Researchers found that attractive women have more children than their less attractive counterparts and that a higher proportion of those children are female. Once those daughters become adult they tend to be good looking themselves and so the pattern is repeated as women over the generations become steadily more aesthetically pleasing.
As attractive couples are less likely to have boy than a girl, men, in contrast, remain as aesthetically unappealing as their caveman ancestors, the scientists claim. The findings have emerged from a series of studies of physical attractiveness and its links to reproductive success in humans. In a study released last week, Markus Jokela, a researcher at the University of Helsinki, found beautiful women had up to 16 per cent more children than less attractive women.
He looked at a sample of more than 2,000 men and women in America, following them through four decades of life. Their attractiveness was assessed from photographs taken during the study, which also collected data on the number of children they had.
A study in 2006 by scientists at the London School of Economics found that good-looking parents were far more likely to conceive daughters. He suggested this was because of differing "evolutionary strategies" that each sex has adopted to survive, and which had been subtly programmed into their DNA.
Mr Kanazawa said: "Physical attractiveness is a highly heritable trait, which disproportionately increases the reproductive success of daughters much more than that of sons. "If more attractive parents have more daughters and if physical attractiveness is heritable, it logically follows that women over many generations gradually become more physically attractive on average than men."