 The whiptail lizard ("A. uniparens"), presented an opportunity to study first-hand how the neuroendocrine substrates underlying sexual behavior can evolve.In this instance, Dr. Crews used a parthenogenetic species derived from interbreeding of two sexual species.Remarkably, although the descendant species consists only of females, reproducing by obligate parthenogenesis, individuals continue to display sexual behaviors that are typical of both females and males, alternating behaviors depending upon their individual hormone profiles across reproductive cycles.