A genetic mutation may have helped modern humans adapt to smoke exposure from fires and potentially sparked an evolutionary advantage over competitors such as Neanderthals.

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.

The mutation may have offered ancient humans a sweet spot in effectively processing some of these toxins — such as dioxins and polycyclic aromatic hydrocarbons — compared to other hominins.

The researchers, who released their findings in the current issue of Molecular Biology and Evolution, suggest that a difference in the aryl hydrocarbon receptor — which regulates the body’s response to polycyclic aromatic hydrocarbons — between humans, Neanderthals and other non-human primates may have made humans more desensitized to certain smoke toxins. The mutation in the receptor is located in the middle of the ligand-binding domain and is found in all present-day humans, Perdew added.

Ligands are small molecules that attach to receptor proteins in certain areas in much the same way that keys fit into locks.

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