A comment on my last post reminded me of something, the frequency of autism and Asperger's syndrome being diagnosed has increased greatly over the past century. This might lead some people to believe that these disorders are fairly recent additions to the human genome and are becoming more commonplace. Well, they're not.
Asperger's and autism, or at least the traits associated with those mental states, have been present in the hominid family for millions of years, if anything neurotypicalness is a recent abnormality and autism is the original mental state of humanity. In my opinion the only reason why autism-spectrum disorders are being diagnosed more and more frequently is because psychologists are widening the criteria and getting better at identifying them. Also our population has increased by several orders of magnitude in the last 10 millenia so there are more people in general. In short there have been auties and Aspies since before "neurotypical" humans evolved and it's only recently that Psychology has noticed that some people think differently than others. In addition there are people with "shadow syndromes" that have carried the genes for autism-spectrum disorders during times when people with the full disorders might have been easily noticed and persecuted (like the Middle Ages).