Baron-Cohen reports on questionnaire research that has found a higher percentage of men than women to fit an approach-to-the-world type he calls “systematizers” (54% vs. 17%). Men are correspondingly less often “empathisizers” (17% vs. 44%). Autism, he proposes, is symptomatic of an extreme systematizer-type brain with “an unusually low drive to empathize”.
You start with the child with autism; he or she is the end result of this experiment of nature. And you work backwards to see if there were there clues in the previous generation — or previous two generations. This new theory is called "the assortative mating theory", The clue that both sides of the family are contributing similar genes is that in our study of occupations, grandfathers on the maternal and the paternal sides were both more likely to be working in the field of engineering. So the strong systemizing wasn't coming down just one side of the family. It's called assortative mating because it describes the idea that two individuals might end up in a union because of having similar characteristics. They're selecting each other on the basis of having similar characteristics.
He also blames an environment that puts too much emphasis on being politically correct:
My thesis with regard to sex differences is quite moderate, in that I do not discount environmental factors; I'm just saying, don't forget about biology. To me that sounds very moderate. But for some people in the field of gender studies, even that is too extreme. They want it to be all environment and no biology. You can understand that politically that was an important position in the 1960s, in an effort to try to change society. But is it a true description, scientifically, of what goes on? It's time to distinguish politics and science, and just look at the evidence.
Baron-Cohen and others debate about the assortative mating theory advanced by him.