By Nabeeha Anis
Neanderthals are an extinct species of archaic humans that lived in Eurasia around 40,000 years ago. Both Neanderthals and humans coexisted together for around 5,400 years, and scientists have discovered that “past interbreeding with Neanderthals” has influenced the genome of modern humans. Small bits of Neanderthal DNA have been passed down from generation to generation, and some of the many modern humans that carry this DNA have been affected by certain mutations. In a recent study by an international team (University College London, Oxford University, Fudan University, etc.), scientists discovered that people with three gene variants (inherited by Neanderthals) in the SCN9A gene have greater pain sensitivity than others.
The SCN9A gene encodes a sodium ion channel called Nav1.7 to regulate neuron excitability in both normal and pathological pain states. Nav1.7 is expressed at high levels in the sensory neurons that detect pain receptors from damaged tissues. Nav1.7 possesses a distinctive quality known as slow closed-state inactivation, enabling the channel to react to gradual depolarizations by producing a gradual current response. These Nav1.7 channels are commonly located at nerve terminals associated with nociceptors, which are responsible for generating electrical potentials when sensory nerves are stimulated. Nociceptors are specialized nerve receptors that play a crucial role in the body’s perception of pain, so a genetic variant in the SCN9A gene encoding Nav1.7 channels would impact pain perception.
The study evaluated the pain sensitivity effects by choosing a group of people with the three gene variants of SCN9A called M932L, V991L, and D1908G and comparing their pain levels after putting their pricked skin in mustard oil. Previous research has discovered that those with Neanderthal DNA have these three genetic variants, but the actual impact it had on sensory receptors and pain responses was unclear.
The international team studied the pain thresholds of 1,963 people to study the effects of these genetic variants. 20% of the representative sample had the D1906G genetic variant and 30% had the V991L and M923L genetic variants. Those who carried all three of these variants experienced greater effects of pain sensitivity than those who didn’t. The researchers believed that Neanderthal variants can affect sensory neurons by changing the threshold at which a nerve impulse is generated. There is a clear importance of Neanderthal introgression in the modern human genome. Other genetic variants have been discovered in the past relating to our body’s immune systems and metabolisms.
More research has to be conducted in order to discover whether or not these genetic variants were advantageous throughout evolutionary history in any way. The reason why Neanderthals had greater pain sensitivity than modern humans is unknown, and evolutionary scientists hope to find out why.
Image Credits: Courtesy of Science Photo Library
Bibliography:
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University College London. "Neanderthal gene variants associated with greater pain sensitivity." ScienceDaily. ScienceDaily, 10 October 2023. <www.sciencedaily.com/releases/2023/10/231010182939.htm>.
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