Wednesday, November 9, 2011

An Evolved Defence Mechanism - Hair

Evolutionary psychiatrist Randolph Nesse explains one of the most basic advances in biology during the past twenty years is the clear recognition that two kinds of explanation are needed for all biological traits: (a) a proximate explanation of how the trait works, and (b) an evolutionary explanation of what the trait is for. He explains that an evolutionary perspective provides a clear focus on the function of a particular trait.

I first came to the idea of adopting an evolutionary perspective when writing the first chapter in my originally conceived how-to book on Jan de Jong Jujutsu. It was titled 'What is Jujutsu?'. Jujutsu is often described in terms of the generic nature of the term, techniques, history, and the application of the philosophical concept of ju. When attempting to compare jujutsu to other martial arts, I started to come to an evolutionary explanation. Why is jujutsu different from karate, kung fu, pencak silat, boxing, etc? It's because of its evolutionary past; the evolutionary forces which shaped these different martial arts. I remember now, I was nudged in this direction by the work of Karl Friday in Legacies of the Sword.
To be sure, all such 'martial arts,' as forms of single combat, share some commonality of function - but then, so do Chinese tai chi chuan and US Air Force fighter tactics. They also, as arts developed in neighboring countries through which individuals - and armies - regularly traveled back and forth, show some degree of cross influence and even some common vocabulary. But the historical circumstances under which these various arts evolved, the purposes they served, and the statuses they assumed in their respective cultures diverged in fundamental ways. (p6)
The first kyu grading in the Jan de Jong jujutsu grading system includes an oral explanation of the history of jujutsu. The first dan grading includes a written essay on the history of jujutsu. The history does not necessarily tell why jujutsu is what it is. An evolutionary explanation does. I'll be changing these gradings to an evolutionary explanation rather than a historical explanation, as an evolutionary perspective has a clear focus on function.

I came across this paper this morning: 'What can animal aggression research tell us about human aggression?' by Blanchard and Blanchard in Hormones and Behavior 44 (2003) 171–177. They made the following comment which specifically refers to martial arts training:
Although factors such as weapons and specific training in martial arts undoubtedly alter the response characteristics of aggression in people, there are some hints that human physical attack may be more similar to the aggression of nonhuman animals than might be thought, for example, target sites for attack.
They go to explain that in some mammalian species, structural adaptations have evolved to defend vulnerable targets for attack.
Thus in lions, the only group-living large cats, males (only) have developed a thick mane that covers from the top of the head to the shoulders, potentially affording protection for this site during fights among males within social groups, as well as protection for the group and its young from nomadic males. The late Margaret Manning,a distinguished child psychologist working primarily with young children, suggested that in these children, the head is the primary target for offensive attack (personal communication). In this regard, two seeming anomalies of human physiology are of interest: first, human head hair is unique in growing indefinitely, potentially (and especially if unwashed, as it likely was during most of human prehistory) providing a thick mat offering a great deal of resistance to blows. Second, humans, like lions, have a gender-specific locus for particularly coarse and wiry hair; in humans, the lower face. Moreover, beards appear at precisely the developmental time period when male–male aggression becomes particularly dangerous, due to the enhanced strength that accompanies adolescence and the additional motivation associated with fights over access to females. While beards are often taken to have evolved as signals of sexual maturity, it is not clear why yet another addition to the many behavioral as well as structural signals of maturity in males would be necessary or adaptive. Similarly, if beards have evolved on the basis that they elicit sexual interest in females, one might expect at least some indication of this interest in contemporary women. However, a recent survey of 80 undergraduate women from a number of different cultural backgrounds indicated little (in fact a slight net negative)sexual response to male beards.
Now I'm conflicted over shaving off my beard. Evolution is about increasing the chances of survival and reproduction. It would appear the two evolutionary imperatives are at odds in this case. Increase my chances of surviving an offensive attack by a cospecific, or increase my chances of reproduction with a cospecific. What to do, what to do. ... I'm male, so it's pretty obvious which imperative is going to win out.

Just something of interest concerning our evolved defence mechanism.

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