ATTRACTIVE women are easier to find than handsome men because beautiful parents are more likely to have daughters than sons, a study has shown.

As time goes on, the beauty gap between men and women is expected to grow, the findings suggest. Women should go on becoming more attractive than men.

Researchers demonstrated that beautiful people are 36 per cent more likely to have a daughter than a son as their first-born child.

The discovery supports the evolutionary theory that parents tend to produce children who benefit from their own attributes.

Selection pressure means when parents have traits they can pass on that are better for boys than for girls, they are more likely to have boys.

Such traits include large size, strength and aggression, which might help a man compete for mates.

On the other hand, parents with heritable traits that are more advantageous to girls are more likely to have daughters.

Study leader Satoshi Kanazawa, an evolutionary psychologist at the London School of Economics, said: "Physical attractiveness is good for both men and women, but it is much better for women than for men. So physically attractive parents bias their offspring sex ratio to have more daughters."

Dr Kanazawa based his conclusions on data from 3000 Americans taking part in an investigation called the National Longitudinal Study of Adolescent Health.

When Dr Kanazawa looked at the sex of the volunteers' first-born children, he found attractive parents were far more likely to have had girls.

The findings were reported in the Journal of Theoretical Biology, published by Elsevier.

Dr Kanazawa said: "Because physical attractiveness is heritable, and because physically attractive parents have more daughters and less attractive parents have more sons, over time, the average level of physical attractiveness among women increases relative to men, so that women are, on average, more attractive than men."

People from all societies agree on who is beautiful and who is ugly, he stressed.

Previous research by Dr Kanazawa has shown scientists, mathematicians and engineers, who have systematic "male brains", are more likely to have sons than daughters. The same was true for big and tall parents, and violent fathers.

Conversely, nurses, social workers and kindergarten teachers with empathic "female brains" had more daughters. (News.com.au, enviado por Cisco Costa)