Getting injuries from burns played a central role in the rapid evolution of humans, according to a new study.
Scientists at Imperial College London argue that humans’ close relationship with fire meant our ancestors were far more likely than other animals to suffer burns – and survive them. Over time, this exposure may have shaped how our bodies heal wounds and fight infection, leaving a lasting mark on our DNA.
“What makes this theory of burn selection so exciting to an evolutionary biologist is that it presents a new form of natural selection – one, moreover, that depends on culture,” said paper author and evolutionary biologist Prof Armand Leroi from Imperial’s department of life sciences.
“It is part of the story of what makes us human, and a part that we really did not have any inkling of before.”
While minor burns usually heal quickly, larger or deeper burns that take longer to heal can introduce bacteria to the body, increasing the chances of infection.
The researchers think this drove key genetic adaptations, with evolution favouring traits that helped humans survive burns. For example, faster inflammation and wound closure, as well as stronger pain signals.
Published in journal BioEssays, the study compared the genomic data of humans to other primates. The researchers discovered that the genes associated with burn and wound response showed signs of accelerated evolution in humans, in the form of increased mutations in those genes. These changes likely gave human skin a thicker dermal layer, more deeply positioned hair follicles and sweat glands.
Yet this likely involved a trade-off, the paper argues. Adaptations like increased inflammation are better suited to healing small to moderate burns, and can actually cause more harm in the case of larger ones.
This could explain why severe burns can lead to extreme inflammation, scarring and, sometimes, organ failure.
The researchers think that the discovery could help to explain why some patients heal well or poorly after a burn, and improve treatment for burns and scars.
“This is an area that is highly under-explored and presents an area of new enquiry for understanding responses to burn injury,” Prince Kyei Baffour, burn specialist and lecturer at Leeds Beckett University, who was not involved in the study, told BBC Science Focus.
Baffour suggests that further exploration may focus on other forms of fire exposure, such as exposure to smoke.
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