Taking advantage of the availability of hundreds of completely sequenced genomes both from humans and flies, we did the first comparison of the intraspecies variation of genes with their interspecies variation . We find that in the set of genes highly conserved between flies and humans, there are outliers that are highly variable within the datasets studied. These genes are enriched in ribosomal proteins, which are different ones for humans and flies. Hijacking of the ribosomal machinery by viruses is needed for their infectivity. Therefore, we interprete this result as a signal of evolutionary pressure in populations to increase the variability of proteins (likely in loops not affecting functionality) to avoid recognition by viruses. Variability of these proteins within a species would make difficult for the virus to infect many members of the population.
 Shih, J., R. Hodge and M.A. Andrade-Navarro. 2014. Comparison of inter and intraspecies variation in humans and fruit flies. Genomics Data. 3, 49-54.