Lice: Dedicated Followers of Fashion

Not all palaeopathology is about death, believe it or not, and sometimes researching the diseases of the past can actually tell you a lot about how people lived. Sometimes this insight can take a surprising form and one excellent example of this is the origin of clothing.

Clothing is a quintessential human technology. Palaeontologists speculate that Neanderthals may have used clothing but generally it is truly one thing that sets us apart. Being hairless ourselves clothes were a very necessary innovation in our journey to conquer the globe and understandably this element of our evolution has attracted a lot of interest and speculation. The problem is that there is very limited archaeological evidence of when our ancestors first began weaving cloth or sewing leather. In general clothing doesn’t preserve very well and usually rots away fairly soon after burial. There have been a few telling discoveries though, such as bone and ivory needles from 30,000 year old deposits in Russia, or wild flax strands of roughly the same age from Georgia. Generally though remains are scarce and it was thought that this might be one question that would never be satisfactorily answered. Then new evidence emerged from a rather surprising source.

Body_lice
Body Louse. Source: Wikimedia Commons

When most people think of lice they probably immediately think of the head lice that almost every child catches at some point. Or perhaps of the lice of more intimate areas which can cause a great deal of itching and embarrassment. But this overlooks the third lice species which relies on humanity for its livelihood; the humble body louse. They’re small (around 2-3 milimetres), flat, dark brown and are closely related to head lice. The really interesting thing about them though is that instead of living in our hair they live in our clothes. They are highly specialised, having split off in the distant past from their head-living relatives, and have been making their way by infecting our cuffs and seams ever since. This means that if we can work out when in evolutionary history body lice parted ways from head lice we could calculate when humans started wearing clothes.

Since we know that head lice and body lice are related (pubic lice are more distant cousins, probably relatives of gorilla lice) the first step is to sequence the genomes of both. By comparing the number of differences it is possible to work out how long ago the populations diverged. One such study was carried out in 2003 by sequencing the mitochondrial DNA of 40 head and body lice. The results suggested that the two groups had first split around 72,000 years ago. Then in 2011 another study carried out a similar investigation and put the figure at closer to 83,000-170,000 years ago. That puts it at the time when our ancestors were still living in Africa but after the evolution of so-called Anatomically Modern Humans (AMH), which basically means people indistinguishable from us. This is fascinating because it suggests that other hominid species, like the earlier Homo erectus, and Neanderthals themselves, didn’t utilise clothing. If true this means that clothing is a truly human invention.

The moral of the story is that there is always another way to look at a problem. Parasites which have lived intimately alongside us for thousands of years can help shine a spotlight on obscure parts of our own evolution. It is important to note, however, that this doesn’t absolutely discount the possibility of Neanderthals wearing and using clothes, but it does suggest that they evolved the technology totally independently of humanity.

Reference: Toups, M.A., et al. 2011. The Origin of Clothing Lice Indicates Early Clothing Use by Anatomically Modern Humans in Africa. Molecular Biology and Evolution. 28(1). 29-32. doi: 10.1093/molbev/msq234

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