Dysphoric milk ejection reflex to nipple/areolar stimulation, thoughts of the baby or of breastfeeding, or overfull breasts, travels through both brain and bloodstream, causing emotional changes in the brain and the release of milk in the breast. Prolactin, released in a gradual wave that peaks after the beginning of a feeding, is responsible for continued milk production. Dopamine inhibits the release of prolactin, so dopamine levels must drop in order for prolactin levels to rise. Some speculate that the necessary dopamine drop is similar to (and timed with) the oxytocin spike – a sort of negative image – but that in D-MER mothers it
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