I have written about lice before and some ecological studies they have inspired. There is however a remarkably simple anthropological question about why humans wear clothes and lice crop up prominently in attempts to answer that puzzle. This rather simple and perhaps ubiquitous childhood question is all too often waved away either because it is taboo or because it has the potential to embarrass. Professional researchers, particularly from less liberal countries tend to shy away from such questions. To be fair however, one must note that the question has not been resolved entirely. Biologists typically seek advantages to such behavioural traits and look for forces that might favour the selection of dressing as opposed to the lack of it.
|A newspaper article (via Google)|
|Langner, Lawrence (1963) G.B.S. and the lunatic. Atheneum, New York. p. 120|
|Rock paintings (20,000 to 12,000 year old) |
of ritual clothing from Langner's book
The puzzle of human clothing is also related to the puzzle of (relative) hairlessness. Suggestions for adaptive reasons include ideas that hairlessness may suppress ectoparasites (Pagel & Bodmer, 2003) while others have argued that it may aid thermoregulation. (Jablonski, 2004). Other bizarre ideas like aquatic origins have also be considered but the ectoparasite version gives some interesting options that can be examined using modern tools.
|12000 year old non-ritual clothing from Langner's book|
The larger ectoparasites of humans that are considered in most of these hypotheses are lice. There are three forms of them which live exclusively on Homo sapiens. Most lice actually specialized and live on very specific hosts. Theirs hosts form the islands on which they survive and the only opportunity to avoid inbreeding on their islands is to hop from one host island to another of the same species. This isolation means that their genomic edit histories can be compared to those of their host. This application is extremely well-known in birds where almost every species has its own specific bird-louse. When a bird species (mammals too) goes extinct, their specific bird-lice species can go extinct as well.* Birds can have several species on them and humans have one that favours the habitat of the hair on the head, another that favours the body and a different species that lives in the pubic region. While the head and pubic louse species hide in hair, the body loving subspecies is actually one that has to seeks shelter in clothes. Attempts to find the age of divergence of this subspecies from its nearest relative, the head louse yields an age estimate of 72,000 (with quite a lot of room for error, give or take 42,000) years. (Kittler et al., 2003) This then is a surrogate for the age of clothing.
So, naturalists observe, a fleaOne would think a better estimate might be got if the study was repeated with something that lives within the lice - an obligate endosymbiont bacterium is known (first noticed by Robert Hooke 300 years ago!) - however it turns out that at least the sequences of this bacterium that were examined were almost identical between samples from head and body lice.(Perotti et al. 2007)
Has smaller fleas that on him prey;
And these have smaller still to bite ’em;
And so proceed ad infinitum. -Jonathan Swift
* Note: there have been some suggestions that the crab / pubic louse has become endangered due to habitat loss, however there is little serious evidence for it and seems more like newspaper sensationalization.
|The crab/pubic louse and the head louse (from Lloyd, 1918)|
- ,, and (2011) Origin of Clothing Lice Indicates Early Clothing Use by Anatomically Modern Humans in Africa. Mol Biol Evol 28(1): 29-32.