In spite of what some people think, not all cultures stick to two as the total number of genders.
Different Native American tribes have, for instance, throughout history allowed for what some call two-spirited, people who cross the boundaries between male and female in different ways.
As Micah points out over at CDL:
"People were valued for how they contributed to the tribe, rather than for their masculinity or femininity. Parents didn’t assign gender roles to children — even children’s clothing was gender neutral."
