http://www.nature.com/news/2008/080404/full/news.2008.738.html

Selfish dictators may owe their behaviour partly to their genes, according to a study that claims to have found a genetic link to ruthlessness. The study might help to explain the money-grabbing tendencies of those with a Machiavellian streak — from national dictators down to 'little Hitlers' found in workplaces the world over.

Researchers at the Hebrew University in Jerusalem found a link between a gene called AVPR1a and ruthless behaviour in an economic exercise called the 'Dictator Game'. The exercise allows players to behave selflessly, or like money-grabbing dictators such as former Zaire President Mobutu, who plundered the mineral wealth of his country to become one of the world's richest men while its citizens suffered in poverty.

Ebstein and his colleagues decided to look at AVPR1a because it is known to produce receptors in the brain that detect vasopressin, a hormone involved in altruism and 'prosocial' behaviour. Studies of prairie voles have previously shown that this hormone is important for binding together these rodents' tight-knit social groups.

Ebstein's team wondered whether differences in how this receptor is expressed in the human brain may make different people more or less likely to behave generously.

To find out, they tested DNA samples from more than 200 student volunteers, before asking the students to play the dictator game (volunteers were not told the name of the game, lest it influence their behaviour). Students were divided into two groups: 'dictators' and 'receivers' (called 'A' and 'B' to the participants). Each dictator was told that they would receive 50 shekels (worth about US$14), but were free to share as much or as little of this with a receiver, whom they would never have to meet. The receiver's fortunes thus depended entirely on the dictator's generosity.

About 18% of all dictators kept all of the money, Ebstein and his colleagues report in the journal Genes, Brain and Behavior 1. About one-third split the money down the middle, and a generous 6% gave the whole lot away.
Long and short

There was no connection between the participants' gender and their behaviour, the team reports. But there was a link to the length of the AVPR1a gene: people were more likely to behave selfishly the shorter their version of this gene.

It isn't clear how the length of AVPR1a affects vasopressin receptors: it is thought that rather than controlling the number of receptors, it may control where in the brain the receptors are distributed. Ebstein suggests the vasopressin receptors in the brains of people with short AVPR1a may be distributed in such a way to make them less likely to feel rewarded by the act of giving.

Though the mechanism is unclear, Ebstein says, he is fairly sure that selfish, greedy dictatorship has a genetic component. It would be easier to confirm this if history's infamous dictators conveniently had living identical twins, he says, so we could see if they were just as ruthless as each other.

Researchers should nevertheless be careful about using the relatively blunt tool of the Dictator Game to draw conclusions about human generosity, says Nicholas Bardsley at the University of Southampton, UK, who studies such games.

That certainly fits with the image of a naïve yet arrogant dictator with no sense of the inappropriateness of his actions and attitudes. Such figures have cropped up with surprising regularity throughout history, all the way from the emperors of Rome, through to Napoleon Bonaparte, Benito Mussolini, Saddam Hussein or Robert Mugabe, now tenaciously clinging to power in the face of uncertain electoral results.