The frequency of autism in modern humans follows certain patterns. Why is it that autism is more common in boys than girls? Why is autism more common in some populations than others? There seems to be a relationship between autism and exposure to testosterone in uterto. Although no proper scientific research exists devoted exclusvley to this subject, people have begun to speculate that there is a relationship between autism and neanderthal DNA. We know that all non-African humans have neanderthal DNA, but how does this DNA effect us?
It is now thought that the 2-4% of neanderthal DNA found in the average Eurasian today is different in each individual so that as much as 20% of the neanderthal genome exists in modern human populations. It doesn't manifest itself in the same way in all people, but rather is more pronounced in some than in others. Certain hormonal conditions during gestation may in fact cause latent neanderthal genetic tendencies to develop in children. Such tendencies were an evolutionary benefit to neanderthals existing on the edge of arctic regions during the ice age but are diagnosed as medical conditions today. There is evidence to suggest that lactose intolerance, crohn's disease, gluten intolerance, IBS, aspergers and autism may in fact be related to neanderthal traits passed on in mitochondrial DNA (that's the Mother's side) and then manifested physically as a result of high exposure to testosterone during foetal development.
In the future, research will show whether all this is nonsense or not, but the following video includes clips of scientific discussions on neanderthal DNA and how it effects modern humans, autism and its efffects and potential causes, and the nature of mitochondrial DNA. The juxtoposition of the different clips is intended to show that there is a relationship between said conditions and neanderthal DNA. Judge for yourself if you happen to have 2 hours and 18 minutes spare.
There is more information in this PDF