If this is a genuine question, and not a halfhearted attempt at trolling, you need to be more specific about what you’re asking:

Are you looking for biological / evolutionary theories about why maaaaany animals show same sex sexual activity?

Are you looking for an anthropology/historical analysis of how human sexuality has been expressed in different ways and had very different norms and taboos than our current blend?

Or are you asking individuals to talk about their own experience and what lead them to identify as whatever?