This kind of aggressive, anti-social behaviour is more likely to be inherited than non-aggressive naughtiness like truancy, stealing and lying.

Dr Jim Stephenson explains the results of the study

Whereas only 30-40% of the differences in the twins' non-aggressive anti-social behaviour could be put down to genes, the figures for bullying and fighting were much higher.

But one of the research team, Dr Jim Stephenson at Southampton University told the BBC: "We don't see genes as determining behaviour. We suggest there are genes that contribute toward a liability to be more aggressive.

"That doesn't mean you are a victim of those genes. What any child has to do is deal with the biological load that they have and regulate their behaviour."

Genetic future

The study raises again the complex ethical issue of what use should be made of genetic information which may indicate likely future behaviour or health.

Asked if schools in future might ask to see the results of genetic tests before accepting a child, Dr Stephenson said: "Yes, they may want to see their DNA gels, which would be a horrendous situation. But I'm not in a privileged position to give a view on that because it is a broader social issue."

"Society as a whole has to deal with the way it lives with what's becoming known as the 'post-genome' situation, where these markers of risk are known."

Nature versus nurture

The competing influences of nature versus nurture can be teased out in studies like this one because some twins are identical and some are not.

Identical twins have identical DNA profiles, those who are not share about half of their genes. Looking at the different behaviours shown by the two types of twin means the influence of environment can be separated from genetic inheritance.

The study was done by scientists at Southampton University, the Institute of Psychiatry in London and the Karolinska Institute, Sweden.

It showed that for non-aggressive anti-social behaviour, boys were influenced mostly by their environment but girls were affected most by their genes.

It was relatively common for a child to show both aggressive and non-aggressive bad behaviour, rather than just one type. Again, boys seemed to get this from environmental factors, girls from their genes.