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Mastering fire may have also led to genetic changes that helped early humans survive mild burn injuries, but this evolutionary trait could complicate the treatment of more severe cases today.

An suggests that the selection of genes preventing deadly infections that could arise from minor burns were prioritised in early Homo sapiens, but these same genes interfere with the healing of severe ones. This may be because, in primitive times, people with severe burns had almost no hope of surviving.

For at least 1 million years, hominins have been using fire – whether for cooking, warmth, protection or tool manufacture – and so putting themselves at risk of burns. Scientists have already found that Homo sapiens may have evolved to overcome some kinds of smoke toxicity.

at Chelsea and Westminster Hospital NHS Foundation Trust in London and his colleagues suspected that fire-related skin injuries might have shaped human evolution too. To find out, they analysed previously published data on the genes expressed in burnt and healthy skin of rats and humans, identifying 94 that were only expressed during burn healing.

They then ran further analyses on published genetic data from humans and chimpanzees, our closest living relatives. The team looked for signs of enhanced natural selection for these 94 genes in humans compared with chimpanzees, pinpointing 10 burn-healing genes that underwent significantly stronger selection in people.

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Three particularly highly selected genes – that promote pain sensation, scar tissue formation, inflammation and wound closure – probably would have helped rapidly close smaller burns to ward off infections and promote inflammation to fight any potential pathogen, according to the team’s results reported at the American Burn Association’s annual meeting in Phoenix, Arizona, this month.

But inflammation and scar tissue can complicate the healing of larger burns, so the same genes that promote the healing of minor burns seem to hinder the healing of major ones. This could complicate treatments today, when physicians have the tools to help people with such injuries.

“This is a very significant result, as it testifies to the unique, culturally driven co-evolutionary dynamics characterising human evolution,” says at Tel Aviv University in Israel.

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at the University of Oxford calls the idea “novel and intriguing” and the results “promising and biologically plausible”. Even so, validating the hypothesis would require significantly more research with a larger variety of primate species, including extinct hominins, he says.

at Millennium Nucleus on Early Evolutionary Transitions of Mammals in Santiago, Chile, and brother to Thomas Püschel, seconds his sibling’s assessment. “The directionality of these genetic changes in humans remains insufficiently resolved,” he says. “And the specific traits and mechanisms subjected to selection during hominin evolution are not clearly defined, leaving this otherwise intriguing hypothesis still underdeveloped and rather speculative.”