Troy Hubbard, Ph.D candidate in molecular biology, left, reviews as chart of proteins collected from a sample with Dr. Gary Perdew in their Life Sciences Lab at Penn State. The researchers are part of a team that examined whether a genetic mutation that is now ubiquitous in humans increased our tolerance to smoke, leading to an evolutionary advantage over other hominins, such as Neandertals. Image: Patrick Mansell

Where there's smoke and a mutation there may be an evolutionary edge for humans

UNIVERSITY PARK, Pa. -- 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.

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.

"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, 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, Neandertals 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.

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