Pre-Pottery Neolithic Central Anatolia and the effects of a Late Neolithic bottleneck in sheep
From the Stone Age to today: Genetic analyses reveal history of domesticated sheep.
Through the statistical analysis of hundreds of DNA samples from Stone Age and modern sheep, an international research team with the participation of the ÖAI has reconstructed the domestication, distribution and population development over the last 12,000 years. The results were published in the journal “Science Advances”.
Sheep are among the first animals to be domesticated by humans. Excavations of the Stone Age settlement of Aşıklı Höyük in Central Anatolia (present-day Turkey), which is around 10,300 years old, show early traces of sheep being kept as livestock. An international research team has succeeded in isolating mitochondrial DNA from the bone remains and comparing them with samples from other regions and later eras.
Sheep populations reconstructed over 10,000 years ago
Aşıklı Höyük was inhabited for 1,000 years, which means we have an incomparable treasure trove of genetic information about a very early, domesticated sheep population. The genetic experts isolated mitochondrial DNA, which is only passed on from the mother, from bones and combined it with samples from other archaeological sites in Anatolia, the Levant, the Caucasus and Europe. By comparing it with the mitochondrial DNA of modern sheep from 15 countries, we were able to reconstruct the development of sheep populations in Europe and Asia over the past 10,000 years,” says Barbara Horejs, scientific director of the Austrian Archaeological Institute, who contributed to the work with her team for the Austrian Academy of Sciences (ÖAW).
The researchers’ analyses show that genetic diversity among the domesticated sheep in Aşıklı Höyük was high over the entire thousand-year settlement period, although many domestication theories predict a genetic bottleneck for early livestock populations in herds. “Five different maternal lineages occur with a relatively equal distribution over the entire 1,000 years, although archaeological traces suggest that husbandry and use for meat production intensified during this phase. One possible explanation for this is that a fairly large population was regularly increased by crossbreeding with wild animals,” says Horejs.
Stone Age genetic material in today’s sheep
In modern sheep populations in Europe and Asia, only two of the five mitochondrial genetic lines that were present in Aşıklı Höyük can be found. The approximately 60 million sheep that are kept in Europe today belong almost exclusively to haplogroup B. “Models of population developments show that there must have been a genetic bottleneck later on, sometime between the end of the settlement of Aşıklı Höyük and the introduction of domesticated sheep in Europe around 8,500 years ago. Our samples from Çukuriçi Höyük, which we found during excavations of this pioneer settlement of the oldest farming groups on the Turkish Aegean coast and which ÖAW archaeozoologist Alfred Galik examined, belong to exactly this period. The genetic results of the domesticated sheep from Neolithic Çukuriçi in our study belong to haplogroup B and support this interpretation,” says Horejs.
Statistical analyses show that the population must have declined by a factor of about ten during this phase. In the past 5,000 years, the population in Europe has increased again more than tenfold. “Our research shows that early livestock farming developed quickly, with stable populations, a lively exchange of animals between settlements and regular crossbreeding with wild animals. A genetic bottleneck only occurred with the spread of livestock farming from Anatolia to Europe and Asia, which occurred parallel to the spread of agriculture,” says Horejs, emphasizing: “Future analyses of the complete sheep genome, beyond mitochondrial DNA, can provide further important information about populations and migrations of humans and animals in this crucial period of our history.”
Current research by Horejs with her new model of “multispecies mobility” promises to provide insights into the importance of different species in the transformation of hunter-gatherer groups into sedentary farmers.
Pre-Pottery Neolithic Central Anatolia and the effects of a Late Neolithic bottleneck in sheep
HEAS Members involved: Barbara Horejs
For more information