Chimpanzees, in a test of their willingness to share with other chimps, displayed a surprising sense of fairness, scientists say, debunking the idea that only humans boast the quality.
The US researchers said they are the first to show chimpanzees have a sense of fairness and that it may have evolved over time to aid their survival.
The experiments were carried out by scientists at the Yerkes National Primate Research Centre at Emory University near Atlanta, Georgia, working with colleagues at Georgia State University.
They taught the chimps to play a game dubbed "ultimatum" in which "one individual needs to propose a reward division to another individual, and then have that individual accept the proposition before both can obtain the rewards", said researcher Frans de Waal.
Researchers ran the test separately on six adult chimpanzees and 20 human children between the ages of two and seven.
The game was simple: one individual chose between two differently coloured tokens that, with his or her partner's co-operation, could be exchanged for rewards; a snack for the chimps, or stickers for the children.
A token of one colour offered equal rewards to both players, while the other gave the individual making the choice a much larger share of the spoils. The results showed no differences between human and chimp behaviour: if the partner's co-operation was required, the chimps and children split the rewards equally, researchers said.
"Humans typically offer generous portions, such as 50 per cent of the reward, to their partners, and that's exactly what we recorded in our study with chimpanzees," said de Waal.
The researchers noted, however, that when they modified the rules so that a partner had no chance to refuse the offer, both the chimpanzees and the children chose the selfish option.