NewScientist.com news service
Chimps happily help out unrelated chimps and unfamiliar humans, even if it means exerting themselves for no reward, a new study shows.
True altruism - unselfish acts for another's benefit - was until recently considered uniquely human. Usually when animals cooperate, they either help relatives - thereby increasing chances of passing shared genes to the next generation - or they count on having favours returned in the future.
Now Felix Warneken and colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have found that 12 out of 18 semi-wild chimpanzees went out of their way to help an unfamiliar human who was struggling to reach a stick. Watch a video of a chimp helping retrieve the stick.
The primates did this even when they were inconvenienced - such as when they first had to climb into a 2.5-metre-high ropeway - and for no reward. Equivalent experiments with human toddlers gave similar results.
In a previous study, the same team observed similar hints of altruism in captive-raised chimps towards a familiar human.
"This is the first evidence of chimpanzees helping somebody they don't know," Warneken says, though he accepts that the chimps may have helped because they generally associate humans with rewards. "But we also found they helped other chimps."
In the latter experiment, the team taught the apes to remotely unchain a door. When the chimps then saw another, unrelated, chimp trying to open the door, they released the chain more often than when their peer was not actively trying to get in. They chose to help the other chimp achieve its goal, Warneken suggests. Watch a video of a chimp opening the door.
Primatologist Joan Silk at the University of California in Los Angeles, US, is intrigued because in previous studies unrelated chimps have not helped each other (see Friendship runs shallow in captive chimps ).
Warneken says apes in those experiments were obtaining their own food, and were not aware that other chimps needed help. "They were in a completely different mindset," he suggests.
But Silk thinks the difference might be the experimental animals themselves: "We should test the chimps from [Warneken's] study with the previous experiments," she says, to see if those chimps still appear altruistic.
Apes may show spontaneous altruism more readily when freed of the constraints of life in the wild, says Frans de Waal of Emory University in Atlanta, Georgia, US. He recalls young captive chimps helping an arthritic older female to climb a frame, and a male bonobo alerting zookeepers to drowning youngsters.
"Animals don't know much about genetic kinship or future return favours," de Waal says, arguing that altruism could still be a self-serving trait, helping to win the "altruist" a good reputation and higher status.
"Natural selection has produced psychological mechanisms designed to produce spontaneous helping that - on average and in the long run - works to the advantage of both actors and recipients."
The details of such mechanisms need teasing out, but empathy may lie behind such altruism. Warneken says the unimportance of rewards in his study suggests the chimps acted out of genuine concern for others.
Journal reference: PLoS Biology (DOI:10.1371/journal. pbio.0050184)