Science Daily has a summary of new fly research in behavioral genetics which puts the spotlight on deep time evolutionary dynamics. Here's the important bit:
The researchers found that when the fruit fly larvae were competing for food, those that did best had a version of the foraging gene that was rarest in a particular population. For example, rovers did better when there were lots of sitters, and sitters did better when there were more rovers.
In short the researchers here are pointing to negative frequency dependent selection, where traits/alleles exhibit a fitness as an inverse function of their frequency. This shouldn't be a surprise, the MHC loci are extremely polymorphic likely due in large part to frequency dependent effects. These genes are critical within the adaptive immune system of many "higher" organisms, an major line of defense against pathogens. Since pathogens evolve so quickly they can usually outfox common ...
