community and immunity

Carl Zimmer's latest article for Discover probes the intriguing possibility that some social behaviors are the result of evolving immunity. A sample:

Another prediction of the behavioral immune system hypothesis is that we are more vigilant against getting sick when we are more vulnerable to disease. Carlos Navarrete, a psychologist at Michigan State University, and his colleagues looked into this issue by studying pregnant women. Infections are especially dangerous during the first trimester. When a woman first gets pregnant, her immune system is suppressed so it does not accidentally attack the fetus. In later months the immune system returns to normal and the fetus develops an immune system of its own.

Navarrete and his colleagues had 206 pregnant women read two essays that were written, they were told, by students. One of the essays was by a foreigner who criticized the United States, the other by an American who praised the country. The women then had to rate the essayists for their likability, intelligence, and other qualities. Women in the first trimester were more likely than those in the second or third trimester to give a high score to the American and a low score to the foreigner. The pregnant women’s vulnerability to infection, Navar­rete concludes, brought with it a heightened disapproval of foreigners.

Results of preliminary investigations are far from conclusive. Still, it's fascinating to think that the roots of sociality might partly lie in the body's eternal war against pathogens.