Another thing to consider is that humans have a brain powerful enough to override human instincts. For example, we are born with an instinct to reproduce, but we can choose not to.

This also applies to our sexuality, personality, gender, behaviors, preferences, and more. We don't have to conform to instincts, norms, or stereotypes.

Since that is the case, unless you're strictly talking about anatomy, two sexes aren't an accurate way to describe human sexuality.