Mate for life

In biology, a pair bond is the strong affinity that develops in some species between a pair consisting of a male and female, or in some cases as a same-sex pairing, potentially leading to producing offspring and/or a lifelong bond. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary biology circles. The term often implies either a lifelong socially monogamous relationship or a stage of mating interaction in socially monogamous species. It is sometimes used in reference to human relationships.

Monogamous voles, such as prairie voles, have significantly greater density and distribution of vasopressin receptors in their brain when compared to polygamous voles. These differences are located in the ventral forebrain and the dopamine-mediated reward pathway.

Peptide arginine vasopressin (AVP), dopamine, and act in this region to coordinate rewarding activities such as mating, and regulate selective affiliation. These species-specific differences have shown to correlate with social behaviors, and in monogamous prairie voles are important for facilitation of pair bonding. When compared to montane voles, which are polygamous, monogamous prairie voles appear to have more of these AVP and oxytocin neurotransmitter receptors. It is important that these receptors are in the reward centers of the brain because that could lead to a conditioned parter in the prairie vole compared to the montane vole which would explain why the prairie vole forms pair bonds and the montane vole does not.

According to evolutionary psychologists David P. Barash and Judith Lipton, from their 2001 book The Myth of Monogamy, there are several varieties of pair bonds:

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