In recent years scientists have been tumbling over each other to announce the discovery of disease-causing genes for breast cancer, colon cancer, Huntington's, bubble boy disease and so on. Once detected, disease-bearing embryos or foetuses can be treated or, more often, destroyed. Now researchers in Scotland claim to have found a "poverty gene" which causes people from deprived areas to age rapidly, be unhealthy and shirk work. They suspect that a hyperactive immune system floods the brain with chemicals which suppress a desire for self-advancement.

Faulty evolution is at work, apparently. An active immune system helps to keep children healthy, but in later life it causes additional stress on the body. "If you look at a person from the East End of Glasgow aged 55," says Dr Chris Packard, of the Glasgow Centre for Population Health, " they may look far closer to 65 or 70, while those from a more affluent area of the same age will probably be far closer to their real age."

Other experts have dismissed the news. Allyson Pollock, of the Centre for International Public Health Policy, warned that linking poverty to genetics could lead to the notion that the poor were inferior. "Poverty is not a genetic issue, it is an economic issue," she said. "If you go down that route you may end up with eugenics, and that is extremely worrying."