The implications are that females select their partners on the basis of whether they have strong genes.

The research involves the humble fruit fly, but experts believe it could have implications for the human mating game.

Geneticists from the University of Georgia, led by Dr Daniel Promislow, put one virgin Drosophila melanogaster, a variety of fruit fly, in a vial with one virgin female.

No sex

Some of the females refused to mate altogether, despite the fact that fruit flies are renowned for their propensity for mating almost any time, any place.

The scientists also put some females in vials with five males so that female choice and male competition could come into play.

Female fruit flies preferred to pick their mates

The experiment was carried out on fruit flies of a wide variety of age groups.

The scientists measured offspring in terms of their survivability, their wing size, asymmetry of features and the number of tooths on their sex combs which are used to sense females.

The main difference between offspring was that those whose mothers had been able to pick their mate were more likely to live longer.

Adult survival

"We know there are fitness consequences to sexual selection, but past studies have largely focused on juvenile survival [ie, survival just after birth]," said Dr Promislow.

"Our results focus on adults, and we showed that the process of sexual selection can lead to a genetically related increase in the components of adult fitness."

The research, published in the Proceedings of the National Academy of Sciences, is partially supported by the US National Institute on Aging.

Survival of the fittest

But there is good news for those who have drawn the short straw in the survival of the fittest race: scientists acknowledge that sexual selection may not have a positive effect on all aspects of fitness.

Dr Promislow also admitted that the mating game will probably never be totally understood in scientific terms.