Could Asperger's Really Be a Legacy of the Neanderthals?

There are many theories for what the causes are of conditions like Asperger's, ADHD or Tourette. A controversial but intriguing theory called the Neanderthal theory of autism offers a unique perspective of this neurodiversity as a fully functional human variation.

The Neanderthals (Homo Neanderthalensis) are our closest human relatives and lived in Eurasia 200,000 to 30,000 years ago. Their appearance was similar to ours, but they were shorter and stockier with angled cheekbones, prominent brow ridges, and wide noses. Though sometimes thought of as dumb brutes, scientists have discovered that they used advanced tools and art, were familiar with language and symbols, buried their dead, controlled fire and so forth.

Genome sequences harvested from Neanderthal bones have recently confirmed that Neanderthals and modern humans (Homo Sapiens) mated, and that 1% to 4% of the genomes of people who descend from Europeans, Asians and other non-Africans is Neanderthal. This crossbreeding went on for several thousands of years during the period when modern humans from Africa were (re)-populating the world around 40.000 years ago, until the Neanderthals disappeared from the scene.

Their genes probably helped us adapt to the colder climates in the north, but according to the Neanderthal theory of autism, those genetic influences may also manifest as Autistic Spectrum Disorder (ASD), which is the name for a range of similar conditions, including Asperger syndrome, that affect a person's social interaction, communication, interests and behavior. However, the hypothesis is far from proven and one of the first questions one might ask is: as sub-Saharan Africans don't have Neanderthal DNA, is ASD less common in them than it is in Europeans?

Although comprehensive data is lacking, the answer seems to be yes. In 2011, a study was done in Sweden which specifically looked at risk factors for ASD in relation to perinatal factors and migration. Among children of women who were born in sub-Saharan Africa only 1 case of Asperger's was recorded, but the risk for the more classical form of autism (the more well-known form that is associated with lower intelligence) was found to be relatively high with 11 cases found. Among Europeans, in contrary, Asperger's and autism were much more evenly spread.

People with ASD differ from each other just as much as anyone else, and their condition should not be seen as a disability, but rather as a slightly different way of functioning. It's usually characterized by the ability to focus on one interest or task, along with little flexibility for change and a high sensitivity to stress.

It's more common in boys and manifests itself as a different development towards adulthood, which leads to being ahead of age when it comes to cognitive skills, but lagging behind in social and emotional terms. The level of intelligence is normal, but IQ tests may show a disharmonic profile, which means being very good at one thing but really bad at another.

Despite a normal development of language there are severe difficulties in social interaction which often lead to exclusion and rejection. The use of language is sometimes peculiar and words or remarks are often taken literally, while non-verbal communication poses difficulties.

This might be caused by a different way of using "theory of mind" or "cognitive empathy." In order to have an efficient and satisfactory conversation, people continuously form a (subconscious) image in their minds of what the person they're talking to might be thinking and feeling. In the case of autistic spectrum, this system doesn't work as quickly, or might get overloaded by all the signals that we are constantly broadcasting when having a conversation, many times contradictory and confusing.

People in the autistic spectrum are usually more sensitive to sensory perception, such as the smell of a scent. Looking at a Neanderthal skull with its large space for the nose, it's not hard to imagine that they might have had a better sense of smell, too. Their heads were also bigger than those of modern humans, which could indicate a very good memory, a property Asperger's are known for as well. However, bigger brains come with a price which is larger internal distances to be bridged by the neurons, possibly resulting in less interconnectivity within the brain.

To determine whether the Neanderthal theory of autism is valid, more research to identify Asperger's genes and find out when and how those genes developed in humans would have to be done. Meanwhile, we must be grateful and regard ASD as part of the diversity that Mother nature needs, in order to produce this beautiful world in which we live.
(May 2016)