What I Wish I Knew Then About Lice By Rebecca Isaac

I remember the first, last, and only time I was told that I had lice (Pediculus humanus capitis). I was in the 2^nd grade and my head had been itching so much, and deep down in my 9 year old self I knew that I had lice. Kids can be so mean, and even after I had endured the terrible Nix lice head comb, the burning Nix head shampoo treatment, and my parents and I had washed EVERYTHING in the house (including furniture) with scalding hot water—kids taunted me for weeks. Little did we all know that those lice were more than just microscopic, ectoparasitic members of the Phthiraptera order; through evolutionary study we could actually help tell the story of the evolution and migration of the human race. So yes, there was some slight discomfort when my 9 year old long hair and scalp were shoved under the scalding hot faucet, but there should also be molecular evolution papers in Nature being written about those special inhabitants I had. They not only linked me to my ancestors, but my ancestors from 100,000 years ago, it turns out (Kittler, et al. 2003).

Figure 1 (Kitler, et al. 2003)

According to an article published by Current Biology, scientists studied the mtDNA and nuclear DNA segments from human head and body lice from all different parts of the world in order to determine if the evolution of body lice transpired from the migration of humans out of Africa (Kittler, et al. 2003). In other words, scientists were curious to see if the evolutionary traits of lice matched with the evolutionary history of their human hosts dating back to their time in Africa and perhaps even before.  Their materials and methods included “a global sample of 40 head and body lice” and using a chimpanzee louse for the outgroup (Kittler, et al. 2003). They used statistical analysis such as Tajima’s D as well as compared the known mtDNA sequence data and used Poisson amino acid data for dating the nodes of the generated and linearized mtDNA tree (Kittler, et al. 2003).  Based on the generated phylogenetic tree shown, these scientists believed that what the molecular evolutionary data of these lice supports the evolutionary data found amongst humans. Lice, just like their human hosts, originated in Africa. Additionally, the molecular evolutionary data supported the widely accepted scientific belief that body lice evolved from head lice and that this finding corresponds with the development of the earliest known forms of human clothing, which falls within the reasonable estimation of 72,000±32,000 years. The earliest known gadgets being used to create clothing are roughly 40,000 years (Kittler et al., 2003).  

Thus, it seems that the molecular evolutionary data suggests that lice developed, and were closely influenced, by the changing cultural and migratory patterns of our ancestors from Africa. With a little bit of patient analysis and persistent evolutionary observation, all of that corroborating evidence was found, and supported, by something smaller than the already microscopic Pediculus humanus capitalis—mitochondrial and nuclear DNA. Had my 9-year old self been able to understand that, maybe that brief moment of stress in my childhood would have seemed a little cooler then….or maybe not. The point is, despite the fact that lice are vectors for infectious diseases such as epidemic typhus fever, epidemic relapsing fever, and trench fever, which are terrible for sure; however, they also carry a whole lot of human evolutionary information that can be valuable if we can manage to look a little deeper past the nuisance and into the significance of what these, and other pests, can share with us about our own evolution and history.

Word Count: 610

Citation: Kittler, Ralf, Manfred Kayser, and Mark Stoneking. "Molecular Evolution of  Pediculum humanus and the Origin of Clothing." Current Biology. 13. (2003): 1414-1417. Print.