Not enough women in science?

Are women underrepresented in science?  My philosophy professor was complaining that since half of all B.Sc. grads are females, it doesn't make any sense that there are so few female science professors.  Personally, I don't see what the problem is.  It's not like scientific progress is being impeded by gender inequality.

Spoilers: women have smaller brains and lower IQs than men on average (5 points less in adulthood). That means there are MUCH less women in the typical science prof (135+) range. A science BSc on the other hand only takes an IQ of about 105 and a decent work ethic.

There are 1000 politically correct answers to the OP's question but none of them are as convincing as the paragraph I have just presented.