Flu blues

Will the swine flu lead to the next big evolutionary change for humans? No. But it has already begun to affect the way people interact with each other. I wandered onto campus a couple of weeks ago and saw people wearing face masks! We’ve been asked to plan for our “essential” classes in the event of a pandemic.

It’s a good time to be on leave. But my kids’ school has been closed the rest of the week. It’s the flu – more than a third of the whole school was out sick yesterday.

In the August Smithsonian magazine, writer Rob Dunn discussed a hypothesis that tries to relate cultural diversity and xenophobia (fear of the other) to the rate of infectious disease (“The culture of being rude”):

In a series of high-profile papers, Corey Fincher and Randy Thornhill, both at the University of New Mexico, and Mark Schaller and Damian Murray of the University of British Columbia argue that one factor, disease, ultimately determines much of who we are and how we behave.
Their theory is simple. Where diseases are common, individuals are mean to strangers. Strangers may carry new diseases and so one would do best to avoid them. When people avoid strangersthose outside the tribecommunication among tribes breaks down. That breakdown allows peoples, through time, to become more different.
Differences accumulate until in places with more diseases, for example Nigeria or Brazil, there are more cultures and languages. Sweden, for example, has few diseases and only 15 languages; Ghana, which is a similar size, has many diseases and 89 languages. Cultural diversity is, in this view, a consequence of disease.

On the surface, this seems a poor example – the population has been thin in Sweden relative to Ghana for most of the last 6000 years, until the rise of the Swedish state. It’s no surprise that a recent population expansion coupled with political centralization would result in a relatively uniform language and culture area.

But as the article goes on to explain, some of the theorists think that the rise of states is itself a dependent variable. They would propose that the growth of polities was limited in Ghana because of a high disease load, retaining and fostering a cultural diversity that would have been wiped out by natural political consolidation in a less-disease-prone region of the world.

That’s the logic, at least.

This kind of topic is interesting but endlessly frustrating. The frustration – at least for me – comes from the ready confusion of biological and cultural processes of change. Dunn’s article says as much:

As a rule, it is good to be skeptical of biologists who, like Fincher and Thornhill, propose to explain a whole bunch of things with one simple theory. More so when those biologists are dabbling in questions long reserved for cultural anthropologists, who devote their careers to documenting and understanding differences among cultures and their great richness of particulars. Biologists, and I am no exception, seem to have a willingnessor even needto see generalities in particulars. Finchers new theory would offer an example of these desires (and a little hubris) run amok, of biologists seeing the entire history of human culture through one narrow lens. It would offer such an example, if it didnt also seem, quite possibly, right.

As a rule, I’m skeptical of everything. “Wary of strangers” wouldn’t keep our school open – those kids are all catching the flu from their friends. It doesn’t take very many contacts between groups of people to spread an epidemic far and wide.

In that respect, it’s a problem for percolation theory. You’ve got a network of people through which the flu can be transmitted. If the people tend to be highly interconnected, with each other, the flu spreads widely. But even if links between groups are rare, the strong interconnections within a group can keep the epidemic alive long enough to make it to the next hop. At some critical level, the links are no longer enough, and the pathogen can’t propagate.

So does it do you personally much good to be wary of strangers, if you have a few cosmopolitan friends? Everything can make a little difference to the percolation network, but it seems to me that people carrying the “xenophobia” gene would still maintain large social networks including a few people who interacted far and wide with strangers. It’s not that the direction of the effect is wrong; it’s that a wholesale elimination of stranger contact by an individual may have little effect on her probability of infection, since friends may have gotten the pathogen from strangers.

It’s awful hard for a “xenophobia” gene to get going in that scenario.