While previous studies of TB bacteria's DNA have estimated that the lung disease originated about 35,000 years ago, researchers at the Pasteur Institute in Paris believe it could have been present in early hominids up to 3 million years ago.

"Our results change the current paradigm of the recent origin of tuberculosis," said author Veronique Vincent.

Most TB cases are caused by Mycobacterium tuberculosis. Vincent and colleagues examined cases of the disease from East Africa in which colonies of TB bacteria appear physically different from those that cause TB elsewhere. After analyzing genetic data from the different strains, the authors surmised that the ancestors of these bacterial strains were progenitors of Mycobacterium tuberculosis as well. That suggests that both strains emerged from a species of bacteria possibly up to 3 million years old, they reported.

"Tuberculosis could thus be much older than the plague, typhoid fever or malaria, and might have affected early hominids," concluded the researchers. Thus, the expansion of TB to the rest of the world may have coincided with waves of human migration out of Africa.

The full study, "Ancient Origin and Gene Mosaicism of the Progenitor of Mycobacterium tuberculosis," was published in the journal PloS Pathogens (2005;1(1):0001-0007).

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