There have been numerous theories put forward to explain autism, Asperger’s Syndrome, ADHD and Tourette’s Syndrome. These theories are most compelling when applied to a narrow range of behavior or deficits. Such theories tend to fall apart or at least become less compelling when the attempt is made to widen their scope and apply them to larger ranges of behavior and deficits found on the autism spectrum. It is argued here that the fundamental problem inherent in existing theories is that they presume that individuals who present autistic and related behaviors and deficits are “disordered”, when in fact the case may be made that such individuals are fully functional. It is in the areas of cognitive and behavioral adaptations which are species-specific that autism is found, such as nonverbal communication, emotional empathy, social organization, motor skills, sensory acuteness, sexuality, physical traits and biological adaptations. It is here argued that the DNA diversity in modern humans of Eurasian descent is consistent with the introgression of Neanderthal genes into the human genome through interbreeding. Firstly, fossil record indicates humans and Neanderthals living side by side for thousands of years in these regions. Secondly, the genes positively associated with autism have now been identified in the group of genes recently introduced through interbreeding with Neanderthals. Lastly, some of the behaviors and sensitivities of those on the autism spectrum make sense in the context of a cold-adapted species such as Neanderthal.
The Evolution of Homo
The first primates were very small and they appear in the fossil record during the dinosaur era. The higher primates are thought to have evolved in Asia over 40 million years ago and subsequently to have expanded into new regions, eventually arriving all around the world. Modern humans and Neanderthals alike stem from this line of primates drawn from Oreopithecus which was an aquatic ape that lived on an isolated island in the Mediterranean near Italy some 7 to 9 million years ago, to Australopithecus who walked the plains of Africa around 3 million years ago, and finally to the archaic Homo lineages from whom emerged modern humans and modern human behavior. Homo Erectus belongs to the earliest membership of the Homo evolutionary club, and he makes his appearance at roughly the same time the ice ages began in Eurasia. In Ceprano Italy, somewhere between 800,000 and 900,000 years ago, Homo Erectus emerged to father this line of primates at around the time of the beginning of the Eurasian ice ages. His brain was larger, and it is possible that the cold climate and harsh, unstable living conditions pressured the constant adaptations required of a species to survive.
The consequences of survival pressures in a cold environment likely resulted in an endogamous, matriarchal, and group-bonded social structure within very small populations with little contact between groups. Groups may have consisted of groups of 1-3 females in reproductive age, 1-3 males in reproductive age, children, and the elderly. It is likely that the females in the group were related, whereas males were dispersed to other groups at maturity. They likely matured late and lived longer, subsisted chiefly on meat, spent winters in hibernation or near hibernation, and stored up reserves during the months of plenty. The Neanderthals emerged in Eurasia, ostensibly from Erectus, and became physically cold-adapted. It is surmised that his social structure would resemble that of the cold-adapted Homo Erectus.
In contrast to the promiscuous cold-adapted varieties of Homo, the warm-adapted ones formed monogamous pair bonds. The warm-adapted species eventually became anatomically modern humans. Selective pressures forced them to shed their fur and they lived nomadic lives in larger social groups, which promoted selection for social adaptations. Their patriarchal hunter-gatherer lifestyle included gender-based division of labor, aggression between males, male alliances, and warfare. Selective pressures would have provided the basis for ethnocentric and racist ideas. Their children matured relatively early and they could reproduce much faster. Males would be more likely to select mates from within their own group, and the overall package of social adaptations would have made their social structure similar to that of chimps in certain ways.
A fossilized hominid looking very much like an anatomically modern human was discovered in Ethiopia, and dates back to 160,000 ago. The warm interglacial period which began around 130,000 years ago would have been an open invitation to this archaic man to spread northward into Western Asia, and it is surmised that fully modern humans were the result of interbreeding events between the species found at Herto and the Erectus species he would have encountered were he to follow game into the thawing Asian continent.
At 125,000 ago there were already Neanderthals in Finland, and they covered an area from central Asia to northern and western Europe, where their cold adaptation gave them a survival advantage. As the earth cooled again and parts of Europe and Asia moved into the next glacial period, the more robust Neanderthals no doubt pushed the anatomically modern humans back down from Central Asia into Southern Asia and the Middle East. During this period, the first interbreeding between anatomically modern humans and Neanderthals likely occurred.
