Hello, I’m Wang Fang. The atmosphere of year’s end grows stronger, and I am eagerly anticipating the holiday. Anticipation is a light in ordinary days; I hope you too always have something to look forward to.

Today is a long bonus episode. Last time we discussed evolutionary psychology, and I explicitly opposed the crude, mistaken application of biological evolution to society known as Social Darwinism. Social Darwinists glorify competition everywhere, yethuman beings are a highly social species and often act to benefit others at potentially high cost to themselves: generously helping strangers and even sacrificing themselves. Evolutionary psychology sees precisely these behaviors as products of natural selection.

I have recently been reading an interesting evolutionary-psychology book, The Social Leap by William von Hippel; its Chinese title means When We Throw Stones at Lions Together.

What does throwing stones together mean? Millions of years ago, climate change moved our hominin ancestors from forest canopies to savannas. With nowhere to hide, survival became much harder. Our ancestors had weak bodies, slow running speed, and pitiful fighting power, yet faced giant predators everywhere ready to eat them. Survival seemed impossible.

When a predator was about to pounce and neither hiding nor escape was possible, what could they do? The answer:unite, defend together, and throw stones at the lion together.This could repel predators much stronger than any individual—the so-called stone-throwing hypothesis. A group that cooperated instead of fighting internally or looking only after itself enjoyed better survival, as did every member. In other words,cooperation, interdependence, and mutual assistance increased individual and group survival and were selected by evolution. More importantly, cooperation rapidly developed humanity’s social brain and engraved sociality into our nature.