Can animals' cooperative instincts help build a better human?

BY LAURA TANGLEY - US NEWS

"As a hungry hawk circles overhead, a Belding's ground squirrel rises up on her hind legs and emits a piercing alarm call, risking her life to warn others of the impending danger. Even at personal peril, a male baboon helps another male fight off a third male courting a female, then sits aside and lets his pal have her all to himself. Some ants, bees, and rodents give up the chance to reproduce altogether, devoting their entire lives to helping others raise offspring instead."

Ever since Charles Darwin introduced the theory of evolution by natural selection in 1859, such self-sacrifice among animals has puzzled biologists. According to Darwin, organisms with traits that provide a competitive edge–a longer neck to reach leaves on a higher branch, for example–are apt to live longer and produce more offspring than others. How, then, can a trait that decreases one's chances of surviving and reproducing ever evolve? Evolutionary biologists have now identified four "paths" to the rise of cooperation in animals. In a new book, Cheating Monkeys and Citizen Bees: The Nature of Cooperation in Animals and Humans (The Free Press, $25), University of Louisville biologist Lee Dugatkin presents the latest evidence to support these theories, which range from self-sacrifice for the sake of family members to cooperation based on the expectation that a favor will be returned in the future.

But Dugatkin also goes a step further, suggesting that research on animal cooperation can provide clues for making people more cooperative. Although he realizes this leap will rankle at least a few scientific colleagues, who are loath to extrapolate from human to other animal behavior and vice versa, Dugatkin points out that insights gleaned from animal research already have proved useful for understanding human predicaments ranging from cancer to aging. "Arguing that animals can be model species for physiological but not behavioral traits is illogical," he says.

Darwin himself observed self-sacrificial behavior among certain bees and wasps, which stung intruders to protect their nest, dying soon afterward. He suspected that the explanation had to do with the fact that insects in a single nest are closely related–and therefore carry many of the same genes–so that an individual who gives her life for the colony helps to pass on more genes than if she had lived.

Now called "kin selection," this theory explains why many ants, bees, and wasps, which by virtue of a bizarre genetic system are more related to their sisters than to their offspring, refrain from breeding to help the queen raise her young. Biologists have learned that risk-taking ground squirrels also are related to their nest mates, and that females, which remain with their kin, take the greatest risks.

But most animals that appear to make sacrifices for others do so for nonrelatives. To explain some such cases, biologists have developed a second theory, "reciprocal altruism," or, in Dugatkin's words, "You scratch my back; I'll scratch yours." As a graduate student, Dugatkin began studying cooperative behavior among wild guppies, which regularly break away from their schools in pairs to "inspect" dangerous predators. He wondered why one of the fish never hung back and let its partner take all the risk, as old-fashioned natural selection predicts. Mathematical models and experiments, including Dugatkin's, have now shown that such seemingly illogical selflessness can evolve in a society where individuals are able to exchange favors over a long period of time, retaliating against partners that "cheat." Other examples include male baboons that alternate helping one another fight off competitors for a receptive female and hermaphroditic fish that take turns releasing either sperm or eggs (eggs being a costlier investment) when the two get together to reproduce.

Costs and benefits. Most scientists stand firmly behind both reciprocal altruism and kin selection, but a third theory, "group selection," remains controversial. Because it holds that cooperation can evolve as long as an individual's cost is offset by benefits to its group, the theory is heresy to biologists who believe that natural selection operates only at the level of individual organisms.

Group selection's proponents say one of its most convincing examples comes from Sonoran desert ants called Acromyrmex versicolor, which–unlike many ant species–live in nests containing several unrelated queens. Over and over, a single queen leaves the safety of the nest to gather food for the entire colony. Some biologists say this self-sacrificial behavior evolved because colonies of A. versicolor, once they have raised their offspring, emerge from the ground en masse to engage in all-out warfare with other nests. Colonies made up of the strongest workers (those that are well fed) tend to win, so group benefits may be so strong that genes for the risky but effective role of sole food-gatherer have spread.

For cases of cooperation that do not neatly fit into any category, however, biologists increasingly suspect that the behaviors are little more than side effects of plain old selfishness–a theory dubbed "byproduct mutualism." Hunting lionesses, for instance, were long considered a classic case of "unconditional cooperation." But recent research in Tanzania's Serengeti National Park has shown that lionesses hunt cooperatively only when they are stalking prey so large that a single predator cannot bag it alone–or when the immediate benefits to the individual outweigh the costs. "We tend to look for the jazzier explanations," says Dugatkin, "but many animals may cooperate only when it's in their own best interests."

What about the human species? For centuries, philosophers have debated whether people are by nature cooperative. Yet even if cooperation does not come naturally, most agree that it is the glue that holds societies together. Dugatkin believes that, as "a stripped-down version of what behavior would look like without moral will and freedom," animal cooperation can provide clues to fostering better human behavior.

As an example, he cites the case of partnerships in risky professions such as police work or military guard duty. Lessons derived from animals that cooperate through reciprocal altruism suggest that the key to the relationship's success, beyond individuals being able to recognize and remember each other, is that both partners know the pair will be interacting for long periods, with no known end point. Similarly, kin selection predicts that enemy nations, tribes, or other groups will interact more cooperatively if they share one or more related individuals.

Yet even some firm believers in the power of natural selection doubt that nature can help build a better human. "Good luck," says Robert Trivers of Rutgers University, the evolutionary biologist who first developed the theory of reciprocal altruism in the 1970s. Dugatkin himself acknowledges that "humans, of course, are far more complex than other animals." Still, he believes that three decades of research on dozens of cooperative creatures provides an "untapped treasure chest of data that we'd be foolish to ignore."

Paths to cooperation

Evolutionary biologists have identified four forms of cooperation in animals.

Kin selection. An individual will risk its life to protect close relatives, who most likely carry the same genes.

Reciprocal altruism. By exchanging favors within a group over a long period of time, individuals help each other. They also shun those who don't participate in the trade process.

Byproduct mutualism. By joining forces to achieve a difficult goal, each animal gets what it wants.

Group selection. An individual takes on risks when they provide clear benefits to its entire group.

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