The wild relatives of chickens, red jungle fowl are promiscuous lovers. Since the jungle fowl stay close to home throughout their lives, sex can up the chances of mating with close relatives and delivering inbred offspring. Resisting incest can be difficult for the female fowl, which is dwarfed by the aggressive, sex-crazed males. To avoid the ill effects of brotherly love, the females store the male's sperm, and only after copulating does she somehow choose which sperm fertilizes her eggs.