I spent the day reading your paper and watching your video. Thank you for all the work you did! The evidence for the genetic basis of ASD is overwhelming. It seems like the results of the Neanderthal genome project support the Neanderthal theory as well. I also share your theory that ASD genes are preserved for eusocial benefit, although I don't know how you could ever prove that definitively. Why do you think the prevalence of ASD diagnosis is rising?
Thanks!
I initially thought that the rising prevalence was purely due to recent changes in selection pressure. An as-yet-unknown biological mechanism triggered by environmental stimuli might still be able to explain the sharp, non-Darwinian spike in recent cases, but the rate seems alarmingly high for something that's supposed to be adaptive.
It looks like DNA hypomethylation may actually induce copy number variation:
In particular, these so-called methylation deserts are spotted with copy number variations (CNVs), deletions or duplications of a length of DNA. Because some of the most well-documented genomic links to autism are CNVs, the new findings might help clarify the disorder’s genetic origins.Scientists had already known that parts of the genome with low-copy repeats — short, repeated segments of genomic DNA — are particularly susceptible to CNVs. The new research shows that lack of methylation may be just as influential, and is the first to make the connection between methylation and structural mutations of the genome.
If this is the case, perhaps we're seeing an accumulation of transgenerational epigenetic effects caused by biological mechanisms that had originally evolved to maintain a minority of ancestral phenotypes in a given human population, but were recently pushed into overdrive. Environmental contamination may alter these mechanisms in a manner that isn't easily tested within a single generation:
Gestational Exposure to Bisphenol A Produces Transgenerational Changes in Behaviors and Gene Expression
Here we show that BPA produces transgenerational alterations in genes and behavior. Female mice received phytoestrogen-free chow with or without BPA before mating and throughout gestation. Plasma levels of BPA in supplemented dams were in a range similar to those measured in humans. Juveniles in the first generation exposed to BPA in utero displayed fewer social interactions as compared with control mice, whereas in later generations (F2 and F4), the effect of BPA was to increase these social interactions. Brains from embryos (embryonic d 18.5) exposed to BPA had lower gene transcript levels for several estrogen receptors, oxytocin, and vasopressin as compared with controls; decreased vasopressin mRNA persisted into the F4 generation, at which time oxytocin was also reduced but only in males. Thus, exposure to a low dose of BPA, only during gestation, has immediate and long-lasting, transgenerational effects on mRNA in brain and social behaviors. Heritable effects of an endocrine-disrupting chemical have implications for complex neurological diseases and highlight the importance of considering gene-environment interactions in the etiology of complex disease.
This appears very troubling, but problems aren't solved at the level of awareness that created them (not to be confused with the fallacious yet tragically pervasive assumption that "Problems aren't solved until they're completely dissected, codified, stuffed and mounted below one's ego"). The academic community seems entirely unable to openly discuss the Neanderthal-autism link, not because of a scientific hurdle, but because of an ideological one. The internet should eventually decentralize higher education, eliminating this problem. Until then, limited progress towards answering your question might be achieved through increased awareness in the autism community. I haven't met a single autistic (or parent) who failed to respond positively to my hypothesis (a few people who have had no personal experience with the condition have managed to work themselves into a right tizzy, but that's to be expected). Baron-Cohen has admitted via email that backlash from the MMR study has discouraged open dialogue between researchers and the public, so it's quite possible that the Max Planck Institute is already silently working on this.
If someone could crowdfund a small study that showed a definitive link, perhaps the subsequent public attention would convince academic institutions to take this seriously.