The pieces of the puzzle seem to fit together. If I were to read the minds of the researchers in these domains, I suspect they're beginning to think of autism and schizophrenia as examples of an entirely new class of illness - "evolutionary disorders". These are a class of disorders that arise in an organ, in this case the brain, that is undergoing rapid evolutionary change with a high mutation rate and a lot of suboptimal experiments.
I used to think that human evolution more or less ended with the invention of fire, at least that's what I recall from my high school essays . Now we know that the human brain and human gut (they're very closely related systems) have undergone major adaptive changes within the past 15,000 years. It's increasingly plausible, but I don't think it's been proven, that these are systems predisposed to high mutation rates .
Systems predisposed to high mutation rates are going to produce a lot of "suboptimal" results, and a few significant improvements. This is what may account for the perplexing prevalence of two syndromes, autism and schizophrenia, that share similar traits:
- no obvious adaptive advantages
- ill-defined and probably multiple underlying pathophysiologies
- complex genetic variability -- many different identified mutations and a suspicion that the disorders may arise from interacting protein networks.
 I've been fascinated by human evolution forever. Even as a child I didn't care for the traditional eugenics that is increasingly commonplace today, so I then advocated the encouragement of inter-ethnic marriage to dilute "bad" genes -- until we could directly engineer germ cell lines. Hey, it was a long time ago ...
 I think the theory here is that mutation rates can be selected for, so when "rapid change" is advantageous there is selection for "genomic creativity" over "genomic conservation". I think that's the mechanism that's supposed to underlie "punctuated equilibrium", but I'm not a biologist. I just write to learn ...
Update 5/6/2010: Yes, they're evolutionary disorders. In 2010 the term "evolutionary disorder" has a lot of hits, but I may have been one of the first users of it in this context.