At a smoky blackjack table in Monaco, a young man has gotten himself into a fix. He’s lost almost his entire savings, and now has a chance to go double or nothing. His friends crowd around the table, as do a few young women from the bar.

It is at this exact moment, say evolutionary psychologists Leda Cosmides and John Tooby, that eons of male decision-making habits kick in. According to their new study, Status and Risky Decision-Making, the presence of male peers would likely spur the gambler to bet the farm—a high-risk decision stemming from an ancestral drive to attain dominant social status and attract mates.

Cosmides and Tooby specialize in decoding the evolutionary imprint in human behavior. The husband–and–wife team met as doctoral students at Harvard and now co-direct the Center for Evolutionary Psychology at the University of California, Santa Barbara. Since helping to pioneer their field in the mid-1980s, they have studied such divergent topics as incest aversion and the origins of gift-giving.

Their latest study looks at the economic implications of dominance theory, a central concept in evolutionary psychology. The theory posits that humans evolved within hierarchical bands of hunter-gatherers: Social status determined which men had access to resources and, consequently, the best shot at attracting a mate. Even today, Cosmides and Tooby argue, resource decisions are made not in a bubble of rational self-interest, but in the context of constant competition for status. When it comes to money, does a man’s social status influence his tendency to take risks? If so, what context will spark the riskiest decisions?

To answer these questions, they set up two experiments, the results of which are published in the January 2008 issue of Evolution and Human Behavior. In the first, students from Franklin & Marshall College resolved a monetary problem while supposedly being observed by another student from a less, equally, or more prestigious college: a local community college, Franklin & Marshall, or Princeton. The subjects were asked to imagine that they had just lost $60 worth of stock, then given a choice between being paid a sure $25 and having a one-in-three chance of gaining $75. The results showed that men were twice as likely to pick the high-risk option when being observed by their peers as they were when being watched by males of higher or lower status. (Women showed no change in behavior either way.)

When the same experiment at UC Santa Barbara (which used imaginary Harvard students as the superior gauge) produced similar results, Cosmides and Tooby concluded that impending financial loss likely triggers competitive behavior and high-risk decisions, especially when a man is competing for advantage against his peers.The results suggest that evolutionary behavior can outlive its usefulness. In hunter-gatherer societies, it makes sense for men to gamble resources in order to gain status and attract women. But is a stockbroker well-served making a high-risk investment simply because he is trying to do better than his colleagues? Probably not. Cosmides argues that rational thought has nothing to do with it. “It’s like Playboy,” she says. “It makes no sense for men to be aroused by pieces of paper with pictures of women on them, but when it comes to sex, we’re motivated by ancestral cues.”