The Neanderthal theory of Autism

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Ah, thanks for the clarification RDOS. I admit I don't know much about this research, but I'll probably look into it more in the future. I don't have any background in genetics, so I'll only understand it in a purely psychological sense.



I would beg to differ. This validity of this explanation depends on whether one believes that autism is an evolutionary adaptation. I see what your saying though, that your argument is consistent with the Neanderthal Theory of Autism.

At my current stage of research, I don't believe that autism is an evolutionary adaptation but rather a disorder, a defect. A large part of the psychology community agrees with me.

One could argue, from a "defective" rather than "adaptive" standpoint that many impairments exist at a high prevalence, such as those seen in Schizophrenia, which affects approximately .55% of the population. Most schizophrenics don't reproduce, but the genes are passed on by carriers. Similar to the way carriers of red-blood-cell diseases pass on the full-blown disease. (Yes I know it is much more complicated than that with mental disease, since red-blood-cell diseases only affect one gene on each chromosome.)

Why do we need to "explain" how disabilities can be retained by evolution? Why is any congenital and/or genetic disability retained by evolution, for that matter? Mental retardation, muscular dystrophy, Huntington's Disease, cystic fibrosis...none of these can be easily "explained away." Why should autism be any different? (Now, I personally believe that there are advantages to ASCs, unlike those other conditions, but I don't pretend that the fact that the condition has survived is sufficient proof of this.) You say that autism is relatively "common" (at least in certain areas), but that's something of a subjective value judgment. .5% of the population or so (diagnosed) isn't really that common. Besides, there are plenty of maladaptive traits which are common, such as correctable vision problems.

I don't pretend to be an expert in evolutionary biology, but it seems to me that you err in assuming that evolution is at some kind of end point. It's really not. The process is not nearly as efficient in weeding out "imperfections" as you seem to think.

Here's my evolutionary model of autism. The human population benefits and has always benefited from having some of its members exhibit autistic traits to varying degrees. Such individuals likely made disproportionate contributions to technological progress, gaining social respect, hence insuring that some autistic people remained in the gene pool. This continues to the present day. (Not that autistic people need to make special contributions to reproduce, necessarily.) Other traits which autistic people tend to have, such as an attention to detail, great memory, ability to devote a great deal of time to one task, amongst others, also were likely valuable in our evolutionary past, just as they continue to be valuable today. It can be reasonably inferred that some autistic people were in fact able to become valuable members of their communities due to these traits in spite of their other disabilities.

Why you seem to think that only the Neanderthal hypothesis can "explain" autism is really beyond me.

Aha, Neanderthal of the gaps theory now is it?

Genetic drift, relative advantage of the heterozygous state, the condition is the result of environmental factors, the condition arises as the result of mechanical error in the production of sex cells, the condition requires multiple genetic triggers entailing genes that outside particular configurations are neutral or advantageous, responsible genes are not dominant and are closely linked to advantageous genes, some admixture of factors entailing two or more the proceeding.

Explain why they could or should not be, or even what "personality traits" you are on about.


Provide a reason why there needs to be such a model.

No matter how much easier it might be to criticize an idea than to provide one, it is still wiser to not believe ideas that appear far-fetched, and for which there does not appear to be any substantive argument for.

What a pathetic non-argument. Neanderthal of the gaps....

Let me ask you, why on earth any trait inherited from Neanderthalic ancestors, that has the effects that ASDs have, would not have been selected out by the same mechanism, you think would select out these traits if they were not caused by Neanderthal ancestors? Does the Neanderthalic-gene fairy Godmother protect these particular genes from the usual evolutionary processes?

Well put. If autism is not an evolutionary adaptation, then there need not be an evolutionary model, only the "disorder model" that we already have.

If we compare it to mules (crosses between equines and donkeys) we can say such hybrids were most likely sterile.

Hee hee but if such hybrids weren't and reproduced with each other chances are they make up part of the Land of the Lost cast.

Okay I have a bit of a duplicitous theory here. Bear with me. What if... what if the people who created those Chaka characters in Land of the Lost are the ones who came from the Neanderthal/Cro-Magnon hybrids and that's how the idea of Chaka came about? It's because of the tiny fragments of Neanderthal DNA in their cells and it caused them to have Chaka recognition so they came up with the Chakas?

The answer to my question seems speculative, at best. First, none of us lived there then, so we don't have first hand personaly knowledge. But it seems to me if a hybrid had a Neanderthal brain that was autistic-like, then there would seem to be acceptance with the pure-Neanderthals -- they would be on the same wavelength in thinking.

If hybrid had Neanderthan brain that was autistic-like and was with pure humans, would seems to me to have all teh same brain-relating problems we see now with autistic when we try to relate to neurotypicals -- out of sync. But, there might be pure-human acceptance of the hybrid with the autistic brain when the pure humans discovered the hybrid had some useful abilities not possessed by the pure-humans that helped the pure-human social group.

