Saturday, March 18, 2006

Review: The Neanderthal Theory of Autism

Even though the Neanderthal Theory of Autism does not appear in the formal autism literature, it is intriguing and I believe it should be addressed and studied as any other autism theory. I will provide an overview of the theory, some evidence in favor, and finally I will list significant problems I've found this theory suffers from.

Overview

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).


22 comments:

  1. I don't know about this.

    It sounds really interesting. Imagine if we could trace autism back to the beginning of the world and of human civilisation.

    ReplyDelete
  2. Well, I think it's possible Neanderthals were fairly autistic, and that autistics are somewhat like Neanderthals. As to causation, I'm not sure.

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  3. Hi Joseph
    How this theory can fit in the increased number of glutamate receptors found in some children with autism, and as you say, Dr Mottron group work?
    How do we know the neurobiological reasons of the behaviors of Neanderthal, even if a correlation or similarity in some behavioral areas can be pointed out?
    Honestly, I do think that without this information nothing can be concluded but in general I agree with you that can not explain a lot of ASD.
    Thank you for this post. I knew nothing about this theory.

    María Luján

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  4. How this theory can fit in the increased number of glutamate receptors found in some children with autism, and as you say, Dr Mottron group work?

    Obviously the theory would say that Neanderthals had more of these. This is an unfalsifiable aspect of the theory (unless we were to clone Neanderthals) it would appear.

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  5. Well, a nice review. Some comments:

    Sex drive. We researched "asexuality" in Aspie-quiz. It turned out that asexuality clustered with social traits and not sexual deviations. Therefore, the fact that many Aspies claim to be asexual is not a problem, since it is not likely to be inherited.

    The prevalence of autism. The theory only predicts that Africa will have lower prevalence, and not Asia. Neanderthals lived in central Asia, and this is were Hss first came in contact with Neanderthals. The East Asian (mongoloid race) very likely have high levels of Neanderthal / autistic traits. This is also confirmed by various racial studies of IQ and other traits.

    It is pretty "well-known" in the autistic community that there is considerable asortative mating going on.

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  6. "It is unclear if autistics socialize better with other autistics than with non-autistics."

    I wouldn't say that it is very clear,but 80% of all the friends I've had throught my life were on the spectrum (so am I).

    Also do to the nerologoical nature of ASD itwould make sense that autistics could interact better with of autistics than with NTs

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  7. This reminds me of the origins of the word "mongoloid" when talking about people with downs syndrome.

    The person who named the syndrom, Down, saw people with downs syndrome as throwbacks to some previous stage of evolution - namely, non-europeans.

    He figured people with downs syndrome where basically of the mongoloid group of people - which neatly explained their lower IQ's in his view.

    These days it is politically incorrect to call people with Downs syndrom mongoloids.

    Personally I would rather be associated with the proud horse-warriors of the steppes than with some senile old racist.

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  8. The difference in this case is that the person proposing the theory I don't believe assumes Neanderthals were a "previous stage" of evolution (either inferior or superior). In fact, it is well known they weren't. They were just a different species of human.

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  9. A new version of the theory, incorporating two years of research with Aspie-quiz, is now available. Many of the claims that were previously unreferenced are now backed-up with correlations from thousands of autistics and non-autistics answering on Aspie-quiz.

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  10. Hello
    I've been diagnosed with Asperger's syndrome and to me, the theory makes loads of sense.
    Did you know a hybrid child has been found in Portugal? He died long after Neanderthals were supposed to have been extinct. For such traits to survive the degree of interbreeding would have been significant.
    I'm going to research this topic more!

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  11. This is a very intersting theory but i do not think it will hold up in the long run.

    Frist of all hybridization is rare in the wild. Even chimpazze and bonobos do not interbreed despite considirable dna simularity and despite the fact that they live close to each other.

    Secondly,it is inconclusive whether the fossil found in protugual is a hybrid, and while some scientists say that it is, others say that the morphology of the bones in within the realm of human variation.

    Lastly I'd like to point out the multiregional vs out of africa debate. While both sides of the debate have credible evidence, dna studies have given the "out of africa" side an edge.Human dna is remarkably uniform and studies on mitochondrial and y chormosonal dna have shown that populations around the world can trace ancestry back to africa. Also sub saharan Africans have the most amount of dna varaition than other group of people and this is consistant to what you would find if humans originated in africa.

