June 26, 2007 The evolutionary roots of human altruism may go deeper than previously thought according to a report to be published in the Public Library of Science (PloS) Biology journal this week. It is often assumed that altruism is either unique to humans or else the human version differs from that of other animals in important ways - only humans are supposed to act on behalf of others without personal gain and at a cost to themselves – but new experimental evidence that chimpanzees act altruistically toward genetically unrelated members of the same species suggests that this psychological trait may not be unique to humans.

The experiments conducted by Felix Warneken and colleagues from the Max Planck Institute for Evolutionary Anthropology also found evidence that both chimpanzees and human infants helped altruistically regardless of any expectation of reward, even when some effort was required, and even when the recipient was an unfamiliar individual—all features previously thought not to apply to our closest living evolutionary relatives like the chimpanzee. The evolutionary roots of human altruism may thus go deeper than previously thought, reaching as far back as the last common ancestor of humans and chimpanzees.