In modern times, the descendants of the first anatomically modern humans are the San/Bushmen of South Africa and South Asian populations. The Bantu people may represent back-breeding between anatomically modern humans and archaic African Homo. No precise date has been attributed to when the San came to Africa, but they share similarities with East Asians which implies a recent migration into Africa at around 20,000-30,000 years ago. The Toba eruption, which occurred around 74,000 years ago, resulted in the loss of genetic diversity in Asia, and the surviving population was partitioned into two groups. It wasn’t until around 50,000 years ago that these remnants had accumulated enough technical and social innovations borrowed from neighboring Neanderthals and Homo Erectus to expand into Northern Asia where temperatures were much cooler. Much later, around 35,000 ago, early modern European humans are discovered. In the study of gene transmissal, “reinforcement” is a resistance against hybrids driven by selection. Females of the rarer species often encounter this first. The prevailing wisdom is that the successful hybrid offspring would be rare, yet even a single hybrid offspring might succeed in transmitting advantageous genes into the mix. The statistically higher probability that the successful hybrid would be male leads many to think that it might be impossible to trace Neanderthal lineage through mitochondrial DNA.
Are Neanderthals a Separate Species?
Some researchers doubt whether Neanderthals and modern humans could have produced viable or even fertile offspring, and point towards the genetic separation of the two ancient lineages who were isolated for 700,000 years. However, there exist examples of other mammals which have evolved along separate and isolated lines for much longer and which yet are able to produce both viable and fertile offspring, though the relative success in each of the examples may vary. The problems met in interbreeding separate lineages do not imply that it is impossible to produce offspring, but rather that such offspring would likely suffer in terms of reproductive success. The recently decoded genome of a Neanderthal male’s thigh bone has confirmed the presence of genes compatible with the modern human genome such that 1-4% of the genetic material of non-Africans is thought to have been acquired from Neanderthals. There are also skeletal remains in the fossil record in Portugal and in Romania which some researchers believe to be examples of hybrid children.
The adaptations to the cold found in Homo Neanderthalensis evolved gradually, but are already visible to some degree one million years ago on the Iberian Peninsula. The half-million years of divergence expressed in mitochondrial DNA between Neanderthals and humans from Africa is consistent with Neanderthal’s adaptation to the cold starting before a half million years ago.
In broad regions which were shared by these distinct populations in overlapping periods over thousands of years, the archaeological evidence reveals the existence of small, isolated groups of Neanderthals and larger social networks of anatomically modern humans in Europe, Western Asia, and the Middle East. The existence of long-distance trade is confirmed among the modern human populations, but the endogamous social structure of Neanderthals requires isolation in order to function. The evidence of large social networks indicates male alliances, forged in emotional as well as practical social bonds.
There is some evidence to suggest that Neanderthals adapted to colder environments in ways not dependent on fire and cloth. In modern human settlements, a central fire with isolated shelters distributed around them are found, whereas in Neanderthal settlements, the placement of the fire is more haphazard and there is little evidence of structured activity found around them. This would suggest that Neanderthal settlements were simply patches of ground, or even nests, and were open to the elements. As Neanderthals migrated northward, there is little change seen in technological innovations, which would further suggest that their cold adaptation was physiological rather than cultural. It appears that many Neanderthals abandoned their settlements as climates worsened, indicating that their adaptation was not sufficient to cope with the harshening conditions, and indeed there is little evidence of sewing industries present in Neanderthal settlements. However, micro-wear studies of the stone tools found in Neanderthal settlements do suggest that they were used for woodworking.
The archaeological evidence tells us that Neanderthals consumed “prey” which was at the peak of its usability, which is not consistent with the behavior of other carnivores. The animals which Neanderthals “hunted” are today typically domesticable animals, and the preoponderance of the evidence is consistent with Neanderthal pastoralism. For example, their woodworking industry would be consistent with the building of fences and shelters, their skeletal remains reveal injuries consistent with those of rodeo bull-riders, they used flutes and whistles which could call animals, the domesticable animals eaten in their prime by Neanderthals appear to have “speciated” during the Neanderthal era, and it is known that Neanderthals would have required a high-protein diet to sustain their lifestyle and their massive frames.
According to some research, the type of early modern human which has been called Cro-Magnon did not originate in Europe, but in Asia. It is argued that the origin of Aurignacian industry is in Central Asia and in Eastern Europe. Modern humans in Eastern Europe began using Neanderthal technology gradually, unlike later populations of early modern humans in Western Europe. This suggests that modern humans hijacked Neanderthal technology and improved upon it.
