Important Discoveries of 2008 - Human TB - Tracking a Disease

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(Courtesy I. Hershkovitz and E. Galili)

We covered the identification of tuberculosis in human remains found at Atlit-Yam, a submerged site off the coast of Israel, in our "World Roundup" in the January/February 2009 issue. Yes, we now have TB identified 3,000 years earlier than before, but this is a huge story when you look beyond the immediate news. First, there's how the combination of anatomical observation and genetics is proved TB was present. When Israel Hershkovitz, from Tel-Aviv University, examined the remains, of what may be a mother and baby who lived in the 9,000-year-old Neolithic village, he saw what appeared to be bone lesions typical of TB. That was of interest because Atlit-Yam dates from the beginnings of cattle domestication, but one theory of TB's origins is that the human form of the bacteria (Mycobacterium tuberculosis) jumped to human beings from cattle after people and the animals had been in close contact for some time. Helen Donoghue and Mark Spigelman of University College London found M. tuberculosis DNA in the bones and (for that high-tech touch) used "high performance liquid chromatography" to identify cell wall lipids from the bacteria, confirming the DNA results.

But there's more. Because the DNA in the 9,000-year-old samples was distinct from modern strains, it helped the genetics researchers calibrate how quickly M. tuberculosis changes over time. According to Donoghue, it "indicates an extremely long association with humans." A deep history for human TB makes sense. Recent genetic studies of TB-like bacteria in East Africa suggest a long history for the human pathogen, and there is a possible 500,000-year-old case from a Homo erectus fossil found in Turkey, but that is debated. There's also the fact that TB is present in the New World before the European colonization (see "More TB in Peruvian Mummies"). Taken together, the fossil, genetic, and archaeological evidence points to a long history of human infection by TB, perhaps preceding the expansion of modern humans from Africa and likely before the colonization of the New World from Asia by Paleolithic peoples.

More Top Discoveries of 2008