Orgasm men are capable of achieving them is supported by men who have reported having multiple, consecutive orgasms, particularly without ejaculation. Males who experience dry orgasms can often produce multiple orgasms, as the refractory period is reduced. An increased infusion of the hormone oxytocin during ejaculation is believed to be chiefly responsible for the refractory period, and the amount by which oxytocin is increased may affect the length of each refractory period. Another chemical which is considered to be responsible for the male refractory period is prolactin, which represses dopamine, which is responsible for sexual arousal. Because of this, there is
Social monogamy in mammalian species advantages, however, do not describe why monogamy, and not polygyny, has evolved in the species mentioned above. Some possible conditions which may account for cases of monogamous behavior in mammalian species may have to do with: There are several hypotheses for the evolution of mammalian monogamy that have been extensively studied. While some of these hypotheses apply to a majority of monogamous species, other apply to a very limited number of them. Vasopressin, a hormone that induces a male prairie vole ("Microtus ochrogasters") to mate with one female and stay by her side in order to protect her, has been