The mean gene that makes people stingy

If you have a friend who never buys a round or who rarely pays their fair share, try not to get too angry.

Because being mean could be in their genes. Scientists have pinpointed a stretch of DNA that makes people stingy with their cash, the Daily Mail reported.

Around one in four of us carries the 'mean gene', which we have inherited from our parents.

In the study, those with the gene gave less money to charity than others.

Such thrifty sorts may also constantly cadge cigarettes, rather than buying their own, or regularly borrow cash for bus fares, but rarely pay it back.

Keen to look out for themselves - and their cash - they may also insist on totting up every item of food they have eaten in a restaurant, rather than simply splitting the bill equally.

The German researchers took samples of cells from inside the mouths of 101 young men and women and tested them for a gene called Comt.

The gene, which comes in 'G' and 'A' versions, is known to influence brain chemistry and the researchers believed it may do so in a way that affects how generous - or not - we are towards others.

The volunteers were given a gambling computer game to play and then told they could donate some or all of their winnings to a poor child in Peru.

To tug the heart strings, they were shown a picture of a girl called Lina and a bracelet that she had knitted.

The type of Comt gene did not affect how much the men and women won on the gambling game - but it did affect how much they gave to charity.

More than 20 per cent of those with the 'G' version gave all the cash they had won to Lina, but fewer than 2 per cent with the 'A' version were as generous.

On average, those with the 'A' version, or the 'mean gene' gave less than half as much to charity, the University of Bonn study found. But tight wads can't entirely blame their DNA.

Previous research has shown that our propensity towards generosity is only partly explained by our genes.

This means that other factors, such as upbringing, education and religion also play a role.

Spendthrifts, however, don't necessarily have the moral high ground. It is thought that one of the reasons we splash our cash or help others is simply because it makes us feel good.

Writing in the journal Social Cognitive and Affective Neuroscience, the researcher said: "Altruism is defined as a selfless concern for the welfare of others.

"However, there is a great debate in the literature if true altruism really exists. People who doubt the existence of pure altruism argue that helping others is intrinsically rewarding and therefore they are exercising their personal interest to benefit their own selves rather than others."

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