From the cave to bedside: Does it matter if patients have Neanderthal DNA?

The proliferation of ‘discover your DNA’ companies led to a huge global business and a craze among people desperate to find their distant roots. As you read this, millions of gallons of saliva samples are winging their way to commercial labs all over the world, mostly in the US and Europe. On top of that, at-home DNA testing kits gained traction in recent years and probably caused a couple of family arguments along the way. One of the more popular appeals of these tests has been to establish whether or not a person has Neanderthal DNA within them. But if they do, does it matter, and does it make them more susceptible to some conditions?

A study from 2024 by folks at the University of California, Berkeley, updated our understanding of Neanderthals, and specifically how they coexisted with homo sapiens in Europe and Asia. Specifically, Neanderthals interbred with modern humans, starting about 50,500 years ago and lasting for about 7,000 years, at which point Neanderthals began to disappear. This has resulted in a small amount of us inheriting many genes from our Neanderthal ancestors, which in total make up between 1 to 2 per cent of our genomes today.

Also living alongside and interbreeding with homo sapiens were Denisovans, another species of early human who lived in Asia and were distantly related to Neanderthals. Much less is known about Denisovans, as their fossils have been harder to come by than Neanderthals.

But does any of this matter today, and if so, why? There is a flurry of studies with counterpoints – some say genetic variations inherited from these hairy ancestors may play a part in our height, hair texture, sensitivity to smell, immune responses, adaptations to altitude, and other traits. Some research suggests these genetic variations may influence our chances of developing certain diseases.

The research is ongoing. In a 2023 paper in Molecular Biology and Evolution, the authors suggest “the present meta-analysis identifies 61 independent genetic risk variants associated with Dupuytren’s disease. We find that the second most important genetic risk factor located on chromosome 7, which confers an odds ratio of ∼1.8 (P = 6.4 × 10-132… is of Neanderthals origin.”

Apart from Dupuytren’s disease, it has also been suggested that ancient human DNA may influence physical features. In a 2023 paper in Nature Briefing, the authors write how “genetic determinants of variation in facial features in contemporary human populations are also likely to have played a role during the evolution of facial morphology. We previously identified a region… in which a tract introgressed from archaic humans (Denisovans) impacts on lip thickness. That chromosomal region had previously been shown to be associated with body fat distribution and bears a strong signature of natural selection, raising the possibility that Denisovan introgression could have facilitated adaptation to a cold environment.”

A 2016 study in Science went much further in suggesting a link between ancient DNA and the risk of developing some conditions. Titled ‘The phenotypic legacy of admixture between modern humans and Neanderthals’, the research “discovered and replicated associations of Neanderthal alleles with neurological, psychiatric, immunological, and dermatological phenotypes”. Neanderthal alleles explained a significant fraction of the variation in risk for depression, the authors wrote, as well as skin lesions resulting from actinic keratosis. Individual Neanderthal alleles were significantly associated with specific human phenotypes, including hypercoagulation and tobacco use, they stated.

The increased blood coagulation, they wrote, may have helped our ancestors to deal with new pathogens as they moved to different environments by sealing wounds more quickly. Of course, we all know the dangers of hypercoagulation in the modern setting.

These studies no doubt sent some members of the public into a tizzy, and some have presented at clinics clutching their home DNA test results and a copy of a study, breathlessly demanding some kind of prophylaxis. Having said that, the popularity of DNA testing is showing some decline. Market saturation and privacy concerns are just two reasons for this, but perhaps most importantly, many of these test results aren’t as accurate as people like to think.

Move over rollerblades and fidget spinners – unless it begins to serve some useful purpose, ‘discover your DNA’ testing is probably destined for oblivion.

Last word to the National Institutes of Health, which is also looking at the impact of ancient species’ DNA on modern humans: “Having more or less DNA in common with archaic humans says nothing about how ‘evolved’ a person is, nor does it give any indication of strength or intelligence. For now, knowing which specific genetic variants a person inherited from Neanderthal or Denisovan ancestors provides only limited information about a few physical traits.”