Source: Science Daily

Imagine you’re dining at a restaurant in a city you’re visiting for the first — and, most likely the last — time. Chances are slim to none that you’ll ever see your server again, so if you wanted to shave a few dollars off your tab by not leaving a tip, you could do so. And yet, if you’re like most people, you will leave the tip anyway, and not give it another thought.

These commonplace acts of generosity — where no future return is likely — have long posed a scientific puzzle to evolutionary biologists and economists. In acting generously, the donor incurs a cost to benefit someone else. But choosing to incur a cost with no prospect of a compensating benefit is seen as maladaptive by biologists and irrational by economists. If traditional theories in these fields are true, such behaviors should have been weeded out long ago by evolution or by self-interest. According to these theories, human nature is fundamentally self-serving, with any “excess” generosity the result of social pressure or cultural conformity.

Recently, however, a team of scientists at UC Santa Barbara conducted a series of computer simulations designed to test whether it was really true that evolution would select against generosity in situations where there is no future payoff. Their work surprisingly shows that generosity — acting to help others in the absence of foreseeable gains — emerges naturally from the evolution of cooperation. This means that human generosity is likely to rest on more than social pressure, and is instead built in to human nature.

Their findings appear in the current issue of the Proceedings of the National Academy of Sciences.

“When past researchers carefully measured people’s choices, they found that people all over the world were more generous than the reigning theories of economics and biology predicted they should be,” said Max M. Krasnow, a postdoctoral scholar at UCSB’s Center for Evolutionary Psychology, and one of the paper’s lead authors. “Even when people believe the interaction to be one-time only, they are often generous to the person they are interacting with.”

“Our simulations explain that the reason people are more generous than economic and biological theory would predict is due to the inherent uncertainty of social life,” added Andrew Delton, also a postdoctoral scholar at the Center for Evolutionary Psychology and the paper’s other lead author. “Specifically, you can never know for certain whether an interaction you are having right now will be one-time only — like interacting with a server in a distant city — or continue on indefinitely — like interacting with a server at your favorite hometown diner.”

Krasnow and Delton co-authored the paper with Leda Cosmides, professor of psychology and co-director of the Center for Evolutionary Psychology; and John Tooby, professor of anthropology and also co-director of the Center for Evolutionary Psychology.

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