Bruce Rothschild, a rheumatologist at Northeastern Ohio Universities College of Medicine, and Larry Martin, a paleontologist at the University of Kansas, have turned up fossil evidence that forerunners of cows brought the tuberculosis bacterium to North America long before European colonists introduced the disease.
Their analysis of nearly 1,000 ancient skeletons in university and museum collections showed that TB was spreading throughout the Americas via herds of cattlelike beasts called bovids around 75,000 years ago. But when they tallied the bone lesions that are characteristic of tuberculosis, they found that only bovids with origins in Asia—like bison, bighorn sheep, and musk ox—were afflicted. Bovids that were native to the Americas, as well as all other types of mammals, tended to be disease free.
The pair are now studying older bovid skeletons from Asia and Africa for more clues. "We hope to establish exactly when and where the transformation into the disease we call tuberculosis took place," says Martin.