It is a know fact that very young babies can regrow the distal tips of fingers when cut off by accident. Human babies lose this ability after a few months into life.
Body parts regrow forever: the skin is redone every 30 days. The regrowth, though, is not a separate process from self-renewal from wear and tear. Bones, for instance, remake themselves to the last atom every 4 years, yet a broken bone won't regain its original shape in a human adult.
So the question is a matter of restoring a pattern. Why that doesn't happen is not understood. Some vertebrates can do it without much trouble--think salamanders being able to regrow part of their brain and eye, beyond the well-known limb and tail cases.
From an evolutionary perspective we can speculate that the formation of a scar is a big deal: it enhances short-term survival, which is a prerequisite for long-term survival (this is not something silly to say). Current medical research is showing (and already applying) that preventing scars allows some tissues to regrow normally, the nervous system included. Still a long way until medicine can regenerate a lost limb in a human, but there's supporting evidence towards its feasibility in the near future.
Body parts regrow forever: the skin is redone every 30 days. The regrowth, though, is not a separate process from self-renewal from wear and tear. Bones, for instance, remake themselves to the last atom every 4 years, yet a broken bone won't regain its original shape in a human adult.
So the question is a matter of restoring a pattern. Why that doesn't happen is not understood. Some vertebrates can do it without much trouble--think salamanders being able to regrow part of their brain and eye, beyond the well-known limb and tail cases.
From an evolutionary perspective we can speculate that the formation of a scar is a big deal: it enhances short-term survival, which is a prerequisite for long-term survival (this is not something silly to say). Current medical research is showing (and already applying) that preventing scars allows some tissues to regrow normally, the nervous system included. Still a long way until medicine can regenerate a lost limb in a human, but there's supporting evidence towards its feasibility in the near future.