Phase 2: Continuing CEACB projects (phase 1): Project 021|
Spatial analysis of cultural change in the early Neolithic of Europe
James Steele (AHRC CECD, Institute of Archaeology, University College London)
Lee Hazelwood (Archaeology, University of Southampton)
Thembi Russell (PhD student) Hilary Snelling (PhD student)
PROJECT FUNDING: 50% PDRA, PHD
There is a long tradition of using radiocarbon dates to map the spread of farming in Europe at the continental scale. Clark (1965:67) discerned a pattern of spread into Europe along the Danube from an origin in the South East. Ammerman & Cavalli-Sforza (1984) conjectured that this pattern was produced by a gradual process of spatial population expansion and replacement. Support for this 'demic diffusion' model came with the SE-NW gradient in the first Principal Component of variation in allele frequencies of Europeans on a synthetic gene map. The steepness of this cline in gene frequencies was modelled as a function of the rate of reproductive mixing with hunter-gatherers.
Subsequent work has transformed this simple picture. Identical travelling waves for the spread of farming can be generated by demic expansion, demic diffusion, or by trait adoption-diffusion (Aoki et al. 1996). Archaeologists have pointed out the very different rates of spread of farming in different regions of Europe, and point out that synthetic gene maps contain no information about the chronology of dispersals. Furthermore, synthetic gene maps can potentially produce clines even in spatially random data (Sokal et al. 1999), and genuine clines in gene frequencies can be produced by population replacement with successive founder effects (cf. Barbujani et al. 1995), by demic diffusion with acculturation (cf. Rendine et al. 1996), or by gradients in natural selection pressures related to economic strategy (Fix 1997).
Clearly, we need to re-evaluate the radiocarbon record if we wish to test alternative models of the demography of the Neolithic transition. The purpose of this project is to collect a spatial database of radiocarbon dates for the later Mesolithic and early Neolithic of Europe, roughly 9000-5000 BP, which covers the later Mesolithic in southeast Europe to the earlier Neolithic in northwest Europe, along with the contexts of the dates, the material dated and economic and cultural associations.
Spatial analyses of the accumulation of dates in the radiocarbon database confirms a correlation between date of earliest occurrence and distance from an assumed source in Europe. However, this could have resulted either from a cultural diffusion through a pre-existing population or a wave of population replacement. The gradients in gene frequencies plotted in synthetic gene maps can also be explained by multiple mechanisms, of which demic expansion is only one.
Additional analyses plotted summed distributions for Mesolithic and Neolithic radiocarbon dates by region (see powerpoint animation). In areas where demic diffusion is predicted to have occurred, a more abrupt transition may be visible. However, the underlying causes of such abruptness (if it is indeed a genuine pattern) remain to be investigated. The environmental factors differentiating regions of probable demic diffusion from those of probable adoption-diffusion also need to be examined in terms of their implications for forager and farmer demography.
FINAL PROJECT REPORT:
Final Report Not Received
|•||Thembi M. Russell (2004).|
The spatial analysis of radiocarbon databases: the spread of the first farmers in Europe and of the fat-tailed sheep in Southern Africa. BAR International Series (S1294). Archaeopress: Oxford.
|•||Russell, T. and J Steele (2002).|
Visualizing the Neolithic Transition in Europe. CAA 2001. Gotland: BAR Int. S.