A new genetic study conducted by researchers from Leiden University and Wageningen University thoroughly debunks previous claims that a genetic mutation gave early Homo sapiens an evolutionary advantage over Neanderthals in adapting to campfire smoke exposure.
Aarts et al. observe no significant difference between Neanderthal and modern human AHR.
“Making and using fire is regarded as one of the most significant innovations in man’s evolution,” said Dr. Jac Aarts, lead author on the current study, and colleagues.
“Fire brought with it such benefits as warmth, for example, protection against predators and a broader diet because it made it possible to cook raw, inedible foods.”
“A disadvantage of fire is that it exposes people to the toxic substances in smoke,” they added.
In 2016, Pennsylvania State University researchers looked at the aryl hydrocarbon receptor (AHR) gene — which regulates the human body’s response to carcinogenic polycyclic aromatic hydrocarbons produced by fires — in modern humans and Neanderthals.
They found that modern humans carry a mutation in the AHR gene that increased their tolerance to smoke-related toxins.
They concluded that Neanderthals were up to 1,000 times more sensitive to these toxins than modern humans.
In 2018, Dr. Aarts’ team came to the opposite conclusion, based on an analysis of 19 relevant genes in Neanderthal, Denisovan, prehistoric and extant anatomically modern human genomes.
They found that Neanderthals had more gene variants that better neutralized the harmful effects of toxins than most modern humans.
In the new study, Dr. Aarts and co-authors repeated the earlier experiments of their colleagues from Pennsylvania.
Instead of rat cells, the researchers used human cells and found that there are no grounds for concluding that the AHR protein made Neanderthals more vulnerable to toxins in the smoke.
“Our results are strongly at odds with a major role of the modern human AHR in the evolution of hominin detoxification of smoke components and consistent with our previous study based on 18 relevant genes in addition to AHR, which concluded that efficient detoxification alleles are more dominant in ancient hominins, chimpanzees and gorillas than in modern humans,” they said.
Their results were published in the journal Molecular Biology and Evolution.
Jac M.M.J.G. Aarts et al. Evolution of Hominin Detoxification: Neanderthal and Modern Human Ah Receptor Respond Similarly to TCDD. Molecular Biology and Evolution, published online November 24, 2020; doi: 10.1093/molbev/msaa287