FEMALE PERPLEXITY about the purpose of men may have been solved by an experiment that has shown how males are a vital ingredient of evolution.
Biologists have long puzzled over the function of males and why sex is so common in the animal world, given that it appears to be disadvantageous for females to practise it. If females went in for asexual reproduction, they would produce twice as many offspring who would all share the mother's genes.
In simple mathematical terms, sex makes no sense and the production of males - who frequently contribute little to rearing offspring - seems to be a waste of valuable resources.
The latest study, involving the ubiquitous fruit fly, offers a possible explanation for the role of the male in ridding harmful mutations from the gene pool and increasing the number of beneficial traits.
William Rice and Adam Chippindale, biologists from the University of California, Santa Barbara, found that the rate of "progressive evolution", where beneficial traits accumulated, was faster in populations of flies that reproduced sexually compared with those forced into asexual reproduction.
The disadvantages of sex applied to males as well as females because being a father carried huge costs, Dr Rice said. "My son only has half my genes; the other half are from his mother. Only half of my genome is getting into the population," he said.
"However, if I were an asexual female, my offspring would carry all of my genome. …