Evolutionary Thoughts

I’m currently writing an essay on the origins and definitions of Anatomically Modern Humans (Homo sapiens species), and it is an endlessly fascinating (and confusing!) topic.  Recent finds and reports have complicated the picture but have also opened up the delightful hominin evolutionary line (Jurmain et al 2011).  It is also necessarily a wide ranging subject with researchers pinpointing various features of AMH throughout the palaeoanthropological record (Jurmain et al 2011, Pettitt 2005, Tattersall & Schwartz 2008).  By seperating out the modern skeletal anatomy, modern behavioural characteristics and genetic information as they appear in the fossil and archaeological record, it is my view that this approach highlights the ever changing nature of what it means to be a modern human.  This triad approach allows the investigator to realise that different aspects of what is typically expressed as AMH traits (Tattersall & Schwartz 2008: 50), whilst taken as a whole, can also be expressed at differing times due to several factors.

From our earliest anatomically modern traits described in the crania of Omo Kibish 1 & 2 from 195,000 years ago (Pettitt 2005), to cultures and symbolic behaviour attributed to populations throughout Africa by 100,000 years ago, and the evidence of the first dispersals of AMH out of Africa around 80,000-60,000 years ago (Wood 2005), it is clear that AMH have spread far beyond their homeland.  However the continuing work of researchers in Africa and elsewhere in the world has also highlighted the rentention of archaic features in certain AMH populations; examples include the intriguing Iwo Eleru crania found in Nigeria (Harvatie 2011, and Dienekes’ Anthropology post here) and the recently described Chinese skeletal remains reporting a complex evolutionary history of East Asian AMH (Curnoe et al 2012).  This can be attributed to various reasons, such as the admixture of those AMH with archaic hominids or population isolation.

Recent email communication with my friend and fellow blogger Confusedious has also highlighted the varied genetic changes in recent populations of Homo sapiens.  His excellent post on gene culture coevolution is a detailed and elegant essay discussing rapid and modern genetic changes in H. sapiens regarding disease loading in populations, gene expression and selective gene adaptation; largely as a result of agricultural uptake and increased population density (Barnes et al 2011, Hawks et al 2007).  Recent molecular work on the origin of TB (Smith et al 2009 & previously wrote about here by me) has helped highlight the need for a nuanced approach in treating the disease in modern populations.  Examples include indigenous Papua New Guinea people and the Torres Strait Islanders, who do not have a genetic history of coevolution with the disease from the practise of intense animal husbandry, and who are now threatened by today’s demographic pressure and population expansion of those who do, and who have selectively adapted to it (Barnes et al 2011).

In conclusion, the gestalt of the Homo sapiens species may be instantly recognizable to some (Tattersall & Schwartz 2008), but there are a number of factors that intertwine, such as skeletal morphology, genetic change and behavioural adaptations, that produce a species that emerged roughly 200,000 years ago and are continuing in their adaptations to this world.

Bibliography:

Barnes, I., Duda, A., Pybus, O. G. & Thomas, M. G. 2011. Ancient Urbanization Predicts Genetic Resistence to Tuberculosis. Evolution. 65 (3): 842-848.

Curnoe, D., Xeuping, J., Herries, A. I. R., Kanning, B., Tacon, P. S. C., Zhende, B., Fink, D., Yunsheng, Z., Hellstrom, J., Yun, L., Cassis, G., Bing, S., Wroe, S., Shi, H., Parr, W. C. H., Shengmin, H. & Rogers, N. 2012. Human Remains from the Pleistocene-Holocene Transition of Southwest China Suggest a Complex Evolutionary History for East Asians. PLoS ONE. 7 (3): 1-28. e31918. doi:10.1371/journal.pone.0031918

Harvati, K., Stringer, C., Grun, R., Aubert, M., Allsworth-Jones, P., & Folorunso, C. A. 2011. The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology. PLoS ONE. 6 (9): e24024. doi:10.1371/journal.pone.0024024

Hawks, J., Wang, E. T., Cochran, G. M., Harpending, H. C. & Moyzis, R. K. 2007. Recent Acceleration of Human Adaptive Evolution. Proceedings of the National Academy of Sciences. 104 (52): 20753-20758.

Jurmain, R., Kilgore, L. & Trevathan, W. 2011. The Essentials of Physical Anthropology, International Edition.Belmont:Wadsworth.

Pettitt, P. 2005. ‘The Rise of Modern Humans’. In Scarre, C. (ed) The Human Past: World Prehistory & the Development of Human Societies. London: Thames & Hudson. pp 124-175.

Smith, N. H. Hewinson, R. G. Kremer, K. Brosch, R. & Gordon, S. V. 2009. Myths and Misconceptions: The Origin and Evolution of Mycobacterium tuberculosis. Nature Reviews: Microbiology. Vol 7: 537-544.

Tattersall, I. & Schwartz, J. H. 2008. The Morphological Distinctiveness of Homo Sapiens and Its Recognition in the Fossil Record: Clarifying the Problem. Evolutionary Anthropology. 17: 49-54.

Wood, B. 2005. Human Evolution: A Very Short Introduction. Oxford: Oxford University Press.

The Origins of Tuberculosis & Smallpox

The following articles cited were brought to my attention by the good work of Confusedious: A Science Blog, and his entries on TB and its  possible origin.

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).

Compression Of Vertebrae As An Effect Of TB

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).

The Effects of Smallpox Decimated The Americas When The Europeans Helped Spread the Disease in the 16th Century, As Depicted In This, The Florentine Codex.

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.

Bibliography:

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 2^nd.  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.