Sex: the last real binary?

The rights of transgender and intersex people have become a contentious issue in our current political climate. Whether it be the rights of intersex athletes such as Caster Semenya (who identifies as a woman) to compete in elite sport, or the rights of transgender women to use women's only spaces, there is an increasingly fierce debate as to the legitimacy of people's gender and sexual identities and what parameters should be used to define them. A common argument accepted by most in our society is that while gender may be a spectrum, sex is an inalienable binary.