The success of this research may lie in the fact that selection was carried out over multiple generations, which increased the likelihood of identifying small genetic effects. Some problems remain, however. For instance, the scientists cannot distinguish between the effects of female choice and male competition in the "M" lines. Still, the most important finding is the confirmation that adult survival rates increased in populations with an increased opportunity for sexual selection. The result is consistent with the idea that females choose males on the basis of relatively high genetic quality. It was clear that enforced monogamy was bad news for the "S" lines of flies. A family reunion would be a much busier affair for the offspring of females who could be choosy.
The research opens some new doors for investigation though much remains unknown. Promislow said that not all fitness traits necessarily will benefit from sexual selection and that gene-environment interactions could create unexpected consequences generations down the line. And genetic benefits to one sex may even prove detrimental to the other.
In the meantime, the current study confirms the validity of at least one model of sexual selection.
"We wanted to provide an explicit test of the 'good genes' model," said Promislow. "And we can say that what we found was consistent with that model and with others. But I don't think we will ever find one unifying model that explains the patterns of sexual selection in all organisms."