A genetic mutation may have helped modern humans adapt to smoke exposure from fires and perhaps sparked an evolutionary advantage over their archaic competitors, including Neandertals, according to a team of researchers. Modern humans are the only primates that carry this genetic mutation that potentially increased tolerance to toxic materials produced by fires for cooking, protection and heating, said Gary Perdew, the John T. and Paige S. Smith Professor in Agricultural Sciences, Penn State. At high concentrations, smoke-derived toxins can increase the risk of respiratory infections. For expectant mothers, exposure to these toxins can increase the chance of low birth weight and infant mortality. “If you’re breathing in smoke, you want to metabolize these hydrophobic compounds and get rid of them, however, you don’t want to metabolize them so rapidly that it overloads your system and causes overt cellular toxicity,” said Perdew.
The researchers used computational and molecular techniques to examine the difference in the genetics of polycyclic aromatic hydrocarbon tolerance between humans and Neandertals. They examined a genomic database of humans, Neandertals and a Denisovan, a hominin more closely related to Neandertals than humans. “We thought the differences in aryl hydrocarbon receptor ligand sensitivity would be about ten-fold, but when we looked at it closely, the differences turned out to be huge,” said Perdew. “Having this mutation made a dramatic difference. It was a hundred-fold to as much of a thousand-fold difference.”