Argument from Geography
Successful hybridization between early humans and Neanderthals would have been very rare, and the offspring of such unions would likely be back-bred into either of the parent populations, where visible traces would disappear within 3-4 generations. Caucasians, American Indians, and Asians present a statistically higher prevalence of autism than the Afro-American population, which might be expected if successful hybrids from the overlapping population zones in Western Asia expanded away from Africa. Caucasians spred from this region into the Far East, Australia, and the Americas. This hybrid genetic contribution did not make its way back into Africa apart from three notable exceptions. These three events are Neanderthal’s expansion into the Levant during the beginning of the last glacial period, the Arabic emigration from the Middle East, and European colonization. Early modern European humans show genetic evidence of a lot of inbreeding, which has been misinterpreted by some who suggest that this constitutes evidence against the possibility of fertile offspring arising from mating between them and Neanderthals. A larger variation in advantageous genes in Eurasian populations is good evidence which supports hybridization. Furthermore, these genes are local to Western Asia and Europe, and do not appear in Africa. Finally, in areas where hybridization occurred is where the record of innovation in material culture is most intensely expressed. The earliest known civilizations emerged precisely in these regions.
Music and Dancing
In Africa, music is associated with social rites and social bonding activities. This is evident still in “black” music in America, where music is used as a backdrop to the main theme of social relations. Complex instruments and music typify non-African music. The human voice and drum are the main instruments in African music, while the dances and music outside of Africa are more aimed at creativity and perfection. As far back as 100,000 years ago, Neanderthals were using phalange whistles, and flutes and whistles are found in abundance in association with Neanderthal artifacts from the Crimea, to Libya, and then in Divje Babe. The forms of flute and whistle found in the fossil record seem to have been slowly and steadily evolving until recently. It is likely that they originated with Neanderthals, but were adopted by anatomically modern humans or hybrids. It seems probable, considering the rest of the their suite of behaviors, that Neanderthals used them to herd livestock. In today’s herding societies, the tradition continues.
Medicine and Plant Use
In the Neanderthal burial site found in Shanidar, Iraq, a set of plants with medicinal applications was recovered. Among the plants found there were:
- Muscari, which has been historically used to hide the human scent from prey.
- Althea, which has anti-inflammatory properties.
- Senecio, which retards bleeding and relieves menstrual cramps.
- Achillea, which is an anti-diarrheal.
- Centauarea, a stimulant.
- Ephedra, a stimulant used for psychoactive purposes. May have been used to artificially increase Neanderthal’s activity level.
Age and Maturation
Neanderthal children would have matured late, perhaps reaching full maturity as late as age 36. Additionally, Neanderthals would have lived relatively long lives; perhaps up to 100-150 years old. Slow ear development could be explained by a preference by Neanderthals for processing visual information more than verbal information, an assumption supported by the pronounced size of the Neanderthal visual cortex compared to that of anatomically modern humans. Neanderthal’s sloping forehead is best explained by his less advanced social system.
Genes of Special Interest
Throughout prehistory and even in the present, there have been great population bottlenecks, the greatest of which would have been the eruption of Toba in Indonesia around 74,000 years ago. The fallout from this catastrophic volcano eruption resulted in a worldwide fall in temperature of 3-5 degrees centigrade for years. Africa would remain the least affected, whereas the populations in Europe and Asia would have been greatly distressed and depopulated. The next major bottleneck primarily affected Europe during the last glacial maximum around 20,000 years ago, leaving populations who arrived in the Iberian Peninsula during the Neolithic relatively unaffected. The last major bottleneck exists today for the world’s remaining hunter-gatherer populations who are being displaced by farmers in various regions worldwide. These bottlenecks explain the largest genetic diversity in Africa and the smallest in Europe.
Historical bottlenecks in population densities necessitate the use of nuclear DNA for obtaining mitochondrial DNA and Y chromosomes, since nuclear DNA has larger effective population sizes. A study of Neanderthal nuclear DNA indicates that their lineage speciated around 706,000 years ago, and that introgression of Neaderthal DNA into anatomically modern humans would have occurred around 34,000 years ago.
Small differences are present between the mitochondrial DNA of Neanderthals and modern humans, yet in a study which included 700 Eurasians and 240 Africans, all but one of the modern mutations found in their DNA were found in the mitochondrial DNA belonging to the youngest Neanderthal sample recovered in Russia. Interestingly, the older Neanderthal samples were more dissimilar to the modern human control samples, which is compatible with the hybridization theory.
