 testis in primate lineages.In "C. elegans", which is an androdioecious species (a population consisting of only hermaphrodites and males), the rate of evolution for genes expressed during spermatogenesis was higher in males than in hermaphrodites.In "Drosophila", interspecies divergence was found to be higher than intraspecific polymorphism at non synonymous sites of male biased genes which elucidated the role of positive selection and showed that male biased genes undergo frequent adaptive evolution.