What is it that makes a person a boy or a girl? From our cradles to our graves, a pair of letters, either XX or XY, will define much of our lives. "It's a girl!" or "It's a boy!" will be the first label applied to us, the first thing said about who we are as an individual. For every person in every society, gender has a fundamental affect on what we choose, how we live, and how we think about the world and how the world sees us. Sex is one of the most powerfully defining concepts that we have.

Of course, we assume that we know what this gender thing is: boys are boys, girls are girls. Sex is fixed, biologically determined, simple. But what if it isn't?

As Jane McCredie moves from laboratories to café tables, trying to find out exactly what sex is, the picture becomes much more complicated. Evolutionary psychologists, trans-gendered people, children playing with trucks and dolls, hormone specialists – they all have different stories to tell about what makes us girls and boys. These stories force us to stop and ask, 'is it really so straightforward?' Are we all really just stamped out in blue and pink? Leading us on a remarkable exploration of the ground where biology and culture meet, intertwine and ultimately blur, this book examines the new science which is helping us answer these important questions. Showing that we are far from "opposite" sexes, Making Girls and Boys will challenge everything you thought you knew about men and women.