Scientists have discovered a gene  that plays a role in violence  in men ill-treated in childhood.The discovery could explain why some experience unhappy childhoods and go on to normal lives, while others turn to violence, crime of antisocial deeds. But it will also restart another argument. Terrie Moffitt and Avshalom Caspi report in Science today that one common form of a gene in the brain makes men more likely to be violent--but only if they have experienced cruelty or rejection in childhood . The researchers followed up the life histories of 442 boys born in New Zealand in 1972. Of these, 154 had been ill-treated in the first 10 years, 33 of them badly. They had either experienced sexual attack, beatings or rejection by mother or stepparents. Of the 154 children , 55 had a less active variant  of a gene called MAOA, and 99 had the more active variant . The 55 boys were more than twice as likely to have been in trouble as the other ill-treated group . They made up 12% of the total, but were responsible for 44% of all crimes from among the 442 boys. Prof Moffitt thought a "violence" gene had not been discovered. Boys with the less active form who were not ill-treated during childhood lived normal lives. "It is very common in the population. One third of us have it." she said, "So the gene doesn't do much of anything, it doesn't cause any trouble in any way, unless we are also ill -treated". The gene might also show the ability to bear mental stress. The army or the police might examine the applicants  to see if they have the more active form . But the discovery also raises the argument that people with the less active form of the gene could be social dangers, to be treated with medicine. "This research can easily lead people to fix social problems through medical treatment," said David King of the UK Gene Alert Group. We can learn from the passage that those men who have stronger ability to bear mental stress usually_.
have the more active variant of gene have the less active variant of the gene had ill-treated childhood had no ill-treated childhood