WHY DO CHIMPANZEES ADOPT?
Here’s a stumper: Normally, a male chimp doesn’t pay much attention to his kids. That’s women’s work. But in the wild, males are ready, willing, and able to adopt orphaned chimps. What gives?
The observation comes from three different groups over a period of 27 years. During that time 36 youngsters were orphaned, and half of them were adopted by other adults. And males were just as likely to take in a foundling as females. (The other half perished. Many were very young and unweaned.)
It’s not a trivial act. Adoptive parents spend time waiting for their kids as the group travels through the forest. When the kids tire, they carry them. they share food with them. They protect them. And adoption can even lead to harassment of the adult: Adult bullies will tease or attack the orphan to stir up the adult.
Animals (us included) aren’t supposed to do anything that undermines our own fitness. We’re not supposed to waste our energy on anyone who isn’t carrying at least a chunk of our DNA. That’s just biologically dumb. As social animals, we and the chimps both have to make some concessions to the group good, but let’s not go crazy with that.
For male chimps who hardly bother with their own offspring to so far as to take in an unrelated stray seems batty.
Two possibilities:
1: Female chimps mate promiscuously when they’re fertile. One theory is that they do this to keep the males guessing. A males is unlikely to attack that female’s offspring if there’s a chance it’s his. So some males may simply assume that every kid might be theirs.
2: Among social animals like humans and chimps, some individuals are more social than others. Those of us wired for high sociality are sensitive to others’ needs and troubles, suckers for a sad face. Perhaps the adopting males are the bleeding hearts of the group, and they can’t turn away from a child in need even when there’s a price to pay.
