Correction to This Article
With a Science article in some March 19 editions, captions for photographs of a warbler and a cowbird were reversed.
Behavior May Suggest We're Not Only Human

By Shankar Vedantam
Washington Post Staff Writer
Monday, March 19, 2007

When Emory University primatologist Frans de Waal read a news story that said Microsoft's chief executive, Steve Ballmer, had hurled a chair across the room on hearing an employee was going to work for rival Google, the scientist immediately made a connection with his own research: "When I see such behavior, I think of a chimpanzee."

Another time, a researcher that de Waal knew told him that whenever she chatted with another scientist in the hallway, her boss would get upset. He would later drop by her office and tell her she ought to stay clear of that person.

"He was constantly interfering whenever she had a contact with an important person," de Waal said. "Chimpanzees also divide and rule. You have an alpha male, and he will try to keep his supporters away from his rivals. His supporters are in trouble if they groom one of his rivals."

Does such behavior make you laugh? Well, if de Waal and other scientists are right, you may have to address some of your mirth to that face in the mirror.

Over the past two centuries, people have had to disabuse themselves about various ideologies asserting that humans are fundamentally different from other animals. Biologists have shown that our arms and legs and organs have long evolutionary histories. Beliefs about the uniqueness of human behavior might well be the last bastion of our superiority complex, but research by de Waal and many others suggests that even this redoubt may be crumbling.

"I have done studies of reconciliation and coalition strategies in chimpanzees," de Waal said. "Business managers tell me that reminds them so much of what people do."

The idea that human behavior -- not just our physical bodies -- may have long evolutionary antecedents raises complicated questions about human agency and about how much of what we do and think is hard-wired. It is one thing to say we have eyes because our ancestors had eyes, but should we also credit our evolutionary predecessors for our highly complex social and political arrangements?

Scientists such as de Waal argue the research suggests that, much as people believe in the originality of their thoughts, a lot of human cognition probably takes place at an automatic level, guided by inborn tendencies. About the woman with the possessive boss, for example, de Waal said: "I am sure her boss is not consciously doing that. It just bothers him if she has a chat with a rival."

Two recent studies from the world of birds give us a glimpse into how far back in evolutionary terms complex behaviors that we would normally associate with humans go. One of these behaviors has a nice altruistic aspect to it. The other, not so much. But more on the morality question later.

Emily DuVal, a biologist at the Max Planck Institute for Ornithology in Germany, found that male lance-tailed manakins display the behavior seen at nightclubs, where a person plays "wingman" or "wingwoman" to help a friend impress a potential mate.

In a study of 457 lance-tailed manakins in Panama, DuVal found repeated instances of two males performing a skilled dance for the benefit of a female bird who was watching. The group performance, however, helped only one of the birds -- the alpha male. If only one lance-tailed manakin got to mate, why did the other bird, the beta male, cooperate in the dancing ritual when he had nothing to gain?

In a paper she published in the April issue of the American Naturalist, DuVal found there is evidence that good "wingbirds" are more likely than other birds to become alpha males themselves. What makes the behavior especially interesting is that one lance-tailed manakin might be helping another because some other bird will help the helper down the road. Such behavior suggests an intricate social system where investments pay off in the distant future.

In another study, Jeffrey Hoover, an avian ecologist at the Illinois Natural History Survey in Champaign, found that cowbirds have a lot in common with gangsters.

It all began, he says, when ecologists started removing the eggs of cowbirds from the nests of warblers. Cowbirds leave their eggs in the nests of dozens of other birds. It has long been a mystery why birds such as warblers allow the eggs to hatch and why the hosts then feed the young cowbirds -- sometimes at the expense of their own offspring.

Hoover and colleague Scott Robinson found that when they removed cowbird eggs from the warbler nests, those nests mysteriously got trashed. Turns out that the cowbirds, much like members of the mob, were keeping a close eye on the nests in which they had laid their eggs. If anything bad happened to the eggs, the cowbirds would return and destroy the nest.

Hoover found that, much like the way the mafia operates, the cowbirds begin with detailed surveillance of their potential targets. That is because if a cowbird lays an egg in a warbler's nest before the warbler has laid any eggs of her own, the warbler can simply fly somewhere else and establish a new nest, and the cowbird will not be able to retaliate. On the other hand, if the cowbird lays its egg after the warbler has finished laying all her eggs over a period of three to five days, the warbler's hatchlings will emerge sooner than the cowbird's and thereby gain a size advantage in grabbing all the available food.

Hoover found that after monitoring a warbler's nest for a period, a cowbird will lay its egg in the nest right after the warbler has started laying its eggs. Cowbirds can lay 10 to 15 eggs at a time in different nests, and it appears that after laying each egg these birds then make the rounds to ensure that all the warbler hosts are toeing the line.

Cowbird eggs often look very different from the eggs of the birds whose nests they parasitize, which is why scientists had wondered why the host birds simply did not chuck those eggs. In a paper Hoover published online in the Proceedings of the National Academy of Sciences, he found that warblers that accepted the cowbird eggs produced three offspring on average. When the researchers removed the cowbird eggs from the nests, these warblers produced only one offspring on average because the cowbirds would return and trash most of those nests.

"What is interesting is the female cowbirds are running this mafia-like racket," Hoover said. "People often think of males as being violent. . . . The male cowbirds play little or no role in this."

All of this raises interesting questions. If a human playing wingman or wingwoman for a roommate is doing what the lance-tailed manakin has done for thousands of years, how much conscious thought is actually necessary for such behavior? And could the Tony Sopranos of this world plead not guilty by virtue of evolution?

Frans de Waal argues that there is a difference between cowbirds and human gangsters. A Tony Soprano knows what he is doing and understands the consequences. "The birds may not even know what reproduction is," he said. "They are not thinking, 'If I trash the nest, next time they will be careful.' "

Or . . . are they?

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