Some people flinch at a needle prick faster than others. One possible reason, at least in a very specific experimental setting, may be old—very old—DNA.

In a 2023 paper published in Communications Biology, researchers linked three Neanderthal-derived variants in the gene SCN9A to a lower threshold for one kind of pain test in modern humans: a skin-pricking test performed after the area had been sensitized with mustard oil.

“We have been learning more and more about what we have inherited from [Neanderthals] as a result of interbreeding tens of thousands of years ago,” Kaustubh Adhikari, study co-author and University College London Genetics, Evolution & Environment researcher, said in a statement. “Our findings suggest that Neanderthals may have been more sensitive to certain types of pain, but further research is needed for us to understand why that is the case, and whether these specific genetic variations were evolutionarily advantageous.”

But pain isn’t just one switch in the body. Heat, pressure, inflammation, a pinprick, chronic pain, and a nagging bad tooth don’t all run through the exact same doorway. This study dealt with a controlled lab measure, not a sweeping explanation for why one person shrugs off pain and another hates the dentist.

Since researchers first sequenced the Neanderthal genome, scientists have spent years looking for the places where archaic DNA still shows up in living people. Some of those links are stronger than others. And a March 2026 methods paper in Molecular Biology and Evolution sharpened the warning label: conclusions about specific Neanderthal-derived regions can shift depending on which introgression map researchers use.

In the pain study, researchers investigated three Neanderthal-linked changes in SCN9A—M932L, V991L, and D1908G. The gene helps build Nav1.7 sodium channels, which nerve cells use as part of the body’s pain-signaling machinery. People carrying all three variants showed the clearest association with greater sensitivity in the skin-prick test, though the paper also found evidence suggesting that fewer than three variants may still matter.

Authors say that the three gene variants were associated with a lower pain threshold for pricking the skin after earlier exposure to mustard oil (which was used to sensitize the area), but were not associated with any changes in tolerance for pain caused by heat or pressure. The clearest signal appeared in people carrying all three variants, but the authors did not frame the effect as an all-or-nothing switch.

The same sodium channel had already drawn attention in 2020, when researchers from the Max Planck Institute for Evolutionary Anthropology and Sweden’s Karolinska Institutet linked the Neanderthal version of Nav1.7 to greater self-reported pain in present-day people. That earlier work helped set up the 2023 study, but it came with a problem: the variants are rare in Europeans, making broad claims from those data harder to nail down.

The 2023 paper dug into a more specific question: are those variants tied to mechanical pain after chemical sensitization of the skin? The answer was yes—in that test. Heat and pressure didn’t show the same association. But the mechanism is still messy. The paper says the functional evidence varies by experimental system, and the strongest regional signal in its own analysis involved non-coding segments, leaving open the possibility that regulatory DNA near the three coding changes is part of the story.

“We have shown how variation in our genetic code can alter how we perceive pain,” Pierre Faux, first author and researcher at Aix-Marseille University and University of Toulouse, said in a news release, “including genes that modern humans acquired from the Neanderthals.”

The study looked at admixed Latin American cohorts, with pain testing in healthy Colombians and broader genetic analyses across people from Brazil, Chile, Colombia, Mexico, and Peru. The variants were more frequent on Native American ancestry haplotypes, with the highest frequencies in Peru, where Native American ancestry was highest in the study.

The team now wants to know if this lower pain threshold offered up any sort of evolutionary benefit, or if increased pain sensitivity when poked is just another piece of Neanderthal history living in modern humans.