Study says gene encourages monogamy. A single gene, which controls the expression of a receptor for the neuropeptide vasopressin in the ventral pallidum region of the prairie vole, apparently makes all the difference between the monogamous mating behavior of this species and the promiscuousness of the closely related meadow vole species. Inserting the vasopressin receptor gene in the proper brain area in meadow voles makes them strongly prefer their current mate just as the prairie voles do, and blocking the effects of vasopressin at the newly expressed receptors makes them revert to their noncommittal behavior. The implicated region is involved in mediating the brain’s reward system, and it is hypothesized that prairie voles feel a sort of reinforcing pleasure with their mates that is absent in the meadow vole. (Boston Globe)