"The two then looked at tendencies to accumulate mutations, to see if natural selection puts more or less pressure on genes that are specific to men or women. That is, to what extent are harmful mutations weeded out or tolerated in the population? Indeed, the researchers found that the efficiency of selection is weaker in many such genes. 'The more a gene was specific to one sex, the less selection we saw on the gene. And one more difference: This selection was even weaker wi ... th men,' says Gershoni.

Although they do not have a complete explanation for this additional difference, the researchers point to a theory of sexual evolution first proposed in the 1930s: 'In many species, females can produce only a limited number of offspring while males can, theoretically, father many more; so the species' survival will depend on more viable females in the population than males,' explains Pietrokovski. 'Thus natural selection can be more 'lax' with the genes that are only harmful to males.'" cocktail wears in navy blue