In mouse and fruit flies, researchers from the Prague Academy of Sciences and Rochester University have identified genes that prevent hybrid proliferation, respectively. Hybrids are those produced by crossing two different species, usually sterile. It is important to know which gene produces sterility from the evolutionary point of view of the species. In fact, these individuals do not advance and therefore evolution continues on another path. So far, however, few genes have been identified (taking into account the current ones, they do not reach the dozen), so from now on researchers have work.