Farming spread across Europe from Southwest Asia between 6500 and 4000 BC, but interactions between the indigenous Mesolithic hunter-gatherers and incoming Neolithic farmers are poorly understood. The general view is that hunter-gathering disappeared soon after the arrival of agriculture, but whether the hunter-gatherers took up farming themselves or simply died out remains uncertain.
In order to investigate relationships between foragers and farmers, researchers examined Mesolithic and Neolithic samples from Blätterhöhle, a cave site near Hagen in North Rhine-Westphalia, Germany (Bollongino, et al., 2013). The cave contained the remains of around 450 Neolithic and Mesolithic individuals. It is likely that it was a burial ground, and that these individuals were deposited there deliberately. Radiocarbon dating has revealed two phases of occupation: a Mesolithic occupation from 9210 to 8340 BC, and a Late Neolithic occupation from 3986 to 2918 BC.
Stable isotope analysis and ancient mitochondrial DNA extraction was carried out on the bones and teeth of 29 individuals. Isotopic ratios of sulphur, nitrogen and carbon in human remains can provide an insight into the diet of an individual while they were alive. Mitochondrial DNA can trace maternal ancestry.
Of the 29 individuals sampled, 25 yielded usable mitochondrial DNA; five from the Mesolithic occupation and 20 from the Late Neolithic occupation. The five Mesolithic-era individuals all belonged to mitochondrial haplogroup U, in common with other pre-Neolithic hunter-gatherers of central, eastern and northern Europe. More unexpectedly, twelve of the Neolithic-era individuals also belonged to haplogroup U. This haplogroup is rare among Late Neolithic farmers, and suggests a surprising persistence of Mesolithic maternal ancestry. The remaining eight individuals belonged to typical Neolithic haplogroups.
Stable isotope analysis indicated the existence of three distinct groups. The first, comprising the Mesolithic-era individuals, subsisted on a diet of wild foods typical of that found at other inland Mesolithic sites. The second group comprised Late Neolithic individuals with a diet of domesticated animals typical of German Neolithic sites. The third group was also from the Late Neolithic, but diet was unusual: low in plant and animal protein and high in freshwater fish.
The members of this third group all belonged to mitochondrial haplogroup U, whereas members of the contemporary second group were a mixture of Mesolithic and Neolithic haplogroups. Thus it appears that a group of fisher-foragers were living alongside a group of farmers in the fourth millennium BC, which is around 2,000 years after agriculture reached central Europe. That both groups used the Blätterhöhle cave site at the same time indicates that they were near-neighbours.
Ethnographic data shows that such communities do live side by side, commonly exchanging food; for example cereals for fish. While forager women do marry into farming communities, the reverse is very rare as women from farming communities regard it as marrying down. The mitochondrial results are consistent with the ethnographic picture: no Neolithic haplogroups were found among the fisher-foragers; but the Mesolithic haplogroup U was present among the farmers.
It is unclear just how prevalent such forager communities were in Late Neolithic Europe, but the Blätterhöhle results are the strongest indication yet that such genetically-distinct communities persisted long after the arrival of farming. The ultimate fate of these communities remains uncertain. The authors of the study suggest that some groups may have eventually changed over to farming, although it has been suggested that incoming farmers would rapidly appropriate all the prime farmland, making such a switch problematic (Bellwood, 2005).
References:
1. Bollongino, R. et al., 2000 Years of Parallel Societies in Stone Age Central Europe. Science 342, 479-481 (2013).
2. Bellwood, P., First Farmers (Blackwell Publishing, Oxford, 2005).
