Surprising Origins of Tuberculosis & Smallpox
Recent genetic investigations into the origin of the above diseases, of the chromosomes in TB and the study of smallpox’s ‘biological clock’, has revealed interesting information regarding their origin. TB and Smallpox were previously thought caused or at least had its early origins during the domestication of animals, and by the dense urbanisation of human populations, first seen during the Mesolithic to Neolithic transition (Tuberculosis- Barnes et al 2011, Larsen 1997, Roberts & Manchester 2010, Smith et al 2009, Smallpox- Li et al 2007, Waldron 2009).
Tuberculosis was originally thought to be spread from bovine at the period of domestication, with the strains M. Tuberculosis and M. Bovis to be considered the main organisms for TB infection in humans. New genetic research has led to distinguish that M. Tuberculosis did not evolve from M. Bovis at the time of domestication of animals as a direct zoonosis; however it must be remembered that ‘it is probable that a necessary condition for its transference from animal to human is the close association between the two’ (Roberts & Manchester 2010: 184, Smith et al 2009). I’d imagine the intensification of the Neolithic domestication undoubtedly led to higher rates of cross-species infection. Research has also shown that the Mycobacterial Tuberculosis strain appeared some 15,300-20,400 years ago, well before the domestication of the earliest animals (Roberts & Manchester 2010: 185). However there is no doubting the record that during the Neolithic, and up to the present day, that TB has damaged numerous lives. The effects of TB on the human body can produce results found in osteological remains (Waldron 2009). This will be discussed in a later blog entry on diseases found in human bones.
The threat of smallpox, a unique infectious disease to humans, was wiped out in AD 1980, but its origins are mysterious. As Roberts & Manchester (2010: 181) note smallpox (Variola major or minor) ‘would obviously need highly populated urban areas for its success…and it is unlikely it was a problem until urbanization occurred’. Recent genetic investigations into the origin of the Variola major/minor have discovered that it likely diverged from an ancestral African rodent-borne Variola-like virus either 68,000 to 16,000 BP (Li et al 2007). However, it is well known that in its most virulent form in humans as smallpox, it has ravaged human urbanised populations for at least 2000 years, and is definitely dated to 10,000 BP. Curiously, from documentary data and archaeological data, it seems there is a particular lacking of recorded smallpox cases in ancient Greece and ancient Rome (Roberts & Manchester 2010).
New genetic data is providing the backdrop for how infectious diseases spread, and more about their origin. It is also helping scientists develop past population pathways for infection routes and rates (Jurmain et al 2011).It is apparent that new genetic data has opened up a whole raft of new research potentials into the origins and evolution of tuberculosis, and the relationship before, during and after the domestication of animals.
Barnes, I.Duda, A. Pybus, O. G. Thomas, M. G. 2011. ‘Ancient Urbanization Predicts Genetic Resistance To Tuberculosis’. In Evolution. 65 (3): 842-848. Blackwell Publishing: London.
Jurmain, R. Kilgore, L. & Trevathan, W. 2011. Essentials of Physical Anthropology International Edition. London: Wadworth.
Li, Y. Carroll, D. S. Gardner, S. N. Walsh, M C. Vitalis, E. A. & Damon, I. K. 2007. ‘On The Origin of Smallpox: Correlating Variola Phylogenics with Historical Smallpox Record’. In PNAS. 104 (40). October 2nd. 15,787-15,792.National Academy of Sciences: Wisconsin.
Roberts, C. & Manchester, K. 2010. The Archaeology of Disease Third Edition. The History Press: Stroud.
Smith, N. H. Hewinson, R. G. Kremer, K. Brosch, R. & Gordon, S. V. 2009. ‘Myths and Misconceptions: The Origin and Evolution of Mycobacterium tuberculosis’. In Nature Reviews: Microbiology. Vol 7. 537-544. Macmilan Publishers Limited: London.
Waldron, T. 2009. Palaeopathology: Cambridge Manuals in Archaeology. Cambridge:Cambridge University Press.