This theory is proposed by Leif Ekblad, a self-described Aspie, author of the well known Aspie Quiz and the Rdos operating system, and also the parent of children somewhere on the autism spectrum.
The theory basically says that behaviors classified as spectrum disorders in the field of psychiatry could be explained by genetic introgression from another species, namely the Homo Neanderthalis. Therefore, the author concludes, psychiatric disorders are not dysfunctions but rather differences, and psychiatric patients are, in general, functional.
The author points out that even though a Neanderthal ancestry for Homo Sapiens has been ruled out through mitochondrial DNA (mother line), hybridization is still possible. Neanderthals and Homo Sapiens coexisted in Europe for a long time.
Evidence and possible predictions
- The DRD4-7R allele has been linked to ADHD and to a behavior known as novelty seeking (presumably more common in migratory humans) and has been found to be considerably more prevalent in Europe than in other parts of the world.
- The diet of Homo Neanderthalis consisted almost exclusively of meat [ref]. If autistics have Neanderthal physiology, this would mean a high-carbohydrate diet is not the proper diet for an autistic individual as it might result in GI tract problems. The digestive system of Homo Neanderthalis was probably not adapted for diets high in gluten and casein. In the modern world, a more appropriate diet would be a Ketogenic or Atkins diet. A Neanderthal child in the modern world would probably suffer from a deficit of L-carnosine.
- The Neanderthal skull had a volume about 13% larger than that of Homo Sapiens. This likely resulted in certain cognitive advantages but also liabilities. Bigger head circumference in a subset of autistic children has been documented. (It is not clear if this difference is maintained as they grow, however). This also explains labor complications. Combined with a normal-size skull, a bigger brain could also result in a number of medical complications.
- Some researchers believe Neanderthal's language was simple, with limited vocabulary and grammar.
- Neanderthals were expert tool-markers. Their tools were extremely prevalent and the tool-making appears to have required some level of perseveration.
- Some believe Neanderthals were actually smarter than Homo Sapiens (due to their bigger brain capacity) but failed to survive because of their relative inability to communicate well. This is consistent with Dawson-Mottron (2005).
- Intonation and voice pitch were likely different in Neanderthals. This is a common problem faced by Asperger autistics.
- Although nothing is known about Neanderthal eye contact, lack of it is common in other primate species.
- Neanderthals had "rodeo-type" injuries, which might suggest they had different sensitivity to pain.
Problems with the theory
- Based on the Occam's Razor principle, I would conclude this theory is not necessary to explain autistic behavior. It is not surprising that great diversity in socio-linguistic skills exists in human beings, and that the bottom 1% (or some other arbitrary boundary) is established as the disorder boundary in the behavioral spectrum. Some behavioral spectrums have different disorder boundaries. For example, in the hyperactivity spectrum, the boundary is situated at the top 5% to 10% of the population. This probably results from the desires of school officials to control hyperactive children by means of medication.
- If this theory is correct, we would expect autism and ADHD to be disorders almost exclusive of European populations. They would be unheard of in Asia or Africa. It is known that the prevalence of autism does not have any significant ethnic dependency. (The author cites the prevalence of online sites from different parts of the world, but this observation clearly suffers from a serious methodological flaw).
- No evidence exists suggesting that any hybridization with Homo Neanderthalis occurred.
- Autistics have been described as having low sex drive and an inability to resolve romantic relationships. Assuming these are innate characteristics which do not result from psychological factors or cultural incompatibility, then the Neanderthal Theory does not seem to hold water. It is unlikely Neanderthal would have survived as long as they did if members of the species had these characteristics in a significant proportion.
- We might expect autistics to have a characteristic look. Instead we find that autistics look unremarkable, and are often even described as attractive. (It is possible Neanderthals were attractive, but we can't draw any conclusions either way. Some adult autistics report a brow ridge, but this is purely anecdotal).
- It is unclear how this theory explains some of the more severe symptoms of psychiatric disorders, such as self-injury.
- It is unclear if autistics socialize better with other autistics than with non-autistics.
- The author's contention that small skull combined with a large brain might result in low-functioning autism is not necessarily consistent with known findings and cannot explain Dawson-Mottron (2005).