When Altruism Defies Evolutionary Logic

Adoption is very common in the human species even though you don’t get much back from it.


There’s this story that we humans are only altruistic, and that animals are only altruistic either toward kin with whom they share genes or toward individuals who will pay them back one way or another.  This doesn’t explain a lot about human altruism.  

For example, people will care for an elderly spouse who is terminally ill. There’s very little chance of repayment, but people show that kind of altruism all the time.  Adoption is also typical. Adoption is very common in the human species and you don’t get much back from it.  And actually you’re investing an enormous amount of time of your life into a being who is not genetically related to you.

So this is a very puzzling kind of altruism and interestingly enough it occurs in the primates also. For example, in Ivory Coast there is documentation of ten cases of adoption by males, adult males, who have adopted an orphan chimpanzee.  So the chimpanzee loses its mother. Chimpanzees are dependent on their mother for at least eight years of their life.  So if you lose your mother at three years of age you may be able to, as a chimpanzee, to survive on solid food but you still need to be carried and protected and someone needs to “explain” to you what to eat and what not to eat.  And adult males are willing to do that and they have DNA data on those males and those babies and they’re not necessarily related.

Sometimes one male adopted a young chimpanzee for five years.  So they spent an enormous amount of time and energy on individuals that they don’t get much back from.  And I find that very interesting.  These cases of altruism don’t fit any evolutionary scenario but nevertheless occur.

In Their Own Words is recorded in Big Think's studio.

Image courtesy of Shutterstock

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