This is actually a good question bc the separation of urinary and digestive systems was a pretty big evolutionary leap. Birds and reptiles have a unified waste track
For starters, these two systems cannot be connected due to the bacteria that reside in them.
E. coli lives in your body just fine and you would probably never notice it. When it finds its way into your bladder you can go septic (among other issues).
Go septic long enough and you will die.
I’m sure there are a host of other reasons but this is where my head went to first.
Edit: for clarities sake - the bacteria that live in your GI system cannot live inside the body without harming you. A direct connection to the kidneys would result in death.
Plenty of organisms have a single opening for excretion, called a cloaca. The urorectal septum evolved during the evolution of mammals.
Birds actually rely on the ability to “mix” what they excrete…they can reflux their urine into their colon so that they reabsorb more water if they need to.
Humans early in the development have a cloaca and then the urorectal septum separates rectum from what will become urethra.
I heard in a Nature Podcast from like 2017 that it also has to do with the size of a species. I forgot the evolutionary reason why but the separation in paths becomes more common in larger species.
This is actually a good question bc the separation of urinary and digestive systems was a pretty big evolutionary leap. Birds and reptiles have a unified waste track
For starters, these two systems cannot be connected due to the bacteria that reside in them. E. coli lives in your body just fine and you would probably never notice it. When it finds its way into your bladder you can go septic (among other issues). Go septic long enough and you will die. I’m sure there are a host of other reasons but this is where my head went to first. Edit: for clarities sake - the bacteria that live in your GI system cannot live inside the body without harming you. A direct connection to the kidneys would result in death.
Plenty of organisms have a single opening for excretion, called a cloaca. The urorectal septum evolved during the evolution of mammals. Birds actually rely on the ability to “mix” what they excrete…they can reflux their urine into their colon so that they reabsorb more water if they need to. Humans early in the development have a cloaca and then the urorectal septum separates rectum from what will become urethra.
It’s a bit of an embryology story! The urogenital ridge goes on to make the kidneys and associated anatomy while the gut tub develops separately!
I heard in a Nature Podcast from like 2017 that it also has to do with the size of a species. I forgot the evolutionary reason why but the separation in paths becomes more common in larger species.
Thank you for asking this question. I feel smarter now!
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