User:FatimahB/Social monogamy in mammalian species

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Social monogamy is defined as sexually mature adult organisms living in pairs. While there are many definitions of social monogamy, this social organization can be found in invertebrates, reptiles and amphibians, fish, birds, mammals, and humans. It is possible for a species to be both genetically monogamous and socially monogamous but it is more likely for species to practice social monogamy and not genetic monogamy.

Some socially monogamous species exhibit pair bonds that occur between two sexually mature organisms, have an affective component, be specific to the individual, last longer that one reproductive cycle, and be quantifiable in strength or quality of relationship. Pair bonding can exhibit (but does not have to) sexual behaviors and/or bi-parental care. Pair bonding cannot exhibit, however, organisms that cannot identify one another in a pair, end in the death of a mate or separation from the mate directly after mating, lack of distress when separated from the mate, or lack sociality. Not all socially monogamous species exhibit pair bonding, but all pair bonding animals practice social monogamy. These characteristics aid in identifying a species as being socially monogamous.

At the biological level, social monogamy affects the neurobiology of the organism through hormone pathways such as vasopressin and oxytocin. Vasopressin is related to the distress hormone an organism feels when separated from their mate while oxytocin is associated with the affective component of the social interactions between mates. These biological factors give way to a genetic component that evolution could act on via selection to evolve social monogamy in animals.

Mate guarding
One hypothesis regarding the evolution of social monogamy in mammals is in regard to mate guarding and specifically relates to species where social monogamy is present, yet bi-parental care is not.

Partner scarcity
Another hypothesis asserts that partner availability is a key factor in the evolution of social monogamy in mammals.