Celebrate your diversity, Heterosexuals!
Heterosexual marriage is the most diverse binary sexual relationship that Nature can provide. Two people of the opposite sex, equipped with wildly divergent anatomy, sexual responses, hormones, brain function and role expectations are expected to learn to cooperate with, understand, and learn to love one another.
Although lesbians and gays like to think of themselves as the bastions of sexual diversity, in fact the opposite is true. After all, what is diverse about two men in a relationship or two women in a relationship? How difficult is the sexual adjustment when both parties have the same attractions and sexual response patterns? How difficult is the living adjustment when you both leave the toilet seat up? Homosexual pairings are really just redundancy enshrined.
Think about it: heterosexuals need to learn to have an affinity for someone whose sexual preference is just the opposite of their own. A woman has to learn to respond sexually to a person who has a completely different set of attractions than she does. She is attracted to men, but is in a relationship with a person who has the opposite attraction -- for women. What a feat of tolerance and celebration of diversity!
Beyond mere co-existence with a being of such opposite orientation, the relationship is challenged with the ultimate example of synergy in diversity: procreation. The father has to use all the human powers of empathy to understand the feelings and needs of his pregnant wife. Lacking any commonality with the physical stresses of pregnancy, he must extend himself to the nth degree to understand the new mother's pains and discomforts.
He can't even nod his head knowingly and say, "I know just how you feel." If he even tried this, he would probably be banished to the sofa for the rest of the nine months. With such a daunting undertaking, the two opposite gender parents need to cooperate at the deepest levels to create a stable home life for the new baby. What could be a greater example of overcoming cultural, sexual or gender encapsulization than this situation? Strictly speaking, the most diverse relationship in human experience would be an interracial, age variant, religiously variant heterosexual marriage. Amazingly, some of these actually work. That miracle speaks well of the resilience of the human spirit!