“As to the “deeply physical, emotional, and spiritual act” you say sex is, I would just point out that there are a LOT of people disagree with you. I personally don’t see anything spiritual about it at all, and I think the only emotional thing about it is what you choose to invest in it. As for it being “deeply physical,” so is a back rub or playing football or wrestling.“
During the middle ages, women were seen as especially sexual and as therefore especially sinful. This changed in the early nineteenth century when women came to be seen as sexually passive, and therefore especially virtuous and moral. Women used their ascribed virtue to champion a variety of reform issues, and the church became overwhelmingly female as men gravitated toward work outside the home and a political life in the public sphere and women came seen as the keepers of the home, the nurturers of children, and the keeper of the family alter. Care for children’s spiritual state transferred from the father to the mother during this period as well. All of this, though, was predicated on women’s especial purity, which rested upon their sexual passivity. Close your eyes and think of England, anyone?
The first few decades of the twentieth century also saw further challenges to the gender hierarchy with the coming of the “new woman,” who worked outside of the home, cast aside her corsets and donned short skirts, dated, danced, and drank. I think it likely that the opening up of new options for women, which began to pick up speed in the late nineteenth century with the rise of job options for single women in new technologies such as secretarial work or telephone operating, was necessary for the development of the companionate marriage, which uncoupled marriage from economic necessity and instead coupled it to ideas of love between two (relatively) equal partners.
But of course, evangelical and fundamentalist Christians do not see their ideas about sex as a social construction. I earlier pointed to bonobos, dolphins, and ducks by way of comparison, but Christians believe that God has set man apart from the animals, giving him a soul and making him special. Given this, evangelicals and fundamentalists hold that sex is naturally and always much, much more than just a physical act – it is, and always will be, a highly intimate, emotional, and spiritual act that should only take place within the bonds of matrimony. And, they contend, this isn’t a construct – it’s simply the natural way of things as set up by God.