...Besides children, women who carry the burden of pregnancy are obviously at greater risk than men in the childbearing process. Historically, gendered marriage has tied men to their children and to the mothers who sacrifice to create them. This arrangement not only overcomes but also compliments the biological differences of men and women.
Finally, gendered marriage addresses the rights of fathers. Fatherhood is the most fragile biological relationship in the father-mother-child triangle. The bond between mother and child is obvious. The father less so. Marriage closes this gap by legally binding a father to a mother and child, giving him both rights and responsibilities in a relationship that, by the way, dramatically affects the successful socialization of children.
This observation is from is a Mormon magazine, but this argument is based in biology, not theology. The problem is that for the past half century our culture and law have made a priority of minimizing the differences between the sexes. If one accepts contemporary feminism's premise that men and women are essentially interchangeable, it is very difficult to formulate a coherent reason why, for the purposes of marriage, one of each should be treated any differently from two of one or the other..