Tee hee. Sex.
Sorry. Let's talk about Laqueur. He's interested in the way we understand the difference between men and women. Contemporary writers have often distinguished between sex (the biological difference between men and women) and gender (the culturally constructed roles we assign to men and women). Laqueur's basic argument is that it's more complicated than that, and he traces the history of the different ways people have understood sex in order to argue that the way we see biology is inextricable from our culturally constructed ideas about what it means to be men and women. He writes about three different ways of understanding the male/female difference: the ancient one-sex model, associated with Galen; the ancient two-sex model, associated with Aristotle, and the modern two-sex model.
Galen's idea (Galen was one of the earliest doctors) was that there's basically only one sex, and that women aren't fundamentally different to men but are just weaker versions of men. Part of the reasoning behind this was the idea that female genitalia were just the inverse of male genitalia, which came from the physical similarities between them: so the ovaries were roughly equivalent to the testes and the vagina to the penis (if you draw it right, it does look a bit like and inside-out penis). His idea was that men were hotter than women (temperature-wise, that is), and the greater heat in their bodies pushed their genitals out, and also for the fact that they were, generally, better. It also meant that the boundary between male and female was fluid, and men were always threatened with the danger of becoming female (so had to make sure they acted sufficiently bloke-ish to avoid this), and that if girls behaved in inappropriately male ways, they might become men (Laqueur relates some funny folk tales about girls acting like boys and then - whoops! - a penis suddenly appearing).
Aristotle, on the other hand, advocated a model which saw men and women as essentially different. He associated men with soul and reason, and women with matter and physicality. In his biology, it was the sperm which gave life, and women were just the receptacle. His account is less funny, but no less misogynistic. Are you starting to see now how we read culture into biology?
Laqueur's main point is that, around the 18th century, a new model for understanding the male/female difference emerged. It saw men and women, for the first time, as "opposite sexes". This was very much related to new discoveries in biology, though these too were very much culturally interpreted. For example, around this time the first drawings of the female skeleton emerged. No one had bothered to draw a female skeleton before, because everyone had assumed that male and female skeletons were pretty much the same, but now people became determined to find the differences because they became convinced (before the emergence of any evidence that would force this view) that men and women we completely different in every part of themselves. For a while, it was thought that women's skulls were smaller, suggesting (naturally) that women were stupider. Then it emerged that, proportional to their bodies, women actually had larger skulls. Aha! said the scientists. We all know who else has a big skull proportional to their body - children! Women, then, must be childlike - i.e. stupider than us. Nice. It was this sort of reasoning which led to the study of racial differences in biology, an interest which waned in popularity since - I wonder why?
The key point is this, though: science is never culturally neutral. It always interprets, and can never be fully disentangled from ideology and prejudice. What's the difference between men and women? Now there's a question. Maybe we'll come back to it later.