Intelligent men owe their brains to their mothers, according to research published today in The Lancet.
Growing evidence shows that several genes which determine intelligence appear to be located on the X chromosome, the one men inherit from their mothers .Any mutation on the X chromosome has more effect on a man than a woman because a woman inherits X chromosomes from both her parents, which tends to dilute the gene's impact.
But a man only has one X chromosome inherited from his mother, which is paired with the much smaller Y chromosomes from his father. Therefore, an intelligence-enhancing X gene has more of a chance of becoming the predominate gene, determining the man's basic intelligence, looks and character. It also works the other way; if the predominate gene is not as strong as it should be, the man is more likely to suffer mental retardation.
Professor Gillian Turner, the author of the study, said: "If the gene is the one that increases intelligence then its full effect will be seen in men, while in women the benefit is less pronounced. This explains why some men are extraordinarily intelligent." She concludes that if a man wants smart sons his best bet is to marry a smart woman.