Unraveling the Evolutionary Impact of Fire: Insights from Genetic Studies
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How did the harmful effects of fire shape our evolution? It’s a question that’s just starting to attract more attention. Now, two new studies have proposed theories on how negative consequences of fire might have shaped human evolution and development. In the first, scientists identified a genetic mutation in modern humans that allows certain toxins, including those found in smoke, to be metabolized at a safe rate. The same genetic sequence was not found in other primates, including ancient hominins such as Neanderthals and Denisovans. The researchers believe the mutation was selected for in response to breathing in smoke toxins, which can increase the risk of respiratory infections, suppress the immune system and disrupt the reproductive system.
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It’s possible that having this mutation gave modern humans an evolutionary edge over Neanderthals, though it’s speculation at this point. But if the speculation is correct, the mutation may have been one way that modern humans were inured against some adverse effects from fire, while other species were not. Thomas Henle, a chemistry professor at Dresden University of Technology in Germany, has wondered whether humans also have unique genetic mutations to better handle, or even take advantage of, byproducts of fire in food. In 2011, his research group showed that the brown molecules that come from roasting coffee can inhibit enzymes produced by tumor cells, which might explain why coffee drinkers may be at lower risk for certain cancers…
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Humans may not have been able to adjust to all of the dangers of fire. The second study, published last week in Proceedings of the National Academy of Sciences, suggests that with fire’s advantageous effects for human societies also came profound new damage. It offers conjecture that the early use of fire might have helped spread tuberculosis by bringing people into close contact, damaging their lungs and causing them to cough. With mathematical modeling, Rebecca Chisholm and Mark Tanaka, biologists at the University of New South Wales in Australia, simulated how ancient soil bacteria might have evolved to become infectious tuberculosis agents. Without fire, the probability was low. But when the researchers added fire to their model, the likelihood that tuberculosis would emerge jumped by several degrees of magnitude.
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It is thought that tuberculosis has killed more than a billion people, possibly accounting for more deaths than wars and famines combined… Many experts believe tuberculosis arose at least 70,000 years ago. By then, humans were most certainly controlling fire. She and Dr. Tanaka believe that fire might have helped spread other airborne diseases, not just tuberculosis. “Fire, as a technological advantage, has been a double-edged sword,” Dr. Tanaka said. Negative cultural consequences came with fire, too — and continue to leave an imprint. Anthropologists have speculated that inhaling smoke led to the discovery of smoking. Humans have long used fire to modify their environment and burn carbon, practices that now have us in the throes of climate change. Fire is even tied to the rise of patriarchy — by allowing men to go out hunting while women stayed behind to cook by the fire, it spawned gender norms that still exist today…
