In an earlier post, I list some of the remaining mysteries in evolutionary psychology, which I initially listed in the final chapter of our book Why Beautiful People Have More Daughters. My friend and LSE colleague, David de Meza, has just suggested a potential solution to Remaining Puzzle #7: Why children love their parents.
As I explain in the earlier post, parents have been selected to love their children, whether children love them back or not, in order to motivate the parents to invest in the children and to increase their reproductive success. It is not necessary for the children to love their parents, as parents are evolutionarily designed to love their children regardless of whether children love them back or not. Hence the mystery.
However, David points out that, given that parents already love their children, children who love their parents and thus invest in them are expected on average to do better than children who don’t love their parents and thus do not invest in them. This is because, given that the parents love their children unconditionally, a large proportion of resources invested in the parents will be transferred back to the children and their children, the parents’ grandchildren. So the children of people who love and invest in their parents on average receive greater resources than the children of people who don’t love and invest in their parents. Hence a tendency of children to love and invest in their parents will be selected and spread throughout the population.
Of course, children only share half their genes with their parent, the same proportion as they share with their own children or full siblings. So, reproductively speaking, investing resources in a parent is at most only as good as investing in their children or siblings. Further, one’s children and siblings are expected to live much longer (and have much longer remaining reproductive life) than one’s parent, so investing in children and siblings should always be better than investing in their parents.
However, David points out that, once their children and siblings are fed, clothed, and otherwise taken care of, investing further resources in them will have diminishing returns, and resources might be better used by investing them in their parents. If the parents live longer and stay healthier, they can be around to look after their grandchildren or even great-grandchildren, thereby increasing the individual’s reproductive success.
David’s explanation not only explains why children may love their parents, but predicts that people will never love their parents more than they love their children and siblings. Any resources that individuals acquire should first be invested in their children and siblings, and, only after they are well taken care of, in their parents. I think this is largely consistent with our casual observations.
David suggests that his explanation is just a variant of the Nobel prizewinning economist Gary S. Becker’s famous “Rotten Kid Theorem.” Becker argues that even a rotten kid, who is not inclined to be altruistic toward his family members, will be altruistic if he knows that he will, for example, inherit more money from his parent if he behaves altruistically toward other family members. There is, at least in my mind, a deep philosophical distinction between microeconomics, which often posits that human actors make rational decisions (although their standard line, attributable to another Nobel prizewinning economist Milton Friedman, is that humans act “as if” they make rational decisions), and evolutionary psychology, which posits that all decisions are in essence made by evolution and humans don’t really make any conscious decisions. For example, Becker’s rotten kid makes a calculated decision to be nice to
his family members because he consciously expects to receive greater inheritance and other benefits if he did; in other words, he’s not really nice. (If he were truly nice, he would not be a rotten kid in the first place.) In an evolutionary psychological view, if David is right, children are evolutionarily designed to be nice to their parents; in other words, they are genuinely nice. But I do see a logical connection between Becker’s “Rotten Kid Theorem” and David’s explanation for why children love their parents.
I think this might be the solution to Remaining Puzzle #7. At least it is not a complete mystery any longer. One down, seven more to go. (It’s actually more than seven, because Puzzle #9 contains a few different puzzles within it.) Onwards and upwards. Wir müssen wissen, wir werden wissen.
