Since homosexual couples cannot naturally reproduce, the question is, "What's biology got to do with it?"<quoted text>
I seem to remember Tippy and his brothers and sisters in arms singing loudly "What's love got to do with it?" when opposing gay marriage.
Now "loving couples" are trotted out as the gilded prerequisite for raising well adjusted children.
And Darwin says, "Everything."
Biology 101 --
Children are the product of a father [male] and a mother [female].
Every single time.
And the most ideal child-rearing occurs when that child is reared in a home with both parents present.