Transsexuals and transgendered people can often tell us a great deal about our society because they've experienced what most of us never will: being perceived as a man or a woman in the same lifetime.

A worthy read on this topic is Kate Bornstein's Gender Outlaw, which chronicles some of her experiences as a transsexual woman. One memorable passage describes the first time Kate walked into a store after being able to successfully pass as a woman. She was shocked to find that nobody was treating her with any respect. A so-called "normal" woman who's been a woman her entire life would never know the difference.

Ben A. Barres, a neurobiologist who happens to be a transsexual man, wrote a commentary for Nature about sex differences in scientific ability. Barres started out his career as a female scientist and then transitioned to being male. Consequently, he personally experienced how differently people treat male and female scientists. Largely spurred by the Larry Summers controversy, Barres' article makes a convincing case against purely biological explanations for gender differences. If you're interested, the full article can be viewed here.

In Gender Outlaw Kate Bornstein writes, "I know I'm not a man...and I've come to the conclusion that I'm probably not a woman, either...The trouble is, we're living in a world that insists we be one or the other."

But are we really? Most people reading this blog probably think so, but there are cultures on our planet that recognize more than just two genders...more on what that looks like later.