The Mummy's Tale

The ghosts of Columbus and his fellow European explorers can breathe a bit easier. They have long been accused of slaying New World natives not just with swords but also with germs. Supposedly, the sailors -- and eventual settlers -- brought with them the bugs for illnesses unknown in the Americas, including smallpox, measles, influenza, malaria and tuberculosis. Never having been exposed to these ailments, natives had no immunity. Now, though, the European invaders have been exonerated as the carriers of at least one disease to the New World. Scientists said last week that they had found DNA from the TB bacterium in the mummified remains of a woman who died in the Americas 500 years before Columbus set sail from Spain.

Paleopathologists had suspected that TB existed in the New World before 1492. Ancient skeletons, for instance, have bone lesions that resemble those caused by TB. But the DNA discovery, reported in the Proceedings of the National Academy of Sciences, is the first firm proof of TB's longevity in the Americas. "It's about the best evidence you could hope for," says biochemist Wilmar Salo of the University of Minnesota, who was on the research team.

The genetic material comes from one of several hundred bodies, mummified by natural forces, that were unearthed in 1989 and 1990 by University of Chicago anthropologists from the cemeteries of Chiribaya, an agricultural community along the coast of what is now southern Peru. Pathologist Arthur Aufderheide of the University of Minnesota, who autopsied the mummies, was intrigued by one woman he judged to have been 40 to 45 years old, an advanced age for her society. But he expected to find little else remarkable because the body was so poorly preserved. To his surprise, when he opened the chest, he found a lump on the lung and another two in the lymph nodes -- a common sign of TB infection.

Back in the U.S., Aufderheide carried thumbnail-size tissue samples he had taken from the woman to his colleague Salo, the biochemist. Using a new technique of dna analysis called polymerase chain reaction, the Minnesota researchers cloned billions of copies of the ancient genetic material. Then they identified a fragment of dna that is found only in TB bacteria.

"The native Americans had so much TB in early colonial times," speculates Aufderheide, "because they were crowded into towns and had much poorer living conditions than before." TB spreads rapidly among people with immune systems weakened by malnutrition and poor sanitation. Among the mummies of rural Chiribaya, few showed any sign of TB infection, and the woman from whom TB DNA was isolated did not die of the disease.

The big mystery: How did TB get to the Americas? Did people migrating from Asia across the Bering Sea land bridge take the disease to the new land? Those travelers, thousands of years earlier than Columbus, may have carried the answer to their graves. If so, scientists may one day unearth it.