<unk>  is where the<unk>  of a species mates despite being infertile. In most species, the<unk>  only engages in copulation when she is fertile. However,<unk><unk>  has been documented in old world primates, pair bonded birds and some insects (such as carrion beetles).<unk><unk>  is most prominent in human<unk> s who exhibit no change in copulation rate across the ovarian cycle. Although this behaviour incurs costs to<unk> s, such as energy and time, many researchers have proposed reasons for its existence. These hypotheses include the male assistance hypothesis, which proposes that<unk> s gain non-genetic benefits (such as food and shelter) in exchange for sexual access. A sub-hypothesis of this is Hrdy's, proposing<unk>  as an adaptive process aiming to creating paternity confusion in males. Alternative hypotheses, classified as 'male-driven', claim that<unk>  occurs due to male adaptations, resulting from an inability to detect fertility status in<unk> s or to dampen immune responses against sperm. Finally, Spuhler's hypothesis suggests that the behaviour may have arisen as an incidental effect of larger adrenal glands in humans. The human menstrual cycle
Extended female sexuality
Sexual addiction
Sexually active life expectancy
Gender dysphoria
Sexual relationship disorder
Persistent genital arousal disorder
Prison sexuality
Gender dysphoria in children