It sounds like a compelling reason, and it gets a lot of play. Except, you know what? It’s a lie.
My first degree is in mathematics. So I looked up the studies. I did the math. And it just didn't add up. The research into biologically-linked ability is fascinating, but it simply isn't significant enough to explain the huge gender gap we see in the real world. I used to do this presentation on the back of a napkin for people who tried to spout this misconception to my face, and I finally put it online:
How does biology explain the low numbers of women in computer science? Hint: it doesn't.
Love it? Hate it? Learn something? Catch the Mathnet reference? Let me know.
These slides have also been posted at my personal blog, geekfeminism.org, and GHCBloggers. They've been impressively popular on facebook and twitter too, and even got used recently in Kirrily Robert's keynote at ApacheCon. Please feel free to keep passing them on, and I'm sorry I didn't think to post them here sooner!