There are many scientific explanations for why women are the way they are. I think there will always be less women in professional roles because women are expected to care for the children whether that is their main goal in life or not, it takes a lot out of a person to care for a little person 24/7, unless you put them in daycare.
I will offer personal experience. I don't know how all women are, but I know that I'm more than just a babysitter, even while watching my son. Like (In)Sanity was saying above, men are better at 3D spacial relationships and visualization, well I am better at that than most women I'm sure. I am the one who does all the handywork around the house, I troubleshoot the computer, I wire the entertainment system, research things before we buy them, I do many of the 'manly' tasks as well as being a mom. But I have noticed that other moms, and other women do not do these things, instead they go shopping, get their hair done, nails done, etc... I wouldn't mind doing that, but my first love is solving problems in my own home. I have heard that women are born business conisseiurs because they can multitask. I saw on a documentary I think on one of the Discovery Channels that like 5 women and 5 men were all given 10 tasks to do, some in order and some at random as they came up. Things like answer the phone, make popcorn, take care of the baby, etc... None of the men completed all tasks, but every woman completed every single one, so that make sense. But the women who are not hands on and ready to get their hands dirty to get something done aren't probably going to make very good mom's anyway.

But we definitely know that it is a woman's choice whether she chooses a career or a family or both. There are so many ranges of what a woman can do, however I think the biological pull to be a mom full time will make mothers and women in the workplace scarcer than men for the longterm.