Ahhh.... that explains alot.

"According to Aristophanes in Plato's Symposium, in the ancient world of myth there were 3 types of people... In ancient times people weren't just male or female, but one of 3 types : male/male, male/female, or female/female. In other words, each person was made out of the components of 2 people. Everyone was happy with this arrangement and never really gave it much thought. But then God took a knife and cut everybody in half, right down the middle. So after that the world was divided just into male and female, the upshot being that people spend their time running around trying to locate their missing other half."

- Kafka on the Shore (Haruki Murakami)