 Neoteny of the genitals is marked by the absence of a baculum (penis bone); the presence of a hymen; and the forward-facing vagina.Neoteny in humans is further indicated by the limbs and body posture, with the limbs proportionately short compared to torso length; longer leg than arm length; the structure of the foot; and the upright stance.Humans also retain a plasticity of behavior that is generally found among animals only in the young.