Autism was added to the growing list of things we inherited from Neanderthals

We know that present-day Europeans and Asians have inherited between 1.5% and 4% of Neanderthal DNA, but how does this seemingly small amount of ancient genetic material affect modern physical and mental health?

A new study by researchers from Clemson and Loyola Universities, located in South Carolina and New Orleans, respectively, examined genetic traits that modern humans inherited from Neanderthals and, for the first time, found a link to autism.

“This is the first evidence that I’m aware of that Neanderthal DNA is linked to autism,” said Alex Feltus, a professor in Clemson’s Department of Genetics and Biochemistry.

Neanderthals (Homo neanderthalensis) are a separate species and not the direct ancestors of modern humans (Homo sapiens). However, genome analysis has shown that they did interbreed, albeit to a limited degree. The small percentage of Neanderthal DNA found in Eurasian populations suggests that both species arose after modern humans left Africa but before they spread to Asia and Europe. Previous research has linked this genetic inheritance to neurological, psychiatric, immune system and skin conditions.

For the current study, researchers took data from publicly available databases to see if Neanderthal DNA was enriched in autistic people and their unaffected siblings compared to ethnically matched controls. They looked at single nucleotide polymorphisms, or SNPs (pronounced “snips”), the most common type of genetic variation among humans. Each SNP represents a change in a single building block of DNA, called a nucleotide. When SNPs occur within a gene or in a regulatory region near a gene, they may play a role in disease by affecting its function.

The researchers’ analyzes identified 25 SNPs associated with brain development that were significantly enriched – that is, overrepresented – in people with autism. However, these Neanderthal-derived variations will not always result in autism, the researchers said. Instead, it’s about sensitivity to the condition.

“The hypothesis is not, ‘Did Neanderthals give us autism?'” Feltus said. “It’s that Neanderthals gave us some of the gene changes that give us a higher susceptibility to autism. Autism is a complex trait. It is controlled by many, many genes. A big part of what we do in my lab is trying to understand the level of complexity. Of the 60,000 genes in the human genome, how many genes are at play when you develop autism or cancer or some other complex trait? We embrace complexity. We don’t try to hide the complexity.”

The researchers hope their study will lead to further research into the ongoing influence of ancient, Neanderthal-derived genes on modern brain development, intelligence and overall human health, including gaining more insight into the complexity of autism.

The study was published in Nature JOURNAL Molecular psychiatry.

Source: Clemson University