Genetic mutation helped early humans use fire

A genetic mutation might have helped present day humans better handle smoke from fires, possibly giving them an evolutionary advantage over Neanderthals and other hominin species, according to a new study in the journal Molecular Biology and Evolution.

Modern day humans are the only primates with a genetic mutation that offered a heightened ability to tolerate toxic materials generated by fires for cooking, protection, and heating. At high levels, smoke-derived toxins can raise the potential risk of respiratory infections. For pregnant women, experiencing  these toxins can raise the possibility of low birth weight and infant death.

The mutation may have provided ancient humans a particularly strong coping ability for some of these toxins, compared to the coping abilities of 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,” study author Gary Perdew, a professor in Agricultural Sciences at Penn State, said in a news release.

Genetic Analysis Between Humans and Neanderthals

The scientists used computational and molecular means to study the genetics of polycyclic aromatic hydrocarbon tolerance in humans and Neanderthals. They analyzed a genomic collection of humans, Neanderthals, and a Denisovan, a hominin more tightly related to Neanderthals than humans.

The analysis indicated the gap in coping abilities may be due to differences in the aryl hydrocarbon receptor between humans, Neanderthals and other non-human primates. The mutation in the receptor is situated in the center of the ligand-binding region and is found within all present-day humans. Ligands are molecules that affix to receptor proteins in particular areas like keys that fit into locks.

“For Neanderthals, inhaling smoke and eating charcoal-broiled meat, they would be exposed to multiple sources of polycyclic aromatic hydrocarbons, which are known to be carcinogens and lead to cell death at high concentrations,” Perdew said. “The evolutionary hypothesis is, if Neanderthals were exposed to large amounts of these smoke-derived toxins, it could lead to respiratory problems, decreased reproductive capacity for women and increased susceptibility to respiratory viruses among preadolescents, while humans would exhibit decreased toxicity because they are more slowly metabolizing these compounds.”

The study could also provide support to a recent idea that says the invention of cooking may have made it easier for humans to thrive. Perdew indicated the receptor might give humans a better tolerance for tobacco smoke, putting them at risk of cancer and other serious diseases.

“Our tolerance has allowed us to pick up bad habits,” he noted.

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Image credit: Thinkstock

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