Peer-reviewed / Observational study / People
Exposure to burn injuries played key role in shaping human evolution, study suggests
Humans' exposure to high temperature burn injuries may have played an important role in our evolutionary development, shaping how our bodies heal, fight infection, and sometimes fail under extreme injury, according to new research.
For more than one million years, the control of fire has powered human success, from cooking and heating to technology and industry, driving genetic and cultural evolution and setting us apart from all other species. But this relationship has also exposed humans to high temperature injuries at a scale unmatched in the natural world.
Humans burn themselves – and survive burns – with a frequency likely much greater than any other animal. Most animals avoid fire completely, while in contrast, humans live alongside fire and most humans will experience minor burns throughout their lives.
A new study published in BioEssays, led by Imperial College London researchers, suggests that this increased exposure to burn injuries may have driven notable genetic adaptations which differentiated humans from other primates and mammals. This may also explain both beneficial and maladaptive responses to severe burn injury.
Burn injuries exist on a spectrum of severity, with most small injuries healing on their own while severe burns can lead to lifelong disability or death. Burns damage the skin, the body's main protective barrier against infection, sometimes over large areas of the body. The longer the skin is damaged, the greater the risk that bacteria can enter the body and cause overwhelming infection.
The researchers argue that natural selection would have favoured traits that helped humans survive small to moderate burns. These may include faster inflammation, faster wound closure (to prevent infection) and stronger pain signals.
However, while these traits are helpful for less severe injuries, they can become harmful for large burns, which may explain why modern humans can experience extreme inflammation, scarring, and organ failure from major burns.
Using comparative genomic data across primates, the researchers found examples of genes associated with burn injury responses which show signs of accelerated evolution in humans. These genes are involved in wound closure, inflammation and immune system response – likely helping to rapidly close wounds and fight infection; a major complication after burn injury, particularly before the widespread use of antibiotics.
These findings support the theory that exposure to burn injuries may have been a notable force on the evolution of humans.
Dr Joshua Cuddihy, lead author for the study, and Honorary Clinical Lecturer in Imperial's Department of Surgery and Cancer, said: "Burns are a uniquely human injury. No other species lives alongside high temperatures and the regular risk of burning in the way humans do.
"The control of fire is deeply embedded in human life — from a preference for hot food and boiled liquids to the technologies that shape the modern world. As a result, unlike any other species, most humans will burn themselves repeatedly over their lifetime, a pattern that likely extends back over a million years to our earliest use of fire.
"Our research suggests that natural selection favoured traits that improved survival after smaller, more frequent burn injuries. However, those same adaptations may have come with evolutionary trade-offs, helping to explain why humans remain particularly vulnerable to the complications of severe burns."
The research was developed through a collaboration between burn injury experts, evolutionary biologists, and genetics experts at Imperial, Chelsea and Westminster Hospital NHS Foundation Trust, and Queen Mary University of London.
The study's novel perspective on human evolution, which could reshape our understanding of modern burn care and human biology, was made possible through interdisciplinary collaboration between clinicians and researchers.
Professor Armand Leroi, Professor of Evolutionary Developmental Biology in Imperial's Department of Life Sciences, said: "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. It is part of the story of what makes us human, and a part that we really did not have any inkling of before."
Yuemin Li, PhD student at Queen Mary University of London, said: "Our study provides compelling evidence that humans have unique adaptive mutations in several key genes associated with burn injury response.
"These findings could allow us to explore in future research how genetic variations in different groups impact burn injury response, potentially explaining why some patients heal well or poorly after a burn."
Unlike other wounds from cuts or bites which would have also led to infections, the increased lifetime risk of burns experienced by humans and their hominin ancestors is unique as they are the only species to regularly experience burn injuries and survive them.
The researchers' findings could change how we study burn injuries, design treatments, and interpret complications of burns. It may also explain why translating results on burn injuries from animal models to humans is often ineffective.
Declan Collins, Consultant in Plastic and Reconstructive Surgery at Chelsea and Westminster Hospital NHS Foundation Trust, said: "Understanding the evolutionary drivers that cause genetic change is an important step in burn research that will influence the way in which we look at scar formation and wound healing.
"The genetic basis for scarring variation in humans and response to tissue injury is still poorly understood, and this work will provide new angles for future research."
'Burn Selection: How Fire Injury Shaped Human Evolution' by Joshua Cuddihy et al. is published in Bioessays.