Just what I think, but feel free to refute my theory...

apologies for the typos -- was inadvertent

Why on earth would the hybrid have an autistic like brain? There is a problem with this theory and that is even if you were correct, this still would not result in Neanderthal DNA ending up in our gene pool.

Putting aside any issues of "brain-relating problems" there is the earlier problem of the morphological condition of the hybrid. There is no reason to assume that this hybrid would have had any particular useful abilities.

I would just like to point out that these quotes of "mine" are sentences I quoted from the Neanderthal article, which is why I used "..." around them.



@ rdos: Asexuality is a sexual orientation. Excerpt from wikipedia: "Asexuality is a sexual orientation describing individuals who do not experience sexual attraction or do not have interest in or desire for sex. Sometimes, it is considered a lack of a sexual orientation. One commonly cited study placed the incidence rate of asexuality at 1%"
http://en.wikipedia.org/wiki/Asexuality

Not to us in contemporary society. But in the past people have killed or abandoned children that were seen as not "quite right". Even when they weren't seen as changelings, they weren't deemed to be worth the effort. To most people food was scarce and these children were not a priority. It was better to use resources on what was seen as strong offspring that would pass on the genes (or to their mind, inherit the farm/family name etc).

Animals always leave behind their offspring when something isn't right about them. Females of some species (like mice, I think, or was it mink) can also resort to cannibalism and eat their offspring if they are disturbed/the nest doesn't seem safe for some reason. It gives the female strength after the birth, and gives her the chance to try again later rather than risk dying along with her young.

OK, let me clarify. Asexuality is not related to other sexual orientations, but to non-sexiual factors. Things like being homosexual, having odd sexual preferences, having different opinions about courtship & relationships and things like that are related, but they are not related to asexuality.

OK, so we have a few disorder-thinkers in the thread? Fine, you are entitled to your opinion, but IMHO, most of the recent research does not support your model of autism being an disorder. And even if it is a disorder, nobody can explain the prevelance and linkage to other (disorders) like ADD, Dyslexia and Schizophrenia. Using Scihzophrenia as an example of another "disorder" that exists at high prevalence isn't very interesting given that Schizophrenia is correlated with ASDs. The problem explaining Schizophrenia with the disorder view is exactly the same as explaining ASDs or ADD with a disorder view.

Some of the stuff in this thread is so unlikely. Why is it Neanderthals are associated with HFA traits to begin with when anyone who's read Clan Of The Cave Bear knows Neanderthals weren't motorly clumsy, were far from being verbal communicators. Most of their communication was based on reading non verbal clues. They communicated with looks and gestures which Aayla had difficulty with at first because she was Cro Magnon but quickly learned but not as naturally as Neanderthals. (because Cros are considered to be more adaptable than Neanderthals which is one reason it's speculated Neanderthals became extinct) She was considered to be worse at non verbal communication but she was better at making advanced tools and using them to hunt. Her coordination was better. She was able to make and effectively use a sling shot if I remember correctly but does this mean the Neanderthals were really motorly clumsy? A cheetah runs on four legs while a human navigates on two. Does this mean the cheetah is clumsier than the human? It's like comparing steaks to potatos.

It is possible but not probable that they reproduced with Cro-Magnon but if they did, it is unlikely their alleles are responsible for autistic traits. Far more probable is the idea that autistic alleles are that way because of bad pairing with other alleles that create a mutation. Incompatable allele pairing could be responsible for most mutations. Sometimes mutations are beneficial to a species, sometimes not. What decides if something is beneficial or not is if the species can survive with the mutation long enough to produce offspring and pass the mutation to them. This is how natural selection works and is the likely reason autism exists in human beings.

Last edited by ooOoOoOAnaOoOoOoo on 26 May 2009, 9:11 am, edited 1 time in total.

The "clan of the cave bear" isn't necesarily the truth about Neanderthals. But regardless, in my experience, autistics do not have general problems with nonverbal communication. They have specfic problems with NTs only, and can communicate quite well with other Aspies that share the differences in nonverbal communication. I think I know a lot about this after having been brought up in an Aspie-family, and now being a parent in one.

IOW, autistics do not inherit general deficiencies in nonverbal communications from Hn, they inherit Hns species-typical way to communicate, which doesn't work very well with NTs.



A general rule that regulates alelle frequencies is that alleles either goes towards fixation or gets extinct. This rule says that disordered alleles will get extinct over time. Over time, alleles that are negative for the individual will almost always get extinct. For the disorder-view, this will only leave one possibility, the mutations are recent, and therefore haven't had a chance to get extinct yet. However, this creates another problem. Recent mutations will not be linked, which practically all ASD alleles are to varying extents.