The Arrival of TB

Quickly after the Europeans arrived in America in the 1600s, tuberculosis epidemics scourged many tribes of Native Americans. It has long been argued that this disease was absent from the New World before 1492 and that the Europeans were the first to transmit it to the Native Americans. With no prior exposure and little natural immunity against the disease, the indigenous people would be highly susceptible to the disease.

Some anthropologists, however, challenged this conventional view, based on tuberculosis-like lesions that were found in a few skeletons and mummified remains. This, they claimed, suggests that the disease was present in America before the arrival of the Europeans. On the other hand, there are other conditions that can cause such lesions. So the origin of tuberculosis in America remained highly controversial.

An Answer Through PCR

In 1994, a pathologist named Arthur C. Aufderheide and molecular biologist Wilmar Salo attempted to solve this mystery. They did this by investigating the remains of a Peruvian women that died over 1000 years ago and was naturally mummified. Samples of the right lung and lymph nodes were removed, and a polymerase chain reaction (PCR) was performed on these samples. This PCR was used to search the samples for DNA of Mycobacterium tuberculosis, the bacterium that causes tuberculosis.

The PCR technique is able to produce copies of a 97 bp (base pair) fragment of DNA when applied to DNA from the modern-day bacterium. By applying the PCR to the samples of this 1000 year old mummy, an identical piece of DNA was found. This unambiguously demonstrates that tuberculosis was present in this woman, long before the Europeans arrived.

But What About the Epidemics?

Although the Europeans were not the first to transmit TB to the Native Americans, they were still the most likely cause of the epidemics. Their settlement on the new continent was a highly disruptive event for many indigenous societies, often causing mass displacements of people and radically altering their traditional lifestyle. These stressful, accompanied by the crowding and malnutrition in the reservations, were probably responsible for lowering the resistance of many Native Americans and contributed greatly to the spreading of tuberculosis.

This discovery of tuberculosis in the mummified remains of a woman that died over 1000 years ago, clearly illustrates the power of the PCR technique, which has quickly become one of the most often used techniques in molecular biological research.