Wednesday, October 2, 2013

The Monkey Business of Pure Altruism

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.

- Robert Sapolsky

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