Tyrone Hayes stands out in the overwhelmingly white field of biology, and his skin color isn't the half of it. To use his own idiom, Hayes is several standard deviations from the norm. At the University of California at Berkeley, he glides around his lab wearing nylon shorts and rubber flip-flops, with a gold hoop in one ear and his beard braided into two impish points. Not counting his four inches of thick, upstanding hair, Hayes is just over five feet tall, with smooth features and warm eyes. He drives a truck littered with detritus human, amphibian, and reptilian. He keeps his pocket money in a baby's sock. "Hey, wassup?" he'll say to anyone, from the president of the United States on down. He can't help the informality, he says. "Tyrone can only be Tyrone."
Hayes, 35, is a professor at Berkeley, where he has taught human endocrinology since 1994. His research centers on frogs, of which he keeps enormous colonies. Frogs make convenient study subjects for anyone interested in how hormones affect physical development. Their transformation from egg to tadpole to adult is rapid, and it's visible to the naked eye. With their permeable skin, frogs are especially vulnerable to environmental factors such as solar radiation or herbicides. That vulnerability has lately garnered Hayes more attention than his appearance ever has.
The controversy began five years ago, when a company called Syngenta asked Hayes to run safety tests on its product atrazine. Syngenta is the world's largest agribusiness company, with $6.3 billion in sales of crop-related chemicals and other products in 2001 alone. Atrazine is the most widely used weed killer in the United States. To test its safety, Hayes put trace amounts of the compound in the water tanks in which he raised African clawed frogs. When the frogs were fully grown, they appeared normal. But when Hayes looked closer, he found problems. Some male frogs had developed multiple sex organs, and some had both ovaries and testes. There were also males with shrunken larynxes, a crippling handicap for a frog intent on mating. The atrazine apparently created hermaphrodites at a concentration one-thirtieth the safe level set by the Environmental Protection Agency for drinking water.
The next summer Hayes loaded a refrigerated 18-wheel truck with 500 half-gallon buckets and headed east, followed by his students. He parked near an Indiana farm, a Wyoming river, and a Utah pond, filled his buckets with 18,000 pounds of water, and headed back to Berkeley. He thawed the frozen water, poured it into hundreds of individual tanks, and dropped in thousands of leopard-frog eggs collected en route. To find out if frogs in the wild showed hermaphroditism, Hayes dissected juveniles from numerous sites. To see if frogs were vulnerable as adults, and if the effects were reversible, he exposed them to atrazine at different stages of their development.
