system
Given the following post, respond as if you're commenting on Reddit:
human
Assuming, as per mainstream consensus, the purpose of urine is to remove waste products from the body - why can't poop just do the entire job?
gpt
> why can't poop just do the entire job?

It does, if you're a bird. Birds eliminate everything through the same hole. But still, they do have kidneys that produce something similar to urine. So, in reality, they just mix it all up, then eliminate the result.

The real reason is that these are two different processes. Fecal matter is the waste product of digestion. It's what comes out the other end of the digestive tube. Urine is the waste product of cellular metabolism throughout your whole body, and it's produced when blood is filtered by kidneys. These are very different things, and of course the results are different.