That’s what two scientists from University of New Mexico are claiming in a recently published study. The gist is that people seem to do better against infectious diseases when they are fractured and isolated into various societies and sects. Thus, we would expect to see a far greater diversity of religious sects in tropical areas with many dangerous infectious diseases. And, apparently, we do.
“Why does Cote d’Ivoire have 76 religions while Norway has 13, and why does Brazil have 159 religions while Canada has 15 even though in both comparisons the countries are similar in size?” they ask.
The reason is that religion helps to divide people and reduce the spread of diseases, which are more common the hotter the country, the research suggests.
Any society that increased its coherence by adopting a religion, and dealt less with local groups with other beliefs as a result of cultural isolation, gained an advantage in being less likely to pick up diseases from its neighbors, and in the longer term to have a slightly different genetic makeup that may offer protective effects, for instance by making them less susceptible to a virus.
Unless there’s more to it, this strikes me as a remarkably weak argument. I can think of a heck of a lot of other factors that set tropical areas apart from, say, Norway, in ways that seem much more relevant to the development of religious sects. Poverty is a huge one. Lack of education. Lack of, well, health care to deal with the misery of disease. Maybe the researchers have controlled for all these other, more plausible effects, but I don’t see any discussion of this critical methodological challenge in the article.
And, of course, there’s always the alternative model of causation: it’s religious differences that cause disease, as the one-true God smites those who try to get too creative in their worship!
Off topic, but can anyone explain what the final sentence of the article means? Is it just a editing oversight? Because it doesn’t seem to make much sense:
In earlier work, the team linked the rise in the numbers of women who worked with left wing and liberal politics.
The Bad Idea Blog 
The link was between “left wing and liberal politics” and “the rise in the numbers of women who worked.”
Man, I knew I was too low on sleep. I just couldn’t read it any other way than “women working with left wing and and liberal politics” as it it were all one phrase.
To be fair, it *is* poorly worded; it probably should have been something like:
“In earlier work, the team linked an increase in left wing and liberal politics with an increase in the numbers of working women.”
:-D
As soon as I saw the work was from UMN, I thought “I bet that was Thornhill’s pile of crap!”
That guy is one of the worst sociobiologists ever.
He has made an entire career out of “just so’ stories–including many papers on the “adaptive” benefits of rape.
I just read another, similar article by these guys (“A parasite-driven wedge: infectious diseases may explain language and other biodiversity”, Oikos 117: 1289-1297, 2008). Then I looked on the web if anyone else thought this is rubbish. I can’t comment on the Proc Roy Soc article but I have a feeling it’s a very similar story with ‘religion’ instead of ‘language’.
I’m all for integration of biology and anthropology – and may the truth be heard, politically incorrect or not (rape, religion, whatever). I got an indigestion from the anti-scientific stance prevalent when I was a social science undergrad.
All the more reason to be angry at, as Bug Girl says, poor ‘just so’ stories. And Fincher and Thornhill (in Oikos) really just posit the “pathogen diversity -> cultural/species [not the same thing!?] diversity” theory without any sound argument. They even mention the opposite causal chain, quoting Krasnov (“diversification of parasites is a response to diversification of hosts”). To me this seems at least as if not more plausible, since there are a whole lot of reasons for which hosts would diversify, genetically and still more so in the fast-change zone of culture and politics. But then they sort of say ‘BUT that is not what we say’ and argue that “the dominant (sic!) mode of speciation and population/culture divergence in high parasitic stress regions (low latitudes) has been parasite-driven”. All without any more argument than some sloppy abracadabra with partial correlations that really give no clue about causality at all.
I could go on but enough time wasted on this nonsense.
For more arguments against their story read DSKS’s post at the link below.
Bleh.
http://scienceblogs.com/evolvingthoughts/2008/08/the_heat_of_religion.php
I’ll just add that I don’t think the causal effect they propose seems impossible. They just don’t substantiate it at all, and it hardly seems necessarily ‘dominant’.