Another study of modern humans finds Y-chromosome mutations occuring over 100,000 years ago, and which are not found in Africa. This is strong evidence for gene flow between modern humans and other archaic lineages, such as Neanderthals, Erectus, or both.
The gene known as PDHA1 shows two distinct classes or types. One of these types exists both inside and outside of Africa, but the other does not occur in Africa. The African version shows greater diversity, and the non-African version appears to have introgressed around 50,000 years ago. The common ancestor of both of these classes is over one million years old.
This condition affects Caucasians higher than any other group, and is thought to have emerged at least 40,000 years ago in Ireland with a single ancestor. Hemochromatosis is a condition echaracterized by the accumulation of iron in the tissues, and the treatment for this condition is actually to lose blood. The close-quarters and confrontational style of hunting employed by Neanderthals would have resulted in bloodletting with some regularity, and therefore an adaptation which promotes more efficient iron absorption might be advantageous.
Factor V Leiden
This gene introgressed in populations in Northern Europe from 35,000-40,000 years ago. However, this time frame is incompatible with the record of modern human habitation, and it is concluded that it must have originated in Neanderthals.
This gene is only found on a haplotype common in Europe, North Africa, and the Middle East, and it has been dated back to 10,000-25,000 years ago. This may be explained by a hybridization event occurring in Europe, whereupon it was subsequently transmitted to the Middle East and North Africa during the emigration out of Europe at the height of the last ice age. This gene is also associated with iron transport. Hybridization might have broken the gene complex, resulting in tissue damage due to oxidating free radicals.
ADHD – DRD4 VNTR
The gene complex associated with ADHD consists of two alleles – 4R and 7R. Both alleles are thought to be ancient, yet the estimated time of introgression for 7R is 30,000-50,000 years ago. This is consistent with the hybridization timeline.
This is a very diverse genetic condition which emerged in the modern human genome 50,000 years ago in Europe. It is in some ways similar to Celiac and may be related to gluten intolerance. It is conjectured that the purpose of Cystic Fibrosis might have been a defense against infection and parasites. This disease is often associated with high levels of salt in sweat.
RH negative blood is rare in native Americans, Asians, and Africans. However, it is found in 15% of Caucasians and possibly over 25% of the Basque population. If a new mother having a negative RH factor produces a fetus with RH positive blood, she will have potentially lethal autoimmune problems. This would have formed a barrier against back-breeding into the Neanderthal population. Over 50% of people with schizophrenia possess a negative RH blood factor, and there is a similar correlation with autism and Asperger’s Syndrome.
Skin Color, Hair Color, Freckles, Eye Color
The results of an ongoing survey distributed by the author of theory, in the form of a quiz, indicate a correlation between autism and red hair. Red hair and auburn hair are related to 3 mutations in a gene complex known as MC1R, and the mutations appear to be 50,000-100,000 years old. It is argued here that these traits were introduced by interbreeding with Neanderthals. The same quiz results indicate a strong correlation between autism and brown or hazel eyes. The MC1R appears to show that the last major change in pigmentation occurred around 1.2 million years ago; a period of time when there may have been as few as 14,000 breeding individuals. Human beings have been hairless at least since this time, which fits with the time of speciation between warm and cold adapted species. Nakedness was the beginning of a diverging evolutionary path between cold and warm adapted humans.
This European genetic defect bears a sharp diagnostic resemblance to autism.
This disease originated in Western Europe, and is rare in Asians and in Africans. Interestingly, this disease protects against cancer and infectious diseases. If present in Neanderthal along with complementary alleles to guard against its adverse effects, it would go a long way towards explaining the long Neanderthal life span. It is conceivable that it may have played a role in allowing Neanderthals to hibernate.
Another condition with a higher presence in people of European descent.
This disease is also more highly represented in people of European descent, and its frequency increases along with latitude.
IgA, Celiac, Autoimmune Diseases, and Autism
Low levels of IgA are present in autoimmune diseases such as Celiac. Studies also confirm that individuals with autism have low levels of IgA. This condition is also known as gluten-intolerance, and its distribution in the population is also mostly within people of European descent. Neanderthals were carnivores, and did not have complexes for processing the gluten found in grains.
Some portions of this theory have been omitted for brevity. The reader is encouraged to read the source material directly for more details.
Ekblad, Leif. “The Neanderthal theory of autism, Asperger and ADHD.” www.rdos.net. N.p., 24 Apr. 2001. Web. 4 June 2010. <http://www.rdos.net/eng/asperger.htm>.