If you feel more pain sensitivity than others, blame your Neanderthal genes

The genetic blueprint of modern humans is an amalgamation of ancestral ties, encompassing contributions from various ancient populations. Among the most intriguing revelations from genetic research has been the discovery of the extent to which Neanderthals have influenced the genetics of contemporary Homo sapiens. New research co-headed by researchers from University College London (UCL) has thrown new light on this intricate web of genetic connections, specifically focusing on the sensitivity to certain types of pain.

Studying pain sensitivity

The study unveils the influence of three Neanderthal-derived variants in the SCN9A gene, which is crucially involved in sensory neurons. These variants make carriers more sensitive to the sensation of pain following skin pricking after exposure to mustard oil.

Historically, three variations in the SCN9A gene, labeled M932L, V991L, and D1908G, have been identified in the sequenced genomes of Neanderthals. Past studies have documented heightened pain sensitivity in humans who possess all three of these variants. Yet, until this study, the precise sensory responses influenced by these gene variations remained shrouded in mystery.

Methodology and findings

The research collaboration comprised teams from UCL, Aix-Marseille University, University of Toulouse, Open University, Fudan University, Oxford University, and was part-sponsored by Wellcome. Their primary method involved evaluating the pain thresholds of 1,963 participants from Colombia using varied stimuli.

The SCN9A gene encodes a sodium channel, prominently expressed in sensory neurons, that interprets signals from injured tissues. The study identified the D1908G variant in approximately 20% of chromosomes within the Colombian cohort. Remarkably, about 30% of the chromosomes with the D1908G variant also carried the other two (M932L and V991L) variants.

Key findings of the research indicated:

• The trio of variants was tied to reduced pain thresholds when exposed to skin pricking post mustard oil exposure.
  
• This reduced pain threshold was absent in response to heat or pressure stimuli.
  
• The collective possession of all three variants heightened pain sensitivity compared to the possession of just one.

Furthermore, the study’s expansive genetic data analysis of 5,971 individuals from regions across South America revealed a higher prevalence of these Neanderthal variants in populations with a significant proportion of Native American lineage.

Theoretical implications

The authors propose that these Neanderthal-derived gene variants might amplify the sensitivity of sensory neurons by tweaking the nerve impulse generation threshold. Intriguingly, the team hypothesizes that such variants might be predominant in populations with pronounced Native American ancestry due to chance occurrences and genetic bottlenecks during the initial human settlement of the Americas.

It’s crucial to consider the evolutionary advantages or disadvantages of these variants. While short-lived, intense pain can guide behavior, steering individuals away from further injury, it remains a mystery whether higher pain sensitivity offered any evolutionary benefit.

Pain sensitivity as a survival trait

Dr. Kaustubh Adhikari, co-corresponding author from UCL Genetics, Evolution & Environment and The Open University, had earlier highlighted how Neanderthals have impacted the shape of the modern human nose. Commenting on the study, Dr. Adhikari remarked, “Pain sensitivity, a paramount survival trait, allows us to eschew harmful stimuli. The data suggests Neanderthals might have been more attuned to specific pain types. Further exploration is needed to grasp its evolutionary implications.”

Dr. Pierre Faux from Aix-Marseille University and University of Toulouse, the study’s first author, emphasized the multifaceted nature of pain perception, which is influenced by a plethora of factors, ranging from genetics to environmental conditions.

As humanity endeavors to understand its complex genetic past, the revelation of Neanderthal contributions to pain sensitivity offers a fascinating glimpse into our shared history. Further research in this direction can unlock more secrets about the role of these ancient genes in the fabric of modern human evolution.

The full study was published in Communications Biology.

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