Tuesday, May 01, 2007

Toxoplasma gondii's South American origins and its influence on culture   posted by agnostic @ 5/01/2007 11:03:00 PM

Would there have been a Goya without the Columbian Exchange?

It would require many volumes to catalogue the ways in which human gene flow from Iberia and Africa into South and Central America has affected the history of the New World, while at first blush the matter of human gene flow from the Americas into Iberia and Africa might merit little more than a book or two. However, humans are not the only living things whose genes might flow in one direction or another. A simple example is corn, which when introduced into Spain became a popular staple among peasants -- so much so that many were plagued by an epidemic of pellagra for relying solely on corn, which lacks niacin. But is it possible that gene flow of another sort might have affected European high culture? After all, when we think of the culture of Spain, we typically think of The Golden Age writers, Goya, Gaudi, Segovia -- not outbreaks of pellagra.

A short and freely available article
from last year in PNAS argues pretty persuasively that the pathogen Toxoplasma gondii, which has already been shown to affect human personality and culture, originated in pre-Columbian South America. The reasoning is simple: it is much more polymorphic at neutral sites within South America, and shows a striking lack of diversity elsewhere. The less diverse forms elsewhere likely reflect smaller founder populations that were carried away on European ships. (The same reasoning suggests that Africa is the ancestral homeland of human beings.) As the Europeans returned from their initial voyages to South America, they probably brought back with them infected cats and rats, as well as soil contaminated by cat feces. Because Iberia was an agricultural society with greater population density than pre-Columbian South America, T. gondii likely found much more ideal conditions for increasing its virulence, not to mention that European populations were innocent of its existence and so likely had no defenses. The authors argue that, from there, maritime travel spread the pathogen to the rest of the world.

As Razib mentioned in his review of the study that showed T. gondii's effect on human personality, the germ has somewhat different effects on men vs women. Since we're considering high culture, we need only concern ourselves with its effect on males. The short and skinny is that it raises levels of novelty-seeking and Neuroticism, a trait that measures how easy it is for a person to become emotionally worked up. One study by Cattell found that eminent researchers he interviewed tended to be more emotionally stable. For artists, though, you don't really need me to tell you that they tend to be emotionally excitable. Novelty-seeking is obviously important for both domains.

To return to the theme of genius germs, artists show a stronger bias toward being born during the Winter and Spring than scientists, which is consistent with the hypothesis that an early infection (more likely during the "flu season") starts the individual's personality off on a more Neurotic groove. So perhaps the flourishing of T. gondii among a virgin European population contributed to the explosion of artistic creativity that we see starting about the 17th Century. Greg Clark's new book, A Farewell to Alms, argues that the Industrial Revolution could not have happened far earlier than it did, in part because the English were simply not genetically prepared for it -- they were predisposed to abandon rather than conscientiousness. Maybe the same is true for artistic revolutions -- a population may have to wait for an outbreak of nuttiness in order to produce a Beethoven or a Goya. As the population adapts defenses against pathogens that affect personality, and as sanitary conditions improve, the frequency of bona fide weirdos diminishes, and what remains are faux iconoclasts like we see in Modern Art. Andy Warhol is a good example: his eccentricity was probably little more than an affectation.

The case of Western Classical music is particularly instructive, and anyone's theory of what produces artistic genius has to contend with this medium and time-frame. Unlike all other art forms, there is almost nothing of impressive value from "Ancient music" or even most Medieval music. There is a hint of sophisticated music during the Renaissance, and then suddenly there is an explosion during the Baroque, Classical, and Romantic eras -- after which there is a figure here or there who you might compare to a "mediocre" Baroque composer, but none you would comfortably rank alongside Bach. The early great works of the Baroque begin about the 1720s, and by the mid-1800s most of the rest of the Greats were dead; Wagner died toward the end of the 19th C., and most of the leading candidates for "Great 20th Century compositions" debuted before 1920. How can the near entirety of an artistic domain have been created within scarcely 200 years, burning out as abruptly as it caught fire?

I initially thought an epidemic of some infectious disease was likely, since there were plenty of outbreaks of cholera, typhoid, and others back then. Syphillis, maybe? That seems plausible at first, but that disease really does appear to make you quite nuts. If it were something less severe, but that still affected the brain and personality, it could have been the newly introduced T. gondii germ, which would have taken some time to reach Germany and France. England actually has quite low levels, despite Britons' reputation as cat-lovers, and they have never produced a composer on the level of any Continental -- and not because there was no demand for or encouragement of such music. When Haydn arrived in London, he was overwhelmed by how greatly he and other Continental composers were worshipped in England. The only composer of high eminence who can claim to be an Englishman was in fact a German import: Handel. The Scandinavian countries likewise were not principal actors during the great period of classical music; the population there is more spread out, and the climate is much colder, so T. gondii might have had a harder time causing epidemics there (current levels are also very low there). Iberia and Italy would have been struck early since they have more hospitable climates and have many ports that would have welcomed ships returning from the New World.

Surely there are many necessary conditions for artistic genius to flourish, and to reiterate the point of another post on extreme deviations, if one component is lacking, the entire edifice collapses. Before and after the great period of Western music, all of the other components may well have been in place, waiting for an outbreak of oddballness. These days, no one would allow a purposeful epidemic in the hopes that it might produce one Beethoven among the millions of other lives it would ruin, so we may have to just wait for something similar to happen naturally and hope that some good comes of it. Until then, if my conjecture is on the right track, those who treasure Western high culture may owe a debt of gratitude to an obscure South American parasite that we contract via infected cat shit.

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