A study led by Youcef Ouadah at the California Institute of Technology has found that male fruit flies from Drosophila santomea, which typically fight for the right to mate with a female, do not fight each other when placed together. Instead, they court each other through displays of physical beauty and prowess. Despite this, these fruit flies can distinguish males from females and reproduce normally. This strategy evolved independently more than once. The study also found that when the two species of fruit fly interbreed, females evolved a strong preference for mates of their own species.