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Updated 10:00 AM July 24, 2006




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New theory: Selfish genes make humans selfless

Humans are altruistic by nature, according to a new theory published in the current issue of Psychological Inquiry.

The theory focuses on explaining the kind of altruistic behavior that involves costly long-term investment in others, such as parenting, caring for the sick or injured, and protecting family and comrades in times of conflict or war. This behavior typically entails considerable sacrifice—of time, effort, health, and even life itself.

"Considering the self-centered motives that are evolutionarily ancient and that continue to drive human behavior today, it's worth considering why people make these kinds of sacrifices," says U-M psychologist Stephanie L. Brown, who developed the new theory in collaboration with her father, Michael Brown, a psychology professor at Pacific Lutheran University.

Brown and Brown argue that the social bond—the glue of close interpersonal relationships—evolved to discount the risks of engaging in high-cost altruism. They propose that social bonds override self-interest and motivate costly investment in others. The formation of social bonds must have occurred mainly between individuals who were dependent upon one another for reproductive success, or whose evolutionary fates were linked.

"This linkage would have provided givers with a genetic safety net, making them resistant to exploitation," says Brown, an assistant professor of general medicine at the Medical School and a faculty associate at the Institute for Social Research (ISR), affiliated with the ISR Evolution and Human Adaptation Program.

Effectively, the selective investment theory presents a striking alternative to traditional self-interest theories of close relationships that tend to emphasize what individuals get from others, not what they give.

"Viewed through the lens of selective investment theory," Brown says, "the fabric of close relationships appears different. Sacrifice becomes a characteristic feature of healthy, enduring relationships rather than aberrant, inexplicable, or diagnostic of pathology"

What makes selective investment theory distinctive not only is its focus on high-cost altruism, but also its premise that "selfish genes" ultimately are responsible for selfless, other-directed behavior.

"Selfish genes can produce selfless humans," says Brown, explaining that high-cost altruism helped insure the survival, growth and reproduction of increasingly interdependent members of ancestral hunter-gatherer groups.

"Viewed in this way, the spread of altruism in humans is no surprise," she says. "Even altruism directed to genetically unrelated individuals is not as mysterious as some have supposed."

In support of their theory, Brown and Brown cite evidence from a wide range of fields, including neuroendocrinology, ethology and behavioral ecology, and relationship science.

"The same hormones that underlie social bonds and affiliation, such as oxytocin, also stimulate giving behavior under conditions of interdependence," Brown says.

The Browns say their theory has important implications for relationship science. "We do not deny that close relationships involve selfish motivation," says Stephanie Brown, "but the picture may be more complex. If social bonds evolved to support altruism then we may need to re-think the way we view human sociality. Models of psychological hedonism and rational self-interest may need to be expanded in order to describe our behaviors in families, at work and even on the national stage."

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