In our current culture, sexuality is almost entirely defined by your preference in gender, but my understanding is that this was not always the case. People from hundreds or thousands of years ago would not have understood the concept of homo or heterosexuality, and used entirely different criteria.

So my question is, when did these modern ideals arise, and how? Did it stem from an 'othering' of the gay community that simply never went away, or is it more complicated than that?