So many animals have the same motherly instincts?

Question

Has the gene(s) been identified for young protection?

Many species of vertebrates instinctively defend their young in a simlar way. Is there a common gene(s) for this protectiveness?

Answer 1

It is thought that oxytocins and similar chemicals cause our brains to temporarily turn to Jello [TM] when we see mammal larvae, and thus keep us from eating our young (which would be the purely rational approach to survival of the individual, after all).

The genes that enable us to produce those chemicals have been identified. So the answer to your questions seems to be "yes".