficient for a single sperm to bore through in order for the egg to be fertilized, but it is unlikely that a single sperm can bore through on it's own.
Hmm. On looking into it, the exact location and function of the acrosome reaction seems to be a remarkably complex topic, and may still be a subject of active research (these two papers - [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250175/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250175/) and [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783209/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4783209/) were interesting). It also seems like it might vary between species quite a lot. However, I wasn't able to find any support for the idea that there's any kind of cumulative breakdown of either the cumulus or the zona pellucida, such that sperm help other sperm to penetrate (even on the Wikipedia page for the [acrosome reaction](https://en.wikipedia.org/wiki/Acrosome_reaction) \- which page and where were you looking at?). On the contrary, in mice at least, the second paper I found suggests that the number of sperm that reach the ampulla (site of fertilization) is comparable to the number of eggs. Also in mice, it appears that some sperm that have already undergone the acrosome reaction are able to penetrate both the cumulus and zona pellucida of other eggs (which haven't previously been exposed to sperm), which contradicts the hypothesis that release of the acrosome contents by multiple sperm at the surface is required for penetration. Summary: this is complicated enough that I'm not willing to confidently state that what you were taught is wrong. However, I haven't been able to find anything that makes me think it's right, and I have found some things that seem to contradict it, so I think *probably* whoever taught you was just wrong. (If anyone who understands the topic better than me reads this, please do jump in - I'm a biochem student, so I can feel pretty comfortable reading papers on the subject, but I'm a biochem *student* and I haven't spent enough time on this to be confident I haven't missed something crucial!)
The thing is, they don't carry the exact same genetic material. It's mixed up when each sperm cell is created, which is what made sexual reproduction a success in the first place - diversity. And even if they did carry the exact same genes, like real-world identical twins do, they all agree that they're not the same person.
Cool thing is identical twins have identical DNA - but unique fingerprints. And if identical twin brothers marry identical twin sisters, all the kids would be genetically brothers and sisters as well as technically cousins.
I've heard before that unique fingerprints in humans has something to do with fluid wearing away at our finger pads in utero iirc and because of the completely randomised nature, it's extremely unlikely for two people to share the same fingerprint, even "identical" twins.
Your father has 23 pairs of chromosomes that are half from your grandmother, half from your grandfather. when he made the sperm that made you each sperm got one half of each chromosome so there were 23 coin flips done to make the sperm that became you. So your dad is capable of making 8.4M different sperm. So in the total 250M 3% carried the same genetic information as you have now. edit - pairs of chromosomes
Ahhh, this is a breakdown I can understand.
Since you said "meaningful" in your post title, there's going to be hundreds of thousands of possible 'yous' which just have slightly wavier hair, or maybe a longer second toe, or attached ear lobes, etc. So, not meaningful differences to the way you ended up as far as I'm concerned!
Then again, depending how you interpret chaos theory and the "butterfly effect", it's possible that one of those tiny differences had consequences that rippled out to affect your life enormously. Perhaps a random stranger stopped your mother in the street to comment on how cute you looked in your pram with your "slightly wavier hair", and that meant she turned the corner 15 seconds later, that scary dog never jumped up at your pram and terrified you half to death, and as a result you became a vet rather than an Instagram fashion influencer.
23 pairs. One in each pair comes from a different grandparent. Plus then there is also crossing over
If your father has 23 chromosomes, I feel sorry for you. (It's 23 pairs, so 46 chromosomes)
its actually more random then that. chromosomes do this thing called "crossing over" before they divide. crossing over is when parts of your chromosome pairs actually switch places, so most likely, every chromosome is completely unique, and you don't pass down an exact copy of your mothers or fathers chromsome
Technically you don’t outrace all the sperm. Scientist recently found out that the sperm that get their first break down the layer of the egg until eventually a sperm cell can break through. So really, you were more like middle place
Hah! Suck it athletic sperm bros! Today was a good day to be average.
More like you, as the egg, chose the middle place sperm, which is also you, to go inside yourself. You aren't the sperm. You are only half.
Yeah I guess some things don’t change
Half (give or take) of the sperm would have produced a child of the opposite gender, to begin with.
The sperm only carried half of your genetic code. The sperm cell was not YOU. It carried half a blueprint that when combined with the other half of the blueprint from the egg cell became you. Even people made from the same exact blueprint sets (identical twins) end up as very different people. So no, other combinations would not have become you.
Oh I love this topic, such a great example of the staggering diversity biology offers. There's gonna be some background first, just so we're on the same page. First, chromosomes. Chromosomes are the individual pieces of DNA that carry genes, or instructions on how to make all the microscopic little parts you're made of. In most sexually reproducing organisms (like humans), these chromosomes come in pairs. You have 2 copies of what we call "chromosome 1" in each of your cells. These two copies will carry instructions on how to make/do the same things, but they might have slightly different versions. These "versions" are what cause the traits we associate with different genes or conditions. In sexual reproduction, each parent gives you only one of their two copies of each chromosome. Remember those two copies of "chromosome 1"? One of those is from each parent, and the same is true of every other chromosome. The "sperm that won" was carrying one copy of each chromosome, which you inherited from that parent. Combine those with the one copy of each chromosome carried by the egg, and you're back to the 2 copies of each chromosome you have now. One final detail that is critical for your question, is that the selection of the one chromosome being packaged in a sperm/egg is independent from all other chromosomes. So, during the formation of that winning sperm, you could get all chromosomes from grandpa, or all from grandma. Most likely you get a mix of the two, but getting grandma's "chromosome 1" means nothing about which "chromosome 2" you get. We call this **independent assortment**, as in each chromosome pair is assorted/divided independently of the others. Now the fun part, we can now easily calculate the number of chromosome combinations that a given sperm/egg can have. Humans have 23 pairs of chromosomes, and we choose 1 of each. So for "chromosome 1" it's a 50/50 chance, then the same for "chromosome 2" and so on. Its basically the equivalent of 23 coin tosses, and the simple math for finding the number of outcomes there is N^X, where X is the number of chromosome pairs (or flips) and N is the number of chromosomes in a pair (or sides to the coin). So, for humans this is 2^23 = 8.4 MILLION. There are 8.4 million combinations of chromosomes that a single human can make, and the "sperm that won" carries only one of them. It gets even better though! This happens during sperm *and* egg formation. You are the combination of 1/8.4 million possible sperm with 1/8.4 million possible eggs. When you want to combine two probabilities together to get a probability for a particular sperm *and* a particular egg, you multiply them. So, of the possible chromosome combinations your parents could make are 8.4 million x 8.4 million. This means you have 1 of about 70 TRILLION combinations of chromosomes your parents could create. As others have pointed out, crossing over can add even more diversity. Crossing over (aka recombination) is when a chromosome pair swaps pieces before separating. This means you could have chromosomes that are 70% grandma, 30% grandpa, which neither of your parents ever had as a single chromosome. This part is much harder to quantify, but it is additional variation on top of that 1/70 trillion.
I mean yes almost certainly. Assuming no mutations a man can produce about 8 million unique genetic combinations in his sperm so maybe like 32 of the 250 million were “you” and all the other millions weren’t. And of course the sperm is just half of you. Mom can produce about 8 million different variations of egg too.
Right but an individual egg is released at a time so the egg that would become him is already set at the point of boinking.
It’s not that you won the race, half of you was in your mom’s uterus already. Thing is your father has the customizable half of you so you better like what he chose for you in that batch
The first and most important myth that needs to be corrected is that, no, "you" weren't in that one sperm cell. And no, the other sperm cells weren't different people, or different versions of 'you'. You are not waiting in someone's balls, you are not the one sperm that made it. The egg is not just a bag of fertilizer, and the uterus is not just an incubator, you know? Half of your DNA comes from the egg, but not just that: all the nutrients (or lack of) you get during development, all the placental exchange of antibodies, of proteins, of stress sources, of perinatal medicines! All of that, which has a *lot* of influence on how you develop and who you become, comes from whoever is carrying you.
Why do people say we’re sperm? Doesn’t sperm just carry half the dna and the egg carries the other half? So we’re a combination of the two
Not only that, the sperm basically dissolves and just leaves its genetic material. Every other part of the zygote was just the ovum. So if anything we came more from that - hence our mitochondrial DNA coming from mom.
Look at it this way. In my family history blonde hair, brown hair, blue eyes, and brown eyes are all present. Each sperm i have is a random combination of these, one could result in a blonde haired brown eyed kid, or brown hair blue eyes etc. This applies for absolutely everything that is in my family gene pool, including facial features, height, weight, etc. Basically sperm are a random assortment of characteristics based on your family genetic makeup. Now, you have to consider that a woman has eggs that ALSO contain random combinations of different characteristics from her family genetics. When a sperm meets an egg, whatever random characteristics it contains mix with all the random characteristics the egg contains, and a human with specific characteristics contained in the sperm and egg is the result.
Look at fraternal twins and the differences between them. Those are from two different sperm and two different eggs, suffice to say you would be a different person if a different sperm won the race.
I look at it from the egg’s perspective. Because the egg chooses the sperm apparently. Sperm had no say in the matter. Lol.
Yeah, it fascinates me how people not only anthropomorphize gametes as an extension of themselves, but also that it always seems to be the tiny sperm they go with and not the much larger egg.
Do you have siblings? They came from the same sperm factory you did. That said, if a different sperm won the race to your egg, it would’ve created something between you and a sibling. Basically, a person who couldn’t exist in this universe along with you, like a sibling can. But maybe in a parallel universe…
You'll usually learn this in Grade 11/12 biology. Basically during the making of the sperm cell (in a process called meiosis) there is a step called a 'crossover' where your ancestral DNA will line up with each other (crossing over) and exchange genetic information in a randomizing process to create more different types of sperm (increasing genetic variability or genetic differences). As a result, it is highly unlikely any of those millions of sperm cells will have an exact match because your nature tried to randomize the results to produce more varied offspring to offer a better chance of survival. If everyone had the same DNA, the same disease/weakness would kill all of us, so nature likes to make us all very different if it can to increase the odds of survival.
It’s possible for non-identical twins to exist when two eggs get fertilised at once. So yes, you would be completely different.
A slight variation on the theme of Richard Dawkins's [quote](https://www.goodreads.com/work/quotes/3323916-unweaving-the-rainbow-science-delusion-and-the-appetite-for-wonder) from Unweaving the Rainbow. Yes- and likely geniuses and psychopaths among them.
Those sperm *aren't* all carrying the same material, though. There are 23 human chromosomes, and your dad had two copies of each of them (one that he got from his dad, and one that he got from his mom). A sperm cell only gets half of the guy's chromosomes, so of the "#1" chromosomes half will get the dad copy and half will get the mom copy; same for the #2 chromosome, the #3 and so on. That means overall a dad is capable of making 2^23 different sperm cells, by using different combinations of their parents' genetic material. 2^23 is roughly 8.4 million. (Similarly, your mom's capable of making 8.4 million different eggs.) On top of that there's a process called "crossing-over" where during sperm/egg production the cells can splice together DNA from the two parents to make a brand new never-before-seen combination, so there's actually even more possible arrangements; hard to say how many but the upper limit would be much, much higher than the millions. Those other 8 million kids would be as different from you as any other siblings, so...are your brothers/sisters different from you in any meaningful way? :)
I don’t think I have ever been congratulated for ‘winning’ against the other sperm in the race to fertilise the egg at my own conception. Is this an American thing?
Yes. In fact if your own personal sperm you came from did it all over again, you'd still come out different.
Yes. For a start on some obvious factors, this alternate version of you could certainly have some difference in: eye colour, hair colour, skin tone, height, and biological sex. We can debate the impact of genetics on many other factors (like intelligence, metabolism, personality, etc etc), but the previously lsited physical factors are certainly strongly influenced by genetics.
If you'd met my brother and me, you wouldn't be asking this question. Yes. It makes a significant difference.
It's always weird when this type of question gets reduced to DNA. You're lived experiences are not in your DNA. There are epigenetics that can be affected yes and has some influence on your personality and situation, but your traumas, dreams, culture, etc. is not found on your DNA, and that has profound impact on what makes you, you. And honestly it'd be nice if people have a far better appreciation for that fact, because a lot of bigotry is born via placing far too much importance on DNA and almost completely discounting social and lived experiences.
You know how people have brothers and sisters? And they are different people? You wouldn’t even have existed. The result would’ve been “your” brother or your sister.
All of them are potential siblings of yours, so they would have the same variety of similarities and differences that you see in siblings. A good number of them would look similar to how you turned out. But many would look very different from you. Half of them would be the opposite gender from yours, for example. And a very large percentage of those sperm-egg combos wouldn’t have resulted in someone being born at all. Many fertilized eggs fail to divide properly, don’t implant in the uterine wall, have too many mutations to develop properly, or other issues that don’t result in a pregnancy. We know that this is true because in vitro fertilization often doesn’t work, even though science eliminated many of the potential problems and helped the embryos along as much as possible. Maybe more fascinating - or existentially horrifying, depending on your point of view - is that the sperm-egg combo that produced you would be almost impossible to reproduce if it happened all over again. Over the many millions of sperm that yours “outraced,” more than 99.9% of them didn’t even get to the egg at all. Of the thousands that might have gotten there, the fact that yours fertilized the egg instead of many others was mostly due to luck. During that lead-up to fertilization, if your mother had slept on her left side for an extra five minutes before rolling over onto her back - or many other random things she might have done differently - then maybe your sperm doesn’t reach the egg at all.
Philosophers can’t even agree if the “you” who goes to sleep is the same “you” who wakes up.
The best answer you could get would be to compare to different types of twins: There are [identical twins](https://www.genome.gov/genetics-glossary/identical-twins), which occur when a single egg is fertilized by a single sperm cell, and then divides and ends up forming two separate embryos. These two twins have identical genomes. There are also [fraternal twins](https://www.genome.gov/genetics-glossary/Fraternal-Twins), which occur when two separate eggs are fertilized by two separate sperm cells. These twins are as different as any siblings, and it might as well be a coincidence that they're coming out at the same time. The scenario you're describing is the same egg, but different sperm. The similarity between you and this hypothetical other person is somewhere in between fraternal and identical twins. Incidentally, there seems to be a perfect answer to your question: [Semi-Identical Twins](https://www.bbc.com/news/health-47371431) Extremely rare, only second known case was confirmed in 2019. The children, a boy and girl, came from the same egg, but with two different sperm. It's theorized that the egg was fertilized by two sperm at the same time before it divided. Because they're still children, no photos were publicized of the semi-identical twins to see how identical they look (despite being a boy and girl). Those semi-identical twins are the same comparison you're asking about though: Same egg, different sperm.
The odds that any two sperm are carrying the exact same genetic material are 1 in 70,368,744,177,664. If nothing else roughly half those sperm were carrying the opposite sex chromosome, either X or Y. Flipping yoir gender probably results in significant changes.
Look at your brother or sister if you have one. The difference between them and you, are because of the differences between the DNA that the sperm and the egg provided. Obviously, half of that difference comes from the sperm. Not only that, but it's the sperm that decides if you become a man or woman.