More evidence has recently appeared stating that many modern Homo sapiens carry a small percentage of Neanderthal-derived genes, possibly as the result of interbreeding that occurred around the time of man's great leap forward. Although these results are still subject to further investigation, the data does provide some confirmation of earlier findings, suggesting that a consistent picture is beginning to emerge.
Near the end of my essay Reflections on the Work of Richard Klein, I engage in some speculation that these Neanderthal-derived genes could be the material source of autism everyone is looking for. The idea is that beyond a certain threshold, a large enough presence of Neanderthal-derived genes would make it difficult for an individual to recognize and attach to the other members of Homo sapiens around him, and this lack of species recognition and species-focused perception would in turn engender the broad array of autistic behaviors so frequently observed.
If this speculation is going to have any legs, what we might expect to see next—probably within the next couple years or so—is the emergence of studies highlighting a significant correlation between a larger presence of Neanderthal-derived genes and the occurrence of such conditions as schizophrenia, bipolar, and autism. If such studies do begin to appear and if they turn out to be accurate, this would have the effect of raising my idea from one of mere speculation to intriguing possibility.
Nonetheless, I'm not exactly married to the idea—the material cause of autism could easily end up being found elsewhere. What I do want to point out, however, is that right or wrong this idea does demonstrate that there are legitimate means of examining genetic difference besides just assuming genetic defect. The current fervor within the autism research community to presuppose that every barely significant genetic difference must result inevitably in synaptic damage or connectivity dysfunction (or whatever happens to be the neurological affliction flavor of the day)—well, let's just say that this approach has betrayed both a bankruptcy in results and a bankruptcy in vision. Autism researchers have been demonstrating that they understand almost nothing about the mechanics of genetics, and have been demonstrating very little else.
One more thing. Even if it turns out that the presence of Neanderthal-derived genes are correlated with the presence of autism, this does not mean that Neanderthals possessed autistic-like characteristics and that these characteristics are somehow being expressed through the genes. This is another poor way of looking at the mechanics of genetics, and even worse, it is a poor way of looking at anthropological history. We have only limited archaeological information regarding Neanderthals, but what little information we do have suggests a very primitive, quite animal-like existence, not dissimilar from that of early Homo sapiens. It is an overly romantic and all-too-common fallacy to ascribe modern human behaviors to our ancient ancestors, not recognizing that almost the entire panoply of modern human behavior was developed only quite recently, and this would hold true for most autistic behaviors as well. Ancient humans—that is, humans prior to man's great leap forward—are not described best as either autistic or non-autistic. They are described best as animal-like. And to recognize the massive scale of the intervening transformation is to recognize why all these questions and speculations are so terribly important.