Chapter Eight

In June 2017 I traveled to Jamaica to interview Robert Trivers, who owns a house on six wooded acres on a hilltop near the island’s southern coast. Unwisely, perhaps, I talked my girlfriend, whom I’ll call Emily, into coming with me. She rolled her eyes when I called Trivers one of the greatest living scientists. You say that about everyone you interview, she said. What sold her on the trip was the prospect of relaxing on a Caribbean beach. We arrived at Trivers’s home early one evening and departed the next afternoon for a resort in Negril. During that time, my reactions to Trivers swung wildly between admiration, pity and fear. They still haven’t fully stabilized.

A couple of scenes to convey the man’s complexity. Giving me and Emily a tour of his land, Trivers pointed out a bulbous, spikey, bright green fruit dangling from a tree. It looked like the business end of a medieval mace. That tree is Annona muricata, called soursop by locals. Natural selection gave the fruit its distinctive shape for easy night-time detection by bats, which devour the fruit and excrete the seeds. Clever, eh? Trivers makes soursop tea by boiling the leaves in water and adding sugar and milk. The brew calms the nerves and helps you sleep.

We paused before another tree with bronze bark and dark, glossy leaves. A pimento, Trivers said, which produces allspice. The tree is unusual because it is dioecious, plants are either male or female. Most flowering plants are monoecious, each plant has male and female organs and hence can pollinate itself. The dioecious system is much less efficient, because male trees contribute so little to reproduction. Gazing fondly at the pimento, Trivers mused, “That these things survive in competition with other species is something of a mystery.”

Fruit of Annona muricata.

Later, when I was alone with him in his living room, Trivers displayed knowledge of a different kind. If someone pulls a knife on you, he informed me, cross your arms in front of you, like this. Wait for your assailant to make his move, knock his knife hand aside with a forearm and punch him or go for his throat. He showed me a chokehold he learned from his pal Huey Newton. Gripping the back of my windpipe between his thumb and fingers, Trivers pinched until I winced. He apologized for hurting me, but did I understand how it would feel if he had squeezed hard? This hold can incapacitate any man, no matter how big and strong, and kill him if you keep squeezing. Massaging my throat, I indicated my appreciation for the lesson by nodding and grinning like a submissive ape.

Before I return to this tropical tale, some background. If you believe in science, as I do, you accept that natural selection created us. Whatever mind-body story you favor—integrated information theory, strange loops, Bayesian models, quantum consciousness, psychoanalysis—you must acknowledge that we are organisms designed for one purpose, making copies of ourselves. That, according to evolutionary biology, is who we really, truly are.

I nonetheless have a deep-rooted bias against biological explanations of human behavior. I fear they will discourage us from trying to create a better world by convincing us that the way things are is the way they must be. Historically oppressors, notably white, western, upper-class males, have invoked evolutionary theory to justify racism, sexism, imperialism, militarism and rapacious capitalism. Hierarchical social structures and inequality are inevitable. Those in power deserve it, because they are fitter.

Even Darwin, enlightened for his era, confused what is with what ought to be. In The Descent of Man he wrote that man displays “a higher eminence, in whatever he takes up, than woman can attain–whether requiring deep thought, reason or imagination.” This sort of thinking is not as overt as it once was, but it endures. It is invoked to explain why males have dominated science, mathematics and the arts.

Many evolutionary hypotheses deserve to be derided as fanciful “just-so stories,” if not racism and sexism in scientific guise, but not the hypotheses of Trivers. In 1971 he took on one of biology’s deepest mysteries in “The Evolution of Reciprocal Altruism.” Altruism consists of helping others at a cost to yourself. It is the essential moral act. Altruism toward those who share our genes is easy to explain in Darwinian terms, but why are we kind to non-kin, including strangers? Why jump in a pond to save someone else’s drowning kid? Why does my niece, a Harvard Law School graduate, work as a public defender in North Carolina, helping poor people accused of crimes, when she could make much more money as a corporate mercenary?

Trivers conjectures that natural selection instilled compassion and other moral emotions in us because our ancestors–over time and in the aggregate—received tit-for-tat benefits from acts of generosity. The emotions are instinctual, the end result of millennia of calculations by natural selection. But altruism could only propagate if natural selection instilled complementary tendencies in us, such as an exquisitely honed sense of fairness. If someone is kind to us, we feel grateful, and we want to reciprocate. If we are mean to someone who has treated us well, we feel guilt. We become outraged if we sense that someone is “cheating,” taking advantage of our kindness or that of others.

The emotions and instincts that nudge us to be kind, and to repay acts of kindness, might be absolutely sincere. But we are not just creatures of emotion and instinct. We also consciously, and rationally, help others with the expectation of reward. Worse, we deceive others about how generous and kind we are. We fake being good to get the benefits without the costs. Trivers backs up his thesis with elegant mathematical modeling, based on game theory, and examples of altruism-related behaviors in birds and fish. His reciprocal-altruism model, he points out, provides insight into “friendship, dislike, moralistic aggression, gratitude, sympathy, trust, suspicion, trustworthiness, aspects of guilt, and some forms of dishonesty and hypocrisy.” Trivers isn’t bragging, just stating a fact.

In two subsequent landmark papers, “Parental investment and sexual investment” (1972) and “Parent-offspring conflict” (1974), Trivers explains why hatred and cruelty abound even within families. Parents share no genes with each other and only half their genes with offspring. A female can only produce offspring every nine months. A male can in principle have virtually infinite offspring, but he cannot be sure a child is his. Given these genetic conflicts of interest, it is not surprising that parents sometimes become bitter enemies and even abandon offspring. These papers could serve as an appendix to What Maisie Knew, in which parents behave atrociously to each other and to their daughter, and to Alison Gopnik’s books on kids.

“The human altruistic system is a sensitive, unstable one,” Trivers writes. That could be the greatest understatement in the history of science. The ideas of Trivers were rapidly popularized by other biologists, notably Edward Wilson in Sociobiology and Richard Dawkins in The Selfish Gene (for which T