Men do better than women at the Math SAT[1]. The male/female ratio is especially high in the higher Math percentiles, where you would expect your best engineers to come from. The polite way to explain this is some kind of "expectations effect", which is possible, but females do dominate at all other aspects of education. We cannot rule out simple innate ability, combined with higher male interest in abstract things.
[1] http://www.aei-ideas.org/2012/09/2012-sat-test-results-a-hug...