Extended female sexuality is where the female of a species mates when infertile. In most species, the female only engages in copulation when she is fertile. However, extended sexuality has been documented in old world primates, pair bonded birds and some insects (such as carrion beetles). Extended sexuality is most prominent in human females who exhibit no change in copulation rate across the ovarian cycle. Although this behaviour incurs costs to females, such as energy and time, many researchers have proposed reasons for its existence. These hypotheses include the male assistance hypothesis, which proposes that females gain non-genetic benefits (such as food and shelter) in exchange for sexual access. A sub-hypothesis of this is Hrdy's; proposing extended female sexuality as an adaptive p