Sunday, 9 April 2017

Ubiquitous parasites

Bill Hamilton famously was one of the first evolutionary biologists to take parasites seriously - seeing their influence everywhere. Many have subsequently followed in his footsteps. One interesting paper on the topic which I recently took in is this one:

Gregory Cochran may be known to readers of this blog because he co-authored the book The 10,000 Year Explosion: How Civilization Accelerated Human Evolution. The paper here argues that pathogens have been consistently underestimated, and we ought to be considering them more frequently in cases where fitness is adversely affected.

The paper is all about organic pathogens. However the authors appear to be ignorant of cultural evolution, and don't extend their argument to cultural pathogens. Nor is there any discussion of meme-gene coevolution. Despite this, many of the arguments they give are equally applicable to cultural evolution.

One of the examples the paper gives is human male homosexuality. Although to date, no pathogen has been discovered that causes human male homosexuality, there's circumstantial evidence that suggests that pathogens may be involved. While thinking about cultural evolution it occurred to me that there's an example of cultural pathogens causing homosexual interactions between males: the well-known case of priests and altar boys.

It's long been argued that religious memes can sterilize priests to divert resources from genes to memes and thus promote their own propagation. Dawkins (1976) gives this argument as a hypothetical example. Homosexuality could be being promoted by memes for similar reasons. Though courtship and mating do use some resources, homosexual relationships do mostly manage to skip the cost of producing children - the resources saved could go into meme propagation.

Priests seem to go for young boys (rather than young girls) about 80-90% of the time. Indeed, the church apparently seems to be an attractive institution for homosexual men and many priests are gay. However the frequency of gay priests doesn't explain the frequency with which boys are targeted. Perhaps young girls are better guarded, or maybe they are more clearly prohibited for priests in scripture. Anyway the evidence is not conclusive, but memes do appear to be promoting male homosexual behavior in this case.

Knowledge of cultural evolution is invaluable in understanding the role of pathogens on human health. Consider the obesity epidemic, for example. That's an epidemic of Candida Albicans - and other fatness-promoting gut microbes. However it is also an epidemic of food processing technology and fast-food advertising memes. The food industrial complex develops ever-evolving tasty recipes and then uses memes as targeted vectors to deliver their their fat-promoting messages to consumers. The effects of memes and genes are tangled together in this case. Without an understanding of both you don't get the full picture.

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