Wednesday, June 27, 2007

Basic Instincts: Life on Two, Four, Six and Eight Legs

The other day in an interview in The New York Times Magazine, Al Gore’s daughter Kristin revealed that when she was a child, she couldn’t stand to think about wrists. All those veins and tendons. Probably didn’t like to gnaw chicken bones either. Too squeamish.

And when her sisters found out, did they promptly don four-button gloves out of sympathy and respect, to spare their delicate sister the dreadful sight? On the contrary, they waved the naked veiny insides of their wrists in her face. The horror, the horror.

But this is what siblings do, isn’t it?

The strange nature of the sibling relationship has been in the news a lot lately. A study last week, for instance, demonstrated that first-born children, those conscientious overachievers, really do turn out smarter than second-borns, and this predictably stirred up lots of preening and muttering, respectively.

But the sibling news that really caught my attention had to do with the origins of altruism, and also its seeming opposite, our tendency to band together in groups and gleefully crush the enemy — the best and worst in human nature. And the explanation put forward last month — “nested tug-of-war” theory — sounded a lot like family life as we know it.

O.K., there’s a caveat: Like a lot of the best behavioral theorizing, the paper by H. Kern Reeve at Cornell and Bert Hölldobler at Arizona State University, published in the Proceedings of the National Academy of Sciences, was actually about ant siblings, not people. But we can read between the lines.

The paper suggested that the dynamic of groups is a constant back-and-forth between one tug-of-war nested inside another. The first tug-of-war is selfish competition for resources within the group. The second is the group’s competition with rival groups. And here’s the startling part: Self-sacrificing devotion to the group, meaning cooperation and altruism, is largely a byproduct of kill-the-enemy competition.

An old Arab saying puts roughly the same idea in a family context: Me against my brother; my brother and me against our cousins; our cousins, my brother and me against the world. But anybody who grew up with siblings knows the feeling. Karenna and Sarah Gore might well have flashed their wrists at sister Kristin. But if some non-family member tried it … well, closing ranks against outsiders is also what siblings do.

Scientists have been trying to explain the origin of altruism and cooperative behavior for decades now, on the theory that the urge to give away resources and individual advantage would never have become part of human nature unless it provided a benefit to individuals displaying the trait.

But none of the familiar scientific explanations has really hit the mark: For instance, reciprocal altruism says we do it out of I’ll-scratch-your-back-you-scratch-mine self-interest. (But then why do we leave a fat tip in a restaurant we never intend to re-visit?) Kin selection says we help close relatives because it’s a vicarious way to get more of our shared gene pool into future generations. (So why do we also help total strangers?) And handicap theory says altruism is just a big gaudy show of prowess, to attract mates. (Yes, but then why do some donors remain anonymous?)

The new theory got its start when two celebrated co-authors, Hölldobler and the Harvard biologist E.O. Wilson, who won the Pulitzer Prize for their 1990 book “The Ants,” couldn’t get past the altruism question while collaborating on a new book. The two of them published a paper together in 2005 wondering aloud if natural selection might actually operate at the group level, favoring colonies or tribes that muster the highest level of internal cooperation and altruism.

This was, by Wilson’s own admission, heresy. Evolutionary biologists have been arguing adamantly for the past 40 years that the rough-and-tumble of life favors individuals, not groups, to pass on their genes to future generations. But individual selection didn’t adequately explain the behavior of highly social and cooperative species like humans or especially ants, where individuals may willingly give up their own reproductive future, or even their lives, for the good of the group.

According to Hölldobler, the “nested tug-of-war” idea got its start when he and Reeve were thinking about certain primitive ant species that don’t fit the selfless ant stereotype. They live in small colonies, and individual selection is still very much in play. Nobody gives up reproductive rights for the good of the group. They also communicate poorly and disagree about who does the chores. (Sound familiar?)

So how did other ant species evolve from this chaotic start to the point that millions of selfless individuals in a colony can live together in almost perfect harmony? Wilson emphasizes group selection. Reeve and Hölldobler argue that it’s still about individual selection and kin selection. But the group gradually became more important because of ecological pressure, in the form of patchy resources and fierce competition from rival colonies. And the tug-of-war for individual advantage within the group gave way to cooperative behaviors as the tug-of-war for advantage against rival groups became more pressing.

So let’s say this is true of people, too. The disturbing implication of the “nested tug-of-war” idea is that altruism is a byproduct of enmity: It’s easier to give up what we want, to sacrifice for a sister or a cousin, if we feel threatened by some outside group. And a long evolutionary history of living with that sort of threat is also why we still slip so easily into rivalries against other high schools, or political parties, or ethnic groups.

Knowing this “doesn’t justify anything,” says Hölldobler. “But if children understand that there is this trait, and it was adaptive in the past, but it’s not very adaptive now,” they can work around the impulse to engage in pointless group rivalries and cultivate altruism in less antagonistic contexts. On the other hand, he admits, we might not enjoy football games as much.

Or political campaigns. In the aftermath of the 2000 presidential election, according to Kristin Gore in The Times Magazine interview, Republicans bussed in protesters to stand outside the vice presidential mansion and scream, “Get out of Cheney’s house.” The Gore family apparently managed to refrain from “turning up the stereo to drown out the chants,” Noriega-fashion. But being under siege by the rival group no doubt re-kindled the family’s sense of unity and muted any hint of a tug-of-war within.

Call me a romantic, but I like to imagine the three sisters getting up together and going to the windows to brandish their delicate wrists, causing the horrified barbarians outside to flee in howling panic back under the rocks from which they had apparently crawled.