Tuesday, March 12, 2013

More lice on the naked ape

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)
Books that bring human biology out of the covers usually sell well and although most of us would have read the works of Desmond Morris, it is not often that one actually examines the depth of research in popular writing. A bit of browsing led me to a rather remarkable book by Lawrence Langner called The importance of wearing clothes (1959) which is out-of-print (a digital version can be found on the Internet Archive) and what surprised me more was that it finds mention neither in the Naked Ape nor in Peoplewatching. More remarkable is that Langner, as is evident, was a deep thinker, an excellent researcher but mostly known for being a playwright and seems to have moonlighted as a patent lawyer. An excellent writer, a friend of John Steinbeck (the book is a follow up on a play "Lady Godiva" and dedicated to him) and George Bernard Shaw among other freethinkers, he questions what most laypersons take for granted about human clothing and notes the bias in the western view of cultures at his time where nudity was not acceptable as a norm unlike in some hunter-gatherer societies.

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
Playwrights are thinkers who excel in the art of putting themselves in the shoes (or out of them in this case) of others. Some years ago I read an excellent essay on why actors would make excellent software designers for exactly the same reason - they can put themselves in the shoes of others and judge software as if they were persons. (It is not surprising that books on user interface design like About Face by Alan Cooper are well received. I have more to say on this topic, particularly on the personality traits that one could attribute to Indian government websites which shine as hall-of-shame  examples that demonstrate a lack of empathy for potential users and portray the worst of government administration. That post will however have to wait for another day.) Langner, the playwright appears to have begun considering the question of human clothing and nudity after writing a play on the subject "Lady Godiva". Langer considers the "why wear clothes" question in his first chapter and suggests protection of the body (especially of men) so as to allow movement through grass and jungle as a driving force in the warmer regions and the more obvious protection from cold in higher latitudes. He attempts to put an evolutionary structure to clothing - starting with primitive aprons for men going on to animal hides and to the use of stitching. He suggests ornaments as precursors of female clothing. In subsequent chapters he branches off into other cultural and social aspects of clothing. Langner quotes extensively from the writings of M.D.C. Crawford (Philosophy in clothing) and J. Flugel (Psychology of clothing - a title reused by Dearborn in 1918) uses many interesting notes and illustrations. Perhaps it is the lack of biological reasoning that leads to the paucity of citations to Langner's work. Or perhaps it is contempt for easy to read research by and for non-professionals, which is reminescent of the contemporary reception to works like The Origin of Birds (by Gerhard Heilmann). Langner ultimately comes to the odd conclusion that clothing brings us closer to our conception of divinity.

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 flea
Has smaller fleas that on him prey;
And these have smaller still to bite ’em;
And so proceed ad infinitum.      -Jonathan Swift

One 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)

* 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)
Further reading

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