As I understand it, scarring and regeneration are mutually exclusive. The advantage of regeneration is that you get the body part back. The advantage of scarr

As I understand it, scarring and regeneration are mutually exclusive. The advantage of regeneration is that you get the body part back. The advantage of scarring is that you don't bleed to death or get a fatal infection while waiting for the wound to close. In larger animals, formation of scar tissue had a greater survival advantage. So humans scar instead of regenerating. The regeneration capacity is probably all still there in humans, but it is never been observed in modern times, except after losing less than about 1 cm of fingertip. It may not be a matter of how to turn regeneration on, but how to turn scarring off.