Reply #14: Perhaps I'm not explaining myself well at all - seemed perfectly clear to me though

[txlibdem]

Oops! My apologies.

You said, "Animals missing a limb may typically find it hard to get food, and to survive need to conserve their energy." This is exactly the point I am making but there's more to it than that. How long would it take a Human to regrow a lost leg or arm versus how long one can survive without food? Early Man could not simply conserve energy during limb regeneration: they would starve long before that. So they would need to attempt to go out and forage for food, becoming an attractive target to predators and being unable to run as fast or be unable to climb trees to escape teeth and claws, they would fall to predation.

Our genetic makeup was largely set by the time social structures, fire and weapons all developed sufficiently that a totally dependent person could be fed, cared for and (most importantly) protected from predators, without causing harm to the group as a whole.

So, regardless of age, prior to that time the severely injured or those with lost limbs would have died in short order due to predation or would have starved to death. Since the young would be naturally slower and less able to outrun predators they would be much more often targeted for predation, would be more likely to lose a limb or suffer severe injury or loss of limb, they would be even slower during regeneration -- even more greatly selecting for the activated gene. Then, too, the social group that cared for an individual so afflicted could only gather so much food themselves and caring for an unproductive member would remove food from everyone in the group so that, too, could affect the survival of the group as a whole or of their healthy offspring, thereby further selecting for the active gene.