To examine the possible benefits from eating earth, researchers at Cornell University analyzed reports from missionaries, plantation doctors, explorers, and anthropologists to put together a database of more than 480 cultural accounts of geophagy -- the eating of earth.

    The database includes as many details as possible about the circumstances(情况环境) under which earth was consumed, and by whom. The researchers could then use patterns in the data to evaluate each potential explanation.

    Studies in the database indicate that geophagy is common even when food is plentiful. Moreover, when people eat dirt they tend to eat only small quantities that are unlikely to fill an empty stomach.

    The database shows that geophagy is documented most commonly in women in the early stages of pregnancy and in pre-adolescent children. Both categories of people are especially sensitive to parasites and pathogens, according to the researchers.

    In addition, geophagy is most common in tropical climates where foodborne microbes are abundant. Finally, the database shows that people often eat earth during episodes of gastrointestinal stress.

    It's unlikely the intestinal problems are caused by the dirt itself because the type of clay people usually eat comes from deep in the ground, where pathogens and parasites are unlikely to contaminate it. Plus, people usually boil the clay before eating it.

    More study would be helpful to confirm the protection hypothesis, the researchers say, but the available data at this point clearly support it over the other explanations for eating earth.

    "We hope this paper stimulates (more) research," said Sera Young, a researcher at Cornell University and the study's lead author. "More importantly, we hope readers agree that it is time to stop regarding geophagy as a bizarre, non-adaptive gustatory mistake.""With these data, it is clear that geophagy is a widespread behavior in humans ...that occurs during both vulnerable life stages and when facing ecological conditions that require protection."The study is appearing in the June issue of The Quarterly Review of Biology.(本文由在线英语听力室整理编辑)