Prominent churchmen have worried that legalizing same sex marriage will lead to accepting polygamy in the future. To my mind they are underestimating the unique and innate drive for pair bonding that contributes to equality and unity in a marital relationship. Such mutuality is impossible for three or more. A dyad is unique because it is one relationship formed by two persons; it gains a intensity from its face to face, I-Thou quality. This power may be a legacy of mother-infant nursing in which mother and child commune in a loving gaze and pleasure filled dialogue. In this dialogue of giving and receiving, human selves are created—whatever the gender.
Cultures which practice polygamy give up the special mutuality of an equal dyad. Also, they pay a price in depriving poor young men of mates and endangering the equal rights of women. This privileging of powerful males provokes vigorous opposition to polygamy by both secular and gospel feminists. Apparently Christians won converts in the ancient world by their democratic ideal that each person could have equal access to the goods of pair bonded marriage.
Today the faithful should not be surprised that persons of different sexual orientation desire the goods of committed marriage and family creation. Promiscuity, temporary hook ups and friends with benefits do not provide psychological or moral sustenance in the long run—especially in old age. Permanent committed family relationships give persons the opportunity to not only receive but also give constant love, care and support. Altruism makes persons happy as the newly discovered “helper principle” shows.
Kinship and social connections are enlarged with marriage ties as well. “Your people shall be my people” as Ruth vowed to her mother-in-law. This human creation of kin beyond genetics is now thought to be one great evolutionary advantage of human groups. Humans are uniquely and wonderfully symbolic, meaning making, romantic creatures who create culture and institutions to embody love, sex, and cooperation. Marriage between two loving committed adult persons is here to stay, never fear.