system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why can the liver regenerate itself but the rest of your organs can’t?

I was reading an article and it said the liver can be cut and transferred to another body and the liver will regrow in both people. Why can’t we do that with other organs and why can’t they fix themselves?
gpt
The cells of the liver are "programmed" (genetically) to do that. The cells in your, say, your heart, not as much. 

Why did the liver evolve this self-regenerative ability? Because, it's job is to process toxic junk in your body. It *has* to regenerate. 

Why doesn't everything in your body do that? 

1) your genes don't last forever. At the ends of your chromosomes are these things like called a telomere that caps it off. The telomeres shrink as they get copied to make new cells. Eventually, you run out of telomere space. And then you start losing critical genetic information. We think this may be what it means to get old, at least partly. You die. 

2) evolution isn't particularly "smart." It just happens. While it would be nice to evolve into immortal, regenerating beings, our species is still able to survive and reproduce without it, so we did. If there were some mechanism to regenerate infinitely, it's probably rare or costly or just "locked out" for our species. By "locked out" i mean that the branch of the evolutionary tree we happen to spring from already eliminated that ability for one reason or another, including random chance (mutation).