Natural selection can favor genes that allow children to grow up healthy. But in order to grow up healthy, they need nurturing from their mothers, both before and after birth. If a baby’s development puts a strain on a mother, she may end up having fewer children. That means she may spread fewer copies of her genes to later generations . That creates conditions in which natural selection may also genes that allow mothers to restrain their children. Our particular way of having kids puts genes in conflict.

I have an article in tomorrow’s New York Times on these conflicting genes, focusing on the visionary work of David Haig of Harvard University. As I explain in the article, Haig