Saturday, August 12, 2017

Wisdom Of The Week

If Adam Smith had strapped on a bee suit—or a safari jacket, or a scuba mask—he could have discovered that the animal kingdom is, in fact, a chamber of commerce. “Biological markets are all over the place,” says Ronald Noë, a Dutch biologist at the University of Strasbourg who first proposed the concept of the biological market in 1994. Scientists have since described biological markets in the African savannah, Central American rainforests, and the Great Barrier Reef. Baboons and other social primates exchange grooming for sex. Some plants and insects reward ants for protection. Cleaner wrasses eat parasites off other fish and behave more gently when a “client” has the option of visiting a rival wrasse.

These discoveries have not just deflated economists’ anthropocentrism but have challenged biological dogmas as well. “We all learned not to treat animals in an anthropomorphic way, but a theory that was produced to explain human behavior nevertheless matters in biology,” says Peter Hammerstein, Noë’s co-author and a professor of theoretical biology at the Humboldt University in Berlin. “In fact, I believe some of it works better in biology than in humans.”

Noë began to think about economics in biology in 1981 as he worked on a post-doctorate degree in Kenya. “A big baboon gave me the idea,” he says. Baboons live in large hierarchal groups, and Noë was interested in when and how low-ranking males teamed up to challenge a more dominant male to mate with a female. Cooperation was common in nature—not just between animals of the same species but also between different species (for example, a plant and its pollinator). But the origins of cooperation were a mystery. How could two animals work together when Darwin’s theory of evolution taught about survival of the fittest? Shouldn’t natural selection always favor ruthless self-interest?

“It was one of the early questions in behavioral biology,” says Hammerstein. “Why do animals not always kill each other? Why is aggression limited?”

When Noë began his fieldwork, behavioral biologists proposed two theories for cooperation. The first, called “kin selection,” held that an organism could sometimes better propagate its genetic material by helping a close relative reproduce rather than trying to reproduce itself. An ant colony, for instance, has a huge number of sterile female workers who help raise the young of a kindred queen. But kin selection couldn’t explain why a fish such as the cleaner wrasse can pick parasites from the teeth of a barracuda with almost no risk of becoming a meal itself. They shared no genes, so a predator ought to reap a dual reward by eating the dentist after the cleaning.

“Reciprocal altruism” was the second main evolutionary theory for cooperation. Biologists argued that natural selection could favor cooperation between two organisms that interact repeatedly over their lifetimes. One individual conferred some benefit on the other, knowing that the benefit would be repaid down the line. The crux of reciprocal altruism was the idea of partner control. How could an altruist guarantee that his partner would return the favor?

To answer this question, biologists looked to game theory, which sought to model conflict and cooperation strategies between self-interested individuals. The most famous example was the two-player game called the prisoner’s dilemma, and biologists used it to write elaborate formulas for how reciprocal altruism might have evolved. “It was all theoretical papers stacked on top of each other, and at the bottom there was no empirical evidence,” Noë says. “I’m inclined to look at what real animals do.”


In 1994, Noë and Hammerstein laid out their new theory of biological markets in the journal Behavioral Ecology & Socialbiology. The paper fused the biologists’ different styles: Hammerstein developed the mathematical models, while Noë dug through the scientific literature for evidence from the field. Examples turned up across the animal kingdom. Male scorpion flies offer females a “nuptial gift” of prey before mating. In some species of bird, such as the purple martin, a male will allow another male to occupy part of his territory in exchange for help raising his young. Lycaenid butterfly caterpillars produce a sweet “nectar” whose only purpose is to attract ants, which eat the nectar and protect the caterpillars from predators.

In each example the “exchange rate” is not fixed but rather contingent on the supply of available partners. “It is essentially a supply-demand theory,” says Frans de Waal, the eminent primatologist from Emory University and a former mentor of Noë. The more male scorpion flies available on the market, the larger the nuptial gift the female will demand. The male purple martin chooses the most juvenile-looking and least threatening tenant. And the caterpillars adjust the amount of nectar they produce to the number of ants in the vicinity.

Noë and Hammerstein felt their paper laid out a radical new way to understand cooperation in nature, but there was not much immediate enthusiasm from their peers. “Because it was not in the big journals, it took off very slowly,” Noë says. The new theory inspired some of their students, though, who took it into the field. “I thought this is such a different way of looking cooperation and it made intuitive sense,” says Redouan Bshary, a professor of behavioral ecology at the University of Neuchâtel in Switzerland. Although he had trained with Noë in primatology, Bshary learned to scuba dive so he could study the animal that had long fascinated biologists who study cooperation: the cleaner wrasse.

Cleaner wrasses are small, ribbony fishes with black racing stripes from eye to tail. They aren’t the flashiest fish on the reef, but they are perhaps the cleverest. Each wrasse occupies a “station” on a piece of coral, which other fish visit when they are feeling crusty. The wrasses eat the dead skin and parasites off their clients, but not all clients receive equal treatment. Some clients have to wait longer than others, and a wrasse sometimes spices up its diet by sneaking a painful bite of healthy scales and mucus.

Bshary believed that market forces could explain the differences in service quality. He began his research in the Red Sea, where he divided the wrasses’ clients into two categories: the floaters with big ranges, who could travel between several cleaning stations; and the residents with small ranges, who couldn’t reach more than a single cleaning station. Floaters would be able to shop among stations, Bshary reasoned, while residents would not. Indeed, Bshary found that the floaters almost always received prompter and gentler treatment. The wrasses made residents wait longer for cleaning and were also much more likely to munch on residents’ healthy scales and mucus, demonstrating another well-known law of economics: Monopolists are jerks.

The Secret Economic Lives of Animals

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