Darwin, evolution, science and archaeology

Posted May 4th, 2009 by Andrea Vianello

There have been few news in 2009 that prompted anyone to write about archaeology in the blog, and I was therefore very pleased to read the latest issue (Vol. 324, issue 5927) of Science magazine. Two important reports have been featured: a research of the genetic roots of Africans led by Sarah Tishkoff of the University of Pennsylvania [available on Vol. 324, Issue 5930] and a report presented by members of the “Global History of Health Project” at the American Association of Physical Anthropologists on the relationship between urbanisation and human health.

Genetic study sheds light on African people

Genetic study sheds light on African people

Both reports use scientific techniques to reach conclusions relevant to archaeology and evolutionary theories feature prominently in both. In 2009 the world is celebrating the 200th anniversary of Charles Darwin and the 150th anniversary of his book “On the Origins of Species”, and therefore the occasion of talking of evolution and archaeology could not be missed.
Although it might seem incredible, Africa has been neglected in the past genetic research in spite of the fact that our own species originated there. Sarah Tishkoff and her team are spearheading research in that field by collecting over a decade 3,194 blood samples from 113 African populations, several located in remote areas. I want to stress that the samples have been collected ethically by asking appropriate permissions and engaging with local communities. In the past, either the rights of remote communities or the research were often sacrificed as if data had to be easy to acquire, and it is therefore most welcome to hear about a successful study of this magnitude having waived neither. The study has evidenced 14 ancestral genetic clusters by using genetic markers from the Marshfield panel of markers. The genetic clusters appear to correspond to linguistic clusters of populations, however a larger study also including material culture and cultural and social practices has not been undertaken. This is something that should concern archaeologists as linking archaeological data to linguistic and genetic data will be necessary to reconstruct properly the development and relationship of different cultures. Tree maps showing the evolution of species and cultures are popular among geneticists and could be adopted and actually shared by archaeologists. The genetic data is somehow limited to longer scales, and therefore is suitable to show the higher variability of African genes since Africa has been inhabited by our species at least for 200,000 years and the out-of-Africa migration probably did not start earlier than 100,000 years ago (non-African populations are more homogeneous having had less time to differentiate). Genetic markers cannot provide much detail of shorter periods and interactions, and the current incomplete use of markers reduces the threshold even further. The opportunity for archaeology to fill in the blanks and provide a detailed picture is obvious. Tishkoff herself noted how language and culture do not always overlap the genetic data (e.g. Khoesan-speakers and Pygmies share the language despite genetic differences), and in all these . Among the other results of the study worth mentioning is the confirmation that the San bushmen of South Africa were one of the first groups to split having one of the most diverse nuclear DNA and confirming previous mitochondrial and Y chromosome studies. Furthermore, it appears that the migration of modern humans out of Africa started in East Africa, located approximately in the area between Sudan (ancient Nubia) and Ethiopia, near the Red Sea. Although the vicinity of Egypt might make the headlines (and indeed crossing continents in the area of the then not existing Suez Canal must have been the primary route out of Africa), I would like to stress how the movement of peoples out of Africa (long range) probably also involved crossing the waters of the Red Sea. The data have been also compared to datasets from African Americans to verify if it was possible to trace back the roots of African-Americans, but the recent genetic mixing of the latter make it currently impossible. Tishkoff casts doubts on ancestry-tracing kits purporting to trace ethnic origins, and this is in line with what was discussed with Keri Brown in one of our own podcasts. Readers interested in genetic studies of human populations might wish to follow also Dienekes’ Anthropology Blog, which announces new papers and collects abstracts.

The second research project presented was a study of human health across European and Mediterranean populations by Richard H. Steckel, Clark Spencer Larsen, Paul W. Sciulli (Ohio State University) and Phillip L. Walker (University of California). A related study of North America had been completed some time ago; other unrelated and small-scale projects such as the “Global Project on the History of Leprosy” also exist. Once again, scientific data provide the best results looking at longer periods, with traditional archaeology still being the primary source of information for short periods. The results demonstrate that the health of European people deteriorated about 3,000 years ago, when agriculture was introduced. It even worsened further during the Classical period and it only reverted course in the last few centuries, most likely thanks to advances in medicine. However, in North America the general heath of the population decreased from the 1950s, and the phenomenon has been associated by the researchers to the increasing incidence of obesity. Leprosy and tuberculosis increased to due the vicinity of livestock to humans and dental health decreased significantly after switching to a grain-based diet rich in sugars and poorer in nutrients. The researchers interpret the data suggesting that the nomadic hunter-gatherers were more likely to suffer from violence and its effects, and access to food was irregular, and therefore people had to choose between health and safety (from violence and famine). I would prefer to stress instead the social character of humans: interacting with different people is a hard-wired necessity for humans, and clearly agriculture and urbanisation helped in that. This is also demonstrated by the almost constant increase of the world population. There is no doubt that an inverse correlation between human health and wealth can be recognised (also considering the case of contemporary North America), and this defies evolutionary theories to some degree, but then the subject here is human beings and we all know that it is a unique subject. Not only humans are affecting their own health, they are also affecting the planet’s health by producing considerable environmental damage. Yet, they seem extremely successful, unchallenged in nature, and unlikely to disappear any time soon. Applying evolutionary theories, one could say that humans have traded in their health and more for other advantages, benefiting from the trade ultimately. This long-term evolutionary thinking, as in the preceding case, can be enriched by archaeology, and therefore it is hoped that archaeologists will be up to the challenge.

See also a second post on this topic.

Credits: Picture created by Andrea Vianello reusing parts of a photograph taken by Nick Lawes and published under a Creative Commons licence in Flickr.