system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If our bodies can heal cuts and open wounds, why can't we grow limbs back after being amputated?
gpt
Scientist's don't actually know. The prevailing theory is because of where the cells originate and the difference between stem cells and simply having cells divide.

When we are a fetus, growing inside the womb, our Stem Cells are being used to build everything. It is building bones and muscle and organs and skin. Stem Cells are blank discs that hold the information to do anything in the body.

After we are born, we no longer produce stem cells in such quantities. Instead our individual cells will divide. This is what causes skin to grow back over a cut. It is just the skin growing back.

Why does this happen? Scientists aren't sure. Figuring it out would help amputees regrow at least rudimentary body parts and even organs. Most studies on the topics look at reptile DNA since so many lizards have the ability to regrow tails and even appendages.