If that scab on your elbow is still lingering weeks later, you’re not imagining things—your body is just really slow at healing.
According to a new study published in Proceedings of the Royal Society B, humans take up to three times longer to heal wounds than our closest primate relatives. And the reason might be tied to a strange evolutionary trade-off: we ditched fur for sweat glands.
Researchers examined healing rates in humans, chimpanzees, and several Old World monkey species, along with rats and mice. While rodents and monkeys all healed at roughly the same pace, humans lagged far behind. The findings suggest that slow healing isn’t a universal primate trait—it’s something uniquely human.
“Human wound-healing rates were found to be markedly slower,” the researchers noted. “Approximately three times slower than those observed in non-human primates.”
Why Human Wounds Heal 3 Times Slower Than Other Mammals
To get these results, scientists looked at both lab-created wounds in animals and post-surgical wounds in 24 human volunteers recovering from skin tumor removals. In chimps, they relied on photographs of naturally occurring injuries taken over several days or weeks. Despite the differences in how injuries were tracked, the outcome was consistent: humans are terrible at healing.
So what gives? One theory is that our lack of fur made us more vulnerable to injury, prompting evolution to thicken our skin for protection. But thicker skin may come with slower tissue repair. Another idea is that sweating, a cooling system that relies on a dense network of glands, makes skin more prone to damage, which could also delay recovery.
The timing of this adaptation is telling. Humans diverged from chimpanzees around six million years ago, so our sluggish healing likely evolved sometime after that split. Other primates still covered in fur seem to have maintained the original, faster healing rate.
While healing slowly might seem like a bad evolutionary move—it takes more energy and could increase vulnerability—the researchers suggest that early human societies may have offset this disadvantage. Social care, herbal remedies, and cooperative living might have bought us the time we needed to heal.
Still, the reason behind our delayed healing remains an open question. The study’s authors are calling for a broader approach, combining fossil evidence, modern genetics, and primate biology to fully understand what changed—and why.
In the meantime, if your scrape won’t go away, don’t blame your immune system. Blame evolution. We may have traded in quick recovery for the ability to cool down. Whether that was worth it? Jury’s still out.
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