Male mountain gorillas don’t seem to know or care which young are theirs. But nearly all males tolerate the company of kids. Unlike any other great ape that’s been studied in the wild, these males—bruisers twice the size of females, with huge muscles and teeth—are essentially babysitters. Some pick up the kids, play with them and even sleep cuddled together.
This male company can protect very young gorillas against predators, and it keeps the young from being killed by intruding males. Another important benefit might be social, [biological anthropologist Stacy] Rosenbaum speculates.
She’s found that male gorillas who do more babysitting earlier in life go on to father many more children when they’re older.
Studies of human dads and stepdads have hinted at the same idea. “A lot of guys will willingly enter into relationships with kids they know aren’t theirs,” says Kermyt Anderson, a biological anthropologist at the University of Oklahoma. That investment might seem paradoxical from an evolutionary perspective. But Anderson’s research suggests that men invest in stepkids and even biological kids partly as an investment in their relationship with the mother.