Two months into our project, we have been busy. The first task was to re-write a large grant proposal for the ERC in order to secure funding. This would enable us to broaden out the chronological scope of the project and look at changes in social responses to pregnancy, birth and childrearing over three millennia. Keep your fingers crossed!
On the plus side of this rather tedious job was that we could re-view and re-fine some of the methodology employed in the project. Cemetery demographics, for example, play a larger role in the project now. It is indeed interesting to see that from the age and death profile of all buried individuals in a cemetery we can infer certain demographic characteristics. Most interesting for our project is at what age women, on average, gave birth to their first child, and how many children they had in total.
In the Iron Age, for example, there seems to be a large difference between the Mediterranean and northern Europe, with women giving birth the first time up to ten years later on average. Reasons may include worse nutrition and later menarche, but socio-economic structures are probably the largest contributing factor. Delaying marriage until a certain level of prosperity and security has been reached sound familiar from our own society today. We do not know a lot about marriage and inheritance rules in prehistory, although both might have had a large impact on what we see in the archaeological record.
The second task was to get an overview of our case studies and select the best cemeteries available for DNA testing. We are, for this reason, compiling a site gazetteer with short descriptions of the burial sites and their characteristics. We are focussing on burials of women and children together, and burials of infants and juveniles of unclear sex. Both the archaeological documentation has to be reliable and the preservation of bones has to be sufficient.
In terms of the archaeology, Katharina populates one spreadsheet per site with data on the graves, including grave construction, grave goods and co-buried individuals. Doris checks the physical anthropology data published and visits the boxed individuals to check the conditions of the bones and how much of them is really preserved.
We are working primarily with museum specimens from the Natural History Museum in Vienna that have been excavated, washed, stored and generally handled a lot. How much DNA is preserved in the hard parts of the body (femur, teeth and petrous portion of the temporal bone) is hard to tell from just looking at the bones. It very much depends on the conditions the bones had been buried in for the thousands of years they were in the soil, how much they were exposed to heat, water and chemicals. There is no real way of knowing before the samples are run. As DNA testing is a destructive method, we need to take samples of small size and try to preserve as much of the skeleton as possible. The samples then have to be cleaned of all possible contamination by mechanical and chemical means.
With our geneticist Walther Parson we decided on a strategy that involves taking three samples of well preserved bones per site for a test run. If aDNA can be yielded at all, we branch out and test all the individuals we are interested in, if there is no aDNA preserved, we move on to another site. It is a blessing and a curse that there are thousands of individuals to choose from Bronze Age Austria – some hard decisions have to be made.
The practicalities of sampling are another issue. Not many people will have a precision bone saw on top of this week’s shopping list J
Bocquet-Appel, J.-P., and C. Masset. 1982. Farewell to Paleodemography. Journal of Human Evolution 11: 321-333.
Burmeister, S., and M. Gebühr. in press. “Demographic aspects of Iron Age societies ” in C. Haselgrove, P.S. Wells, and K. Rebay-Salisbury (eds) The Oxford Handbook of the European Iron Age. Oxford: Oxford University Press.
Robbins, G. 2011. Don’t throw out the baby with the bathwater: Estimating fertility from subadult skeletons. International Journal of Osteoarchaeology 21(6): 717-722.
Chamberlain, A. 2006. Demography in Archaeology. Cambridge Manuals in Archaeology. Cambridge: Cambridge University Press.