Captive chimpanzees fail to help others in their social group, even when it causes no inconvenience, a behavioural study in Nature journal has found.
Chimpanzees show many humanlike attributes
Helpfulness is prevalent in humans, even when it may harm the helper's own interests to aid another.
Humanlike attributes shown by chimps include tool use and maybe rudimentary language skills, but this study suggests altruism is not among them.
But other researchers said that captive chimps may be less socially inclined.
A team led by Joan Silk of the University of California, Los Angeles (UCLA), set captive chimpanzees tests in which they obtained a food reward.
The chimps were presented with two reward options. One option allowed a chimp only to serve itself with food. The other secured the same reward, but also delivered food to another chimpanzee in an enclosure next door.
Dr Silk's team found the 29 chimps tested in the study were no more likely to pick the second option than the first, even though it allowed them to do a "good deed" at no cost to themselves.
The result was surprising because the chimps had been living together in the same group for 15 years. They were not related, but might have been expected to be very close.
Food sharing has been demonstrated in groups of wild chimpanzees. So the Nature study raises questions about how this behaviour arises.
Other researchers suggest that the result could be down to the unnatural situation or to differences in behaviour brought on by captivity.