UCSB researchers recently found an evolutionary link between political motivation and physical strength in males, where increased upper body size indicated a more aggressive and self-serving stance toward resource redistribution.

Daniel Sznycer, a postdoctoral researcher at UCSB’s Center for Evolutionary Psychology, Michael Bang Petersen of Aarhus University in Denmark and Aaron Sell of Griffith University in Australia collaborated with UCSB professors Leda Cosmides and John Tooby on the study. Their paper, “It’s there among invertebrates, vertebrates, non-human primates, and human primates — us,” is published in the May issue of the journal Psychological Science.

According to Sznycer, upper body strength determined males’ attitude toward redistribution, which involves a transfer of resources from wealthy to poor. Self-interest among these men varied with socioeconomic status.

“Specifically, we found that among people of high socioeconomic status — the ones who stand to lose from redistribution — superior physical strength was associated with increased opposition to redistributive policies,” Sznycer said. “In contrast, among people of low socioeconomic status — the ones who stand to gain from redistribution — higher strength had the opposite effect; it boosted the support for redistribution.”

The researchers measured upper body strength and support for income redistribution among men and women in Argentina, Denmark and the United States. Accounting for varying redistribution policies, the data collected from these countries showed that the same link existed across cultures but affected only men. These results suggest that the standard features of the human mind rather than cultural forces drive political motives.

Aaron Sell, co-author of the research paper, said that the incongruity between the environment of our ancestors and the conditions of modern society explain much of irrational human behavior.

“This means that if we want to know why some people vote the way that they do, we have to understand the brain and how it evolved,” Sell said. “It appears to have evolved so that men who are physically strong will pursue their own self-interest, while men who are physically weak will be prone to give in and surrender their own self-interest.”

Sznycer said that some adults’ inability to digest lactose and our preference for unhealthy foods are examples of the ongoing influence of our ancestors and that many evolutionary processes are slow to catch up with modern conditions.

“The available data suggest that variables relevant to our hunter-gatherer and mammalian ancestors still shape the contents of attitudes, tastes and sentiments, including political attitude, even when those variables are not relevant to how modern societies work,” Sznycer said. “It is not that cultural or social processes on the one hand and evolutionary processes on the other are mutually exclusive. Rather, the issue is whether natural selection had enough time to catch up with novel social or institutional environments to build an adaptive psychology.”

In the world of animal conflict, two main variables determine the likelihood of prevailing in a fight over resources: mainly, which competitor places higher value on the resource and which competitor has greater fighting ability.

Sznycer said that researchers also found that strength does not modulate women’s attitudes about redistribution because, historically, women are less likely to use physical aggression to obtain resources.

“This is consistent with the male bias in the aggressive use of force among mammals. Women can certainly be competitive, but they use more indirect forms of aggression,” Sznycer said. “The assertion of self-interest among women is driven by physical attractiveness more than physical strength.”

Sell said that public support for political positions in the modern world is a consequence of a brain that evolved in the past.

“This research explains why people’s political opinions are not predictable solely by self-interest. Many people in political science assume that people vote in their own self-interest. The data does not support this though.”


A version of this article appeared on page 5 of May 28, 2013′s print edition of The Daily Nexus.