The Monkey Business of Pure Altruism

September 27, 2013, 8:30 p.m. ET

The Monkey Business of Pure Altruism

ROBERT M. SAPOLSKY

I’ve been reflecting on how Bill and Melinda Gates resemble a pair of monkeys. Earlier this month, the Lasker Awards were announced. The prestigious prize, known as the “American Nobel,” is given annually to a few extraordinary biomedical scientists. A Lasker for public service is also usually awarded—this year to the Gateses. Great move. They’ve given vast sums of money to medical research and have galvanized other billionaires into doing the same. They’ve targeted research about diseases that bring incalculable misery to the developing world. All with great wisdom.Philosophers have long debated whether truly selfless altruism is possible. Some argue that pure altruism can occur, while others proclaim the jaundiced sound bite, “Scratch an altruist and a hypocrite bleeds.”

After all, altruism can be immensely fulfilling, and neuroimaging studies show that altruistic acts activate reward centers of the brain. Altruism also can enhance a giver’s reputation and prompt reciprocal gifts. And costly displays of prowess, evolutionary biologists have demonstrated, can serve to attract mates—”If I can afford to grow these gigantic antlers, I must have some studly genes.” Some scientists speculate that altruism evolved as a costly signal meant to impress prospective mates.

But there’s also anonymous altruism, with its glow from doing good by one’s internal standards. And there is cynically self-serving altruism. In 1892, the loathed robber baron Charles Yerkes found himself overextended financially; creditors readied their knives. Yerkes offered the fledgling University of Chicago an enormous financial gift—to be delivered in a few months but announced that day.

The press reported the plan and the confused creditors, fearing they had miscalculated Yerkes’s financial state, backed off. He recovered, profited and, as promised, gave the university what was for him a trivial sum.

Which brings us to monkeys, who spend hours each day sitting around, picking through each other’s fur. It’s a calming social glue that cements relationships. Grooming lowers heart rate, and my own work with baboons in Africa shows that animals who groom the most have lower stress hormone levels. It makes sense—you scratch my back, I scratch yours, we’re both happier.

An interesting twist to this story came with a study of Barbary macaque monkeys by Stuart Semple of London’s Roehampton University and colleagues. Monkeys who were groomed a lot didn’t have low stress hormone levels. Monkeys that groomed others a lot did. Dr. Semple’s work seemed to answer a question contained in the paper’s title: “Better to give than to receive?” In other monkey species, too, grooming decreases the behavioral markers of anxiety in the groomer. So monkeys, who don’t care about charitable tax write-offs, are less stressed when they give, rather than when they receive.

Now for a killjoy alternative: Scratch a grooming altruist, and maybe you’re scratching a happy monkey with a stomach full of yummy parasites from the other monkey’s fur. Supporters of pure monkey altruism respond by noting the minimal nutritive content of grooming-derived parasites. And skeptics of pure altruism note how grooming builds beneficial social networks.

And besides, how do you know that being a generous groomer lowers a monkey’s stress hormone levels? Maybe monkeys with low levels are relaxed enough to be charitable groomers. In other words, more research is needed.

I’m not voting as to whether pure altruism exists in other primates. Who wants to invite the snarky, dismissive remarks of philosophers? I merely want to thank the Gateses. The next time I hear some blowhard Barbary macaques bragging about their moral superiority, there are at least two humans I can point to with pride.

A version of this article appeared September 28, 2013, on page C2 in the U.S. edition of The Wall Street Journal, with the headline: The Monkey Business of Pure Altruism.