![]() ![]() Rushing to the source of the noise, the man found that a baboon had broken his chain and grabbed a little girl. One day while working in his office, the trainer heard a little girl scream. ![]() Man with Sharp Stick (1891)Ī superintendent and monkey trainer at the Woodward Gardens in San Francisco relayed the story of a fight he’d had with a primate to the San Francisco Chronicle in 1891. *(The methods note that they used a Gillette Mach 4 to shave the arms – scientists are delightfully meticulous in their note-keeping).Chimpanzee Results: Easy victory for what was probably a chimpanzee.Ĭase Study #2: Baboon v. Human fine body hair enhances ectoparasite detection. These ideas could co-exist quite happily with the notion that the need to avoid the bites of parasites helped to drive the evolution of the semi-naked ape. He also suggested that hairlessness might have made our ancestors more sexually attractive to each other. Darwin suggested that hairy humans would have risked overheating in the open African savannah, and naked skin cools more easily through sweating. Obviously, this is far from the only reason why humans might have lost our thick body hair. There’s an optimal length of fuzz where parasites are easiest to spot, and we might have hit upon it. This study provides a nice explanation.”ĭean and Siva-Jothy suggest that hair loss did help to reduce the risk of parasites, but that total loss would have made things worse. “I have often wondered why we still have fine body hair on our legs and arms. “The paper really made my day when I read it,” he says. By using the same volunteer in both conditions, the authors controlled for individual differences that might affect the results.” Markus Rantala, a parasite specialist from the University of Turku in Finland, has argued for the same hypothesis. Pagel says, “This new paper supports our idea that we lost our coarse hair because it provides a refuge for ectoparasites. (It may not be a coincidence that humans are the only species of primate to suffer from fleas.) We adapted by losing our thick hair – our finer fuzz not only harbours fewer parasites, but makes any stragglers easier to find. Early humans probably lived in large groups within a fixed base, which would have made perfect staging posts for parasites to breed and spread. In 2003, Pagel and Walter Bodmer promoted a century-old hypothesis in a paper simply titled: “ A naked ape has fewer parasites”. “This is a welcome paper,” says Mark Pagel, who studies human evolution at the University of Reading. These results show that vellus hair makes it easier for people to feel the footfalls of parasites on their skin, while also making it harder for the parasites to start feasting. And the hairier they were, the better they were at detecting the bugs. They had to use a clicker every time they felt something crawling about, and they did so twice as often for their unshaved arms than their naked ones. The students also found felt the bugs more quickly when the hairs were around. Without the hair, they searched for just 18-19 seconds. With vellus hair, the bedbugs took between 22 and 26 seconds to find a good place. They had to intervene quicker if the arms were shaved. They waited until the bug started to extend its bloodsucking snout before plucking it off. While the volunteers looked away, Dean and Siva-Jothy placed a bedbug within the rectangles. ![]() The duo recruited 29 student volunteers and drew a rectangle of Vaseline on both their forearms, after first shaving one of them. Some have suggested that they have no role at all.īut Isabelle Dean and Michael Siva-Jothy from the University of Sheffield have an intriguing possible answer: they think that the vellus hairs help us to spot parasites. They look like the results of a half-hearted evolutionary stab at becoming hairless. But very few of them have offered answers to an equally mysterious question: why have we kept our vellus coat? The fine hairs aren’t very good at preserving body heat, and they don’t make us more or less sexually attractive. Many scientists have speculated about why we humans have lost a thick coat of body hair. We are coated with a layer of short, fine hair, known technically as vellus hair and colloquially as peach fuzz. We actually have the same density of body hair as other apes of our size, but ours is largely fine and colourless rather than thick and dark. It might seem like a deserved nickname after all, we lack the lush coats of body hair that chimps, bonobos and gorillas have in abundance. We humans are often known as “ naked apes”.
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