Meh, I dunno.
Let's face it, kids -- the vast majority of the female population is NOT mechanically inclined. It's a simple fact of how the female brain is wired. Natural impulses, tendencies, yadda-yadda. Sexist? Yes. True? Unfortunately, yes...
If it was the only option, everyone would learn to drive a manual. Some would take longer than others. You can't say women specifically don't have the ability to learn. Some PEOPLE just choose not to learn how to drive a manual, not because they aren't mechanically inclined, but because they don't have to learn. Men are more inclined to have interest in a car beyond it's ability to get you where you want to go, that's why more men have manuals. it's personal preference. not genetic ability.