I'm just speculating, but network effects are extremely important in science and I see it as very possible that women might have a harder time networking (presenting their papers, talking to peers, given benefit of the doubt by peers, etc.) in a field that is dominated by men. My SO did her bachelors on AA in big corps and found a lot of studies that supported the hypothesis that males bosses statistically tend to promote and acknowledge the work of other males more than of their peers. (Though I have to concede that it was just a bachelors degree and could also have been badly/unbalanced researched and that I am too lazy to find citations, as I have no clue of where she got them.)
>American universities train roughly twice as many Ph.D.s as there are jobs for them. When something, or someone, is a glut on the market, the price drops. In the case of Ph.D. scientists, the reduction in price takes the form of many years spent in ``holding pattern'' postdoctoral jobs. Permanent jobs don't pay much less than they used to, but instead of obtaining a real job two years after the Ph.D. (as was typical 25 years ago) most young scientists spend five, ten, or more years as postdocs. They have no prospect of permanent employment and often must obtain a new postdoctoral position and move every two years. For many more details consult the Young Scientists' Network or read the account in the May, 2001 issue of the Washington Monthly.
Measurements of metric are objective only from the people who establish them, who are biased. Even if the professor is right, challenging meritocracies is always valuable and necessary.
This doesn't mean you should throw away all systems for selecting people to do a job; it means examining we must examine the consequences of using those systems and examining whether they are a net positive not only for the work you're doing but for society as a whole.