Cruel to be kind

1. Would you let another driver into your lane in heavy traffic? Or arc you the sort of driver who slows to a crawl when someone is tailgating or driving much too close behind you? If you do either, it’s OK: you're only being human.

2. To date, no evidence either of altruism or spite has been found in any other animal except Homo sapiens. Being nice or nasty at a cost to you reel f could be part of what makes you human. But now scientists arc investigating our closest genetic relative, the chimpanzee. Somewhere in the 99.7 per cent of DNA that the two species share, perhaps there are genes for charity and malice.

3. In a study carried out at Germany's Max Planck Institute for Evolutionary Anthropology, which was published in the British journal Proceedings of the Royal Society in 2006, researchers tested whether chimpanzees would help or hinder a hungry neighbour. A chimpanzee in a testing room had two choices: it could either deliver food to a chimpanzee in a room next door, or to an empty room. In both cases, the chimpanzee controlling the food could not get any itself. The study found the chimpanzee controlling the food would do nothing for half the time, then give food to the other chimpanzee only a quarter of the time - which demonstrates neither altruism nor spite. 'I was predicting chimps would be spiteful; says Keith Jensen, a doctoral student who led the study. 'I mean, they're chimpanzees. I get spat on all the time. But though they knew they couldn’t get the food, sometimes they gave it to the other guy anyway.'

4. In contrast, humans frequently perform selfless acts. We donate blood, give money to charities and help old ladies cross the street. Altruism is among the very foundations of our society. Banking, government, and health services all depend on people working for the benefit of complete strangers.

5. And we can be spiteful too. In the famous Ultimatum Game, $10 is to be shared by two people. Person 1 decides how the $10 is to be split between them, and Person 2 chooses to accept or reject the offer. If the offer is rejected, neither gets anything. Economists predicted Person 1 would offer a $9/$l split and that Person 2 would accept it because $1 is better than nothing. Surprisingly, Person 1 generally offers a kind and fair S5/S5 split, which is accepted. If anything less even is offered, Person 2 generally rejects the offer, docking their own pay as punishment for the other person's selfishness.

6. What happens if chimpanzees are rewarded? In a similar study published in Nature in October 2005, the chimpanzee controlling the food received food regardless of whether or not it chose to deliver food to a neighbour or an empty room. Again, the chimpanzee in control gave food to the neighbour only about a quarter of the time - even when the other chimpanzee was begging frantically.

7. I am able to help others at no cost to themselves, most humans will do so. This is called 'other-regarding', which means humans are considerate to each other. Chimps, it seems, are not. ‘I don’t know why chimps are not other-regarding/ says Joan Silk from the University of California at Los Angeles, who led the study. 'It might be they are unaware of others' needs. It might be they are aware, but unconcerned: The findings may come as a surprise to field primatologists who often observe chimpanzees sharing food in the wild, even precious sources of protein like meat. 'Food sharing among adults in the wild might be based on self-interest; says Silk. 'Males might share meat with other males because they anticipate receiving meat in return in the future. Alternatively, males might share meat because it is more costly to monopolise it than to allow others to share it.’

8. But for now it appears humans are the only animals known to think considerately and inconsiderately about others even when they are strangers. Chimpanzees do not appear to have either the ability or the inclination. Perhaps somewhere along the split with our common ancestor, the selfless gene and the mean gene evolved.

9. So next time someone cuts into your lane, relax - it's higher evolution at work.