4/5
I would rather try and illustrate with something like original sin, but you raised gay marriage. Perhaps the prime continuity inspired by the Spirit is natural law, the attempt to find moral guidance in nature. Our ancestors in the faith noted quite correctly that sex in nature is for procreation, and perhaps because “sexual jealousy” is natural enough, and since human children need parenting for a very long time, they decided that monogamous pair-bonding is the proper context for sex and children. Without reliable forms of contraception, prohibition of sex outside of marriage was a pretty good rule with a view to society living in conformity with nature.

Critically important, I think, is that in the world that devised those rules, human nature was understood as “body + soul” (biology + spirituality). Today, because of the discovery of psychology, we thing more in terms of “body+ psyche + soul” (biology + psychology + spirituality).