TÜBINGEN, GERMANY—Whether they believe in God, evolutionary biologists may need to pay closer mind to religion. That's because religious beliefs can shape key behaviors in ways that evolutionary theory would not predict, particularly when it comes to dealing with disease, says David Hughes, an evolutionary biologist at Pennsylvania State University, University Park. In a presentation here yesterday at the 13th Congress of the European Society for Evolutionary Biology, Hughes and colleagues reported that some of today's major religions emerged at the same time as widespread infectious diseases, and they propose that the two helped shape one another. The same dynamics may be reflected today in how people in Malawi deal with the AIDS epidemic.
Although not a religious person, Hughes has long been fascinated by the power of religion to get people to behave in ways they might not have otherwise, and in particular to extend help to nonrelatives, even at a significant cost to themselves. An extreme example of this is when someone tends to the sick, risking infection and, at least in earlier times, death as a result—a behavior that doesn't make much sense from an evolutionary perspective, particularly if the sick person is not kin. For evolutionary biologists, "the question is not whether religion is correct on the issue of a God, but rather how people behave thinking there might be a God," Hughes explains.
With two Penn State colleagues, demographer Jenny Trinitapoli and Philip Jenkins, a historian of religion, Hughes read the historical literature and queried religious leaders and other experts about the world's epidemics and the way religions deal with disease. They found that between 800 B.C.E. and 200 B.C.E., cities flourished, deadly plagues arose capable of killing off up to two-thirds of a population, and several modern religions emerged. These religions all had a different take on disease, which affected how people responded to epidemics such as polio, measles, and smallpox, Hughes reported. The belief systems, for example, influenced whether people fled from disease or tried to help those who were sick.
The Christian tradition, set by the example of Jesus as a healer, stands out, Hughes says. Helping the sick was one way to ensure a trip to Heaven, so risking death from a disease's spread was encouraged. Other religions did not promote such extreme altruism. Islamic teachings basically disavowed the existence of contagious disease, despite some Arabic scholars thinking otherwise at the time. Thus Muslims believed there was no sense in trying to avoid sick people, and the emphasis was on caring for one's family. Jewish doctrine attributed death to God's will and promoted the idea that only God could heal someone, so there was less incentive to treat the sick, concludes Hughes and his colleagues.
While religions were influencing peoples' responses to epidemics, the epidemics themselves may have helped shape religions. "When people feel threatened, they tend to form cooperative groups," says Michael Blume, an expert in religious studies at the Friedrich Schiller University of Jena in Germany, who was not involved with Hughes's study. Blume suggests that as people moved into cities, they needed to find a substitute for families, and religion served that purpose. "When you have disease, it's augmenting this process." Particularly among Christians, being part of a congregation ensured some help would be available in times of need, Blume proposes.
Today, that promise of care is helping to shape the religious makeup in Malawi, Hughes reported. Trinitapoli surveyed 3000 people from 1000 villages across that African country, asking questions about religion and AIDS, which affects one in 14 Malawians and is the leading cause of death in adults there. Some regions were Christian communities, others were Muslim, and some were mixed. About 30% of the Christians regularly visit the sick, whereas only 7% of the Muslims do, Hughes reported. The survey also revealed that the prospect of getting help was enticing. In the past 5 years, about 400 of those responding have shifted religions, many of them moving to Pentecostal or the African Independent Churches, places where the promise of receiving care is greater and the stigma of having AIDS is less, Hughes noted.
Linking early epidemics to the emergence of disease is "a bold hypothesis," says Stephen Stearns, an evolutionary biologist at Yale University. However, he contends that the roles of different religions may be more complex and heterogeneous than Hughes has portrayed them and that there may be alternative explanations for the rise of some religions. The rise of upper classes with more time to think about religious questions may have played a role, for example. "But it's good for the field to have this view clearly laid out."