“Years later, I read that someone had found genetic components to good motherhood. The Mest and the Peg3 genes occur on chromosome 19, and, ironically, they only work if they’re inherited from the father. Imprinting like this usually occurs in evolution because of a genetic battle of the sexes; it’s in the best interests of the female to have more litters, but it’s in the best interests of the male to protect the child that’s already been born. The jury is still out on these.”
