I also think that the reason women so dominate or make up significant portions of some industries and professions is cultural and historical.
I have to disagree - I think much of it is biologically based. Women bear and raise children and I think are more drawn to fields that involve people (caring for them, nurturing, education, etc) then men. I think this is demonstrable even over the past few decades when concerted efforts have been made, starting from childhood onwards to change this preference. These efforts haven't succeeded from what I can see. I would say that the cultural and historical trends evolved from and reinforced the innate biological ones.