It's always a Bad Idea to critique a paper on the basis of summaries, but I just can't seem to make Proceedings of the Royal Society let me download this article. Randy Thornhill and Corey Fincher have proposed another explanation for religion, based on the correlation between tropics and diseases, and the variety of religions in the tropics.
Their argument, it appears, is to note that controlling for other factors you get higher numbers of religions in more tropical regions. Promoting within-group solidarity therefore is a way to prevent the spread of diseases, to prevent contagion. As The Economist summarises it:
Mr Fincher and his colleague Randy Thornhill wondered if disease might be driving important aspects of human social behaviour, too. Their hypothesis is that in places where disease is rampant, it behoves groups not to mix with one another more than is strictly necessary, in order to reduce the risk of contagion. They therefore predict that patterns of behaviour which promote group exclusivity will be stronger in disease-ridden areas. Since religious differences are certainly in that category, they specifically predict that the number of different religions in a place will vary with the disease load. Which is, as they report in the Proceedings of the Royal Society, the case.
...
The two researchers also looked at anthropological data on how much people in "traditional" (ie, non-urban) societies move around in different parts of the world. They found that in more religiously diverse (and more disease-ridden) places people move shorter distances than in healthier, religiously monotonous societies. The implication is that religious diversity causes people to keep themselves to themselves, and thus makes it harder for them to catch germs from infidels.
They make a similar argument for xenophobia.
This strikes me as a classic case of taking correlation for causation. Here's a reason why religions might be more diverse in tropical environments: Greater diversity of ecological resources permits a greater number of societies to persist. And one reason why people from "traditional" societies might move around less is because the rest of the landscape is taken up with other societies who don't take kindly to strangers moving through their territories, as any visitor to Papua New Guinea can attest.
Single-cause explanations of human behaviour are often based on the "hammer, therefore nail" principle.
Fincher, C.L., Thornhill, R. (2008). Assortative sociality, limited dispersal, infectious disease and the genesis of the global pattern of religion diversity. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1--1. DOI: 10.1098/rspb.2008.0688
Life Science
Brain & Behavior
Comments
It looks like another just-so story from the evolutionary psychology folks.
Posted by: Laelaps | August 14, 2008 10:26 AM
Well if you believe the immunologists, we prefer strangers! This is because they have different genes and hence MHCs and the mixing of MHCs is better for disease resistance. Strange thing with stories is you can make one either way.
One wonders if there are any such evolutionary type explanations made for which selective pressures can actually be measured in some currency? Retrospectively in addition?
Posted by: Natasha | August 14, 2008 10:59 AM
As Natasha said, strangers are good for small communities as they can improve genetic diversity and widen immunity. But this improvement will only apply to the survivors of any disease brought in.
Natural selection in action?
I seem to recall that this was studied in the context of lion prides. Are they religious?
Posted by: eddie | August 14, 2008 12:20 PM
I got this story from Science and Religion News (sciencereligionnews.blogspot.com) a few weeks ago, and I'll say here what I said there: that giving a biogeographical cause for religious diversity is a poor substitute for an analysis of socio-political pressures. I would also like to get a hold of the study, because I'm curious about the authors' definition of religion-- are they counting cults from northern climates, or just the larger, more organized religions? I'm willing to bet there's a lot more problems with the paper than the one big problem that we're having with the conclusion.
Posted by: DonE. | August 14, 2008 12:21 PM
move around less ... because ... [others] don't take kindly to strangers.
You didn't propose an explanation for why people in the tropics move around less, you just re-framed it as a question about why people in the tropics don't take kindly to strangers. At least the article proposes an explanation for both: to avoid the (more prevalent) tropic diseases.
-kevin
Posted by: kevin | August 14, 2008 12:22 PM
Well protecting your resources (hunting areas, plant resources, etc.) is always a good motivation. Generally large scale societies allow people to move more because the goods are traded widely. These societies also often tend to have general religions as well, again in the reverse of the proposed explanation.
Posted by: John S. Wilkins | August 14, 2008 12:29 PM
It's not just the fact that this reeks of the cum hoc ergo propter hoc fallacy, it's that the investigators are being very selective in their history of both human migration and disease epidemiology.
I'd like to hear the investigators explain the various plagues that have cut a swathe through ethnically diverse (but very much economically connected) peoples in Europe; and an explanation for the highly aggressive migration patterns of equally diverse ethnic groups, with strong religious traditions (long before even the Moors, Christians, Pagans began their conquests), into neighbouring territories all across Eurasia, Africa and, of course, Central America. Religious traditionalists are conservative in their migration patterns? Bullsh*t! Religious tradition often serves as the pretext for aggressive migration and colonisation, because it is often used to support one communities claim to resources at the expense of another. Hell, Christian missionaries were largely responsible for the initial spread of cholera all over the place, for Heaven's sake!
Posted by: DSKS | August 14, 2008 1:55 PM