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  12. The Portuguese remains of a four-year-old child are one *hybrid* case. A second fossil, older, has been found in Romania, and a less clear-cut fossil [much older] in Israel. Stay tuned.

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  13. While I would agree that it's a very speculative theory at this point, I did a little digging and what I found intrigued me.

    If you look at haplogroups, it seems plausible that significant segments of the Scandinavian and British populations have DNA which traces back to the Iberian penninsula. This coincides with their tending to have skulls which are longer (front to back) than usual for our species.

    Because there is also DNA evidence which points in the direction of our having done some inter-species breeding in the past, I'm keeping an open mind on the whole thing.

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  14. (No evidence exists suggesting that any hybridization with Homo Neanderthalis occurred.)

    Actually there is a fair amount of evidence that hybridization did occur. We have hybrids at 24,000 and at 28,000 ybp. I have posted the latest hybrid find on my blog.

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  15. What would be the levels of aspeger or autism within the Basque populations of the Iberian peninsula?

    That would be interesting to know.

    A large percentage of the Spaniards that arrived in the Americas were also Basque, along with converted muslims and jews who no longer had a home after the reconquest of 1492. I wonder what the levels of aspegers would be for the European, Mestizo and Mulatto populations in Latin America.

    ReplyDelete
  16. Well I did (leave my comment, that is!) and now it's gone! I'm gwynfryn and I wonder if there is anyone out there who notices how my posts keep disappearing? If truth means anything to you, then copy this now:

    gwynzkind@yahoo.co.uk

    call me there any time.

    ReplyDelete
  17. No messages are deleted here without my stating that a message has been deleted. I'd suggest you get a screenshot the next time you post a message.

    ReplyDelete
  18. Apologies Joseph, and I don't know if the deletions I referred to had anything to do with your blog.

    Another blog has at least made possible my links, so maybe it's possible here too?

    One treatise on the possible origin of autistic minds is my very own, originally posted here:

    http://www.awares.org/conferences/bb.asp?section=000100010002&conferenceCode=000200010009&forum=000100100073

    It refers to an "official" autism charity run site which anyone can join (if paying a fee, recently) by merely entering (a few of) their details.

    If any reader finds this of interest, please don't imagine that the following year's post is any of my doing?

    If you want what I actually wrote; Joseph knows my e-mail address.

    ReplyDelete
  19. I've been exploring a theory that runs parallel to this one. See http://www.neoteny.org/?cat=7. The similarity is that I'm hypothesizing that autism is a drift back in the direction of our ancestors, not Neanderthal, though.

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  20. your spot on i know i think in the same way so does my daughter we have the same build same shaped head same problems well we would have if i felt the need to fit in as she does and i think we can read people to well thats what scares them we both look right in to thier eyes i have also just realised i can't hear say or process certain vowels im not sure where the problem lies we have also other members of our family which are the same but they think its easyer to ignore it how wrong they are

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  21. I am an adult female diagnosed with ADD and a lay scientist with a knack for seeing the bigger picture.
    As an adult, I searched for answers for my obvious differences & came to the conclusion that despite my upbringing, I belonged to an earlier time of ancient peoples that were more connected to nature & seasons. This stimulated me to begin looking into my ideas & feelings in greater depth and from my own personal research by reading books by respected authors in the field, the web, my own subjective experiences & observations & opinions. I had already surmised that there might be some connection between myself & Homo neandertalis which I found hard to believe could disappear without trace & without any inclusion into the modern human genome.
    Just imagine my excitement when I first saw the Neanderthal Theory of Autism which included evidence of a connection with ADD traits published on Wikipedia!
    There are remarkable coincidences between certain characteristics of Autistic & ADD behaviour & appearance with the ones that Neanders are conjectured to have.
    The evidence of the tracings inside one Neander brain case seemed to suggest that the areas for short term memory & retrieval were relatively weaker than the area relating to long term storage, a difficulty reported by many neuro differents(NDs) or all those said to have medical conditions arising from differently wired neurological functioning & processing.
    As far as appearance goes and the fact that NDs do not necessarily look particularly "odd", this is hardly surprising given that we will be massively hybridised with Homo sapiens both ancient and modern and that Neanders themselves were certainly recognisably human to the modern onlooker.
    However, I‘ve observed that there are certain physical traits that everyone one I know that is ND share. We generally recognise each other straight away and can communicate and socialise with greater ease amongst ourselves.
    We are often highly attractive. Computer generated images of Neanders have produced some striking looking individuals with prominent features, large heads, soft pale skin, green or pale coloured eyes adapted to lower light levels, often beautiful red hair, a fine physical build and possibly more hirsute. Some of these and other conventional Neander features I have more commonly observed in today’s population of NDs.
    I believe the question of a lower sex drive amongst NDs is a little unfair & is typical of a more competitive, quantity over quality mentality. It is true that of those NDs I met, fewer seemed obsessed by sex and can appear quite shy in these matters.
    Yet, when it comes to relationships between NDs & NTs, it has to be recognised that it is very difficult to enjoy love, understanding & sex with a person possessing fundamentally different attitudes to ourselves with which it is not easy to communicate.
    Between ourselves, I have observed a little more success in the field, though' because of our individuality, it always represents a challenge. The temperament of the ND can also be quite different sexually from that of the NT.

    The point is, on every level, our minor genetic differences can interact quite massively with our lives. The modern world, being so fast & challenging & extremely hide bound in convention is problematic, much as it would be on the lives of more ancient peoples. Scientists are finding increasing evidence that Neanders were a sophisticated people with the power of speech & not primitive brutes. In my opinion, differently hard wired brains, not caused by accidental brain damage must be a result of genetic differences passed on by alternative types of humans. Far from having a mysterious genetic abnormality, we are as we are because we were genetically designed to be that way..

    ReplyDelete
  22. I am an adult female diagnosed with ADD and a lay scientist with a knack for seeing the bigger picture.
    As an adult, I searched for answers for my obvious differences & came to the conclusion that despite my upbringing, I belonged to an earlier time of ancient peoples that were more connected to nature & seasons. This stimulated me to begin looking into my ideas & feelings in greater depth and from my own personal research by reading books by respected authors in the field, the web, my own subjective experiences & observations & opinions. I had already surmised that there might be some connection between myself & Homo neandertalis which I found hard to believe could disappear without trace & without any inclusion into the modern human genome.
    Just imagine my excitement when I first saw the Neanderthal Theory of Autism which included evidence of a connection with ADD traits published on Wikipedia!
    There are remarkable coincidences between certain characteristics of Autistic & ADD behaviour & appearance with the ones that Neanders are conjectured to have.
    The evidence of the tracings inside one Neander brain case seemed to suggest that the areas for short term memory & retrieval were relatively weaker than the area relating to long term storage, a difficulty reported by many neuro differents(NDs) or all those said to have medical conditions arising from differently wired neurological functioning & processing.
    As far as appearance goes and the fact that NDs do not necessarily look particularly "odd", this is hardly surprising given that we will be massively hybridised with Homo sapiens both ancient and modern and that Neanders themselves were certainly recognisably human to the modern onlooker.
    However, I‘ve observed that there are certain physical traits that everyone one I know that is ND share. We generally recognise each other straight away and can communicate and socialise with greater ease amongst ourselves.
    We are often highly attractive. Computer generated images of Neanders have produced some striking looking individuals with prominent features, large heads, soft pale skin, green or pale coloured eyes adapted to lower light levels, often beautiful red hair, a fine physical build and possibly more hirsute. Some of these and other conventional Neander features I have more commonly observed in today’s population of NDs.
    I believe the question of a lower sex drive amongst NDs is a little unfair & is typical of a more competitive, quantity over quality mentality. It is true that of those NDs I met, fewer seemed obsessed by sex and can appear quite shy in these matters.
    Yet, when it comes to relationships between NDs & NTs, it has to be recognised that it is very difficult to enjoy love, understanding & sex with a person possessing fundamentally different attitudes to ourselves with which it is not easy to communicate.
    Between ourselves, I have observed a little more success in the field, though' because of our individuality, it always represents a challenge. The temperament of the ND can also be quite different sexually from that of the NT.

    The point is, on every level, our minor genetic differences can interact quite massively with our lives. The modern world, being so fast & challenging & extremely hide bound in convention is problematic, much as it would be on the lives of more ancient peoples. Scientists are finding increasing evidence that Neanders were a sophisticated people with the power of speech & not primitive brutes. In my opinion, differently hard wired brains, not caused by accidental brain damage must be a result of genetic differences passed on by alternative types of humans. Far from having a mysterious genetic abnormality, we are as we are because we were genetically designed to be that way..

    ReplyDelete