Evolutionary Thoughts

7 Apr

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 anatomymodern 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 tuberculosisNature 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.

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7 Responses to “Evolutionary Thoughts”

  1. confusedious April 14, 2012 at 12:10 pm #

    An excellent post! Thank you kindly for mentioning my work!

    Finding a way to define what is or is not AMH is incredibly difficult (and in many ways so like the race-concept drama one often finds oneself in when critiquing forensic anthropological work), so I think you are wise to take a multifaceted approach. All the recent evidence of introgression with archaics has also complicated the picture, but at the same time made it infinitely more interesting. I’d love to hear more about what you find out on the subject as later this semester I am giving a presentation on what Prof. Groves has referred to as ‘alien DNA in our genome’ a topic which dips a toe into what it means to be AMH. I’ve been finding that even defining what it is to be Homo becomes tricky when one considers the complex speciation model put forward by Patterson et al. back in 2006, with its central evidenced notion that the human X chromosome is in fact more Pan than Man! I’ve linked the paper below in case it is of interest to you (sorry the DOI didn’t seem to be working):

    http://www.nature.com/nature/journal/v441/n7097/abs/nature04789.html

    • These Bones Of Mine April 14, 2012 at 1:39 pm #

      Excellent, thank you very much! I am slightly worried about this essay, I’ve finished it now, just 3300 words or so with a few tables and diagrams. I’ve mentioned Denisovans and Neandertals, and the genes and modern day DNA etc, but not much as I didn’t really have the space! Thanks for the paper, I shall take a look at it! I’ve ended the essay on a note that perhaps the fossil record is actually quite complete in comparison to the chimpanzee fossil record, and perhaps it’ll be better to put AMH in a full evolutionary context.

    • These Bones Of Mine April 14, 2012 at 1:45 pm #

      That paper is actually ideal for what I propose at the end of the essay; thank you so much! The short communication back is interesting however; http://www.nature.com/nature/journal/v452/n7184/full/nature06805.html

  2. Ajetomobi rotimi June 2, 2012 at 11:22 pm #

    yeah, great effor had been laid but some of the facts that actualize issues on iwo eleru would have been shared by the people at the most initial sphere of iwo eleru. Though it located in my base and patched shelter of our forefather of which much have felted and factual as regards iwo eleru buria if not but one of the most oldest man in history. How did they discover the spot? How did the spot respond to day and nigh? Are there any other related features? What about ‘oke eleru’? thanks.

    • These Bones Of Mine June 3, 2012 at 5:36 pm #

      Hello Ajetomobi,
      All the information should be in the bibliography regarding the Iwo Eleru individual. I’ve linked the PLoS one paper and it can be found in the blog post. let me know if you have any questions that aren’t answered by it. Cheers, hope you are well!

      • Ajetomobi rotimi June 4, 2012 at 7:24 am #

        I red through the blog post perhaps great efforts. It answered a lot of questions, kudos to the Morgphometric analysis. Despite their real lack of knowledge of human evolution in that region, as well as others. There ‘re people in the region before excavation of the fossils in 1965 that described how fairy dawn the spot appeared to be in the mid night. How could this be approached in their analysis? Morealso, about 3km to Iwo Eleru is located Oke Eleru where there are existing fossils of which no effort has been made. Whereas i looked at how abandon those Two sites looked like it shouldn’t be. How could development come to all these feature sites? I hope in the next stage research extending studies to the Iwo Eleru mandible and postcranian, and to comparative materials such as those from Ishango. Likewise I would have loved to to read your essay on the fossil record in comparison to the chinpampanzee fossill record. Great effort thanks.

        • These Bones Of Mine June 4, 2012 at 7:09 pm #

          Hi again,
          Cheers for the reply! I’m not really sure how they could incorporate the light, perhaps consult some other experts? I think its all a matter of funding really, and investigation- perhaps you should email some of the people in the article? Hopefully there should be further investigations as it is pretty interesting! It is really my pleasure my friend. Once the essays are marked and I’ve finished my degree here, I’ll post my essay- though it is more to do with describing the troubles of defining anatomically modern humans, it does mention chimpanzees. Thanks again Ajetomobi.

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