So, I'm not really sure I buy this argument that there are more men than women in science because there are more men in the tails of the IQ curve. After all, being smart doesn't mean you're going to go into science, or that you'll be successful. An awful lot of other skills and aptitudes go into determining whether someone will be successful at any given career, including interpersonal skills, drive and ambition, dedication, and self-denial (just to name a few).
My suspicion is that the structure of a scientific career weeds out a lot of women who would otherwise make great scientists. There aren't enough spots at the table for all of us--women and men--and I suspect a lot of us women are simply more likely to take ourselves out of the running (many because of work/life balance issues) than men are.
I wonder what those female science-trained but no longer scientists end up doing once they leave. Do they come back? Or is a leave of absence pretty much an exit?