Being a hominid in the late Pleistocene era (125,000 to 10,000 years ago) was a rough gig. In addition to hunting, gathering, and evolving, our ancestors had to deal with a fickle climate. The planet’s mean temperature varied over a range of about 46 degrees Fahrenheit, forcing hominid groups to wander far and wide in search of kinder climes and better grub. As these groups spread over the face of the Earth, they often bumped into each other – to violent effect: Conflicts between early human groups claimed up to 10 times more lives (as a percentage of all deaths) than did the European wars of the 20th century.
Yet groups whose members managed to coordinate among themselves to aggress against outsiders at least won more food and territory, suggest economists Jung-Kyoo Choi and Samuel Bowles in the Oct. 26, 2007, issue of Science. Having more food and territory, in turn, meant birthing more hominids with the same cooperative, yet xenophobic ways. And so over time, altruism – benefiting fellow group members at a personal cost – and parochialism – harboring hostilities toward members of other groups – evolved alongside each other, “with war as both the engine of this co-evolutionary process and its legacy,” writes Holly Arrow, a University of Oregon psychologist who commented on the research in the same issue of Science.
In other words, “we may have become good-natured precisely because of our warlike nature, and we may have become warlike because of our generous nature,” says Bowles, an economist at the Santa Fe Institute and the University of Siena.
Neither altruism nor parochialism alone makes much evolutionary sense. Altruists sacrifice their own genetic legacy to safeguard the reproduction of others – a Darwinian no-no. And parochials endanger themselves to spite others – also a needless risk. Yet combined, the authors write, altruism and parochialism yield creatures who are “willing to engage in hostile conflict with outsiders on behalf of their fellow group members,” and thereby increase the reproductive success of the entire group – a Darwinian win.
To test this idea, Choi and Bowles used computer simulations that modeled the behavior of small groups of hominid-like “agents” over thousands of generations. Each agent was either altruistic or stingy, as well as either parochial or tolerant. The authors found that over time, agents who were both altruistic and parochial dominated the groups. Likewise, they suggest, parochial altruists dominated – and then defined – our own species.
Although simulations like these mimic genetic transmission, Bowles’ team has not identified a gene for parochial altruism. “We’re not genetically racist or warlike,” he quickly points out. “We’re not doomed to warfare and hostility towards outside groups” – partly because we are able to identify with larger and larger groups of people.
“Look at American nationalism,” he continues. “Immigrants from all over the world pour into the United States, and within two generations, they are all willing to die for each other, for their fellow Americans.” And when parochial altruism evolved, he adds, conflict “didn’t have to do with race or religion. It had to do with the guys from the next valley.”
But by the same token, “you can create racial tensions out of almost nothing,” he says, noting how easily politicians created and then manipulated ethnocentric sentiments after the fall of the former Soviet Union and the former Yugoslavia. “It is very easy for group boundaries to become a matter of contest.”
To reduce intolerance, “people should take altruism more seriously as a very important human motivation,” says Bowles. “In designing public policies, we should not confine ourselves to trying to mobilize self-interest motives. Economists believe that you should mobilize selfish motives for public ends. But our findings suggest that altruistic motives should also be affirmed.” War may be our predecessors’ legacy, says Bowles, “but it need not be our future.”
Read more stories by Alana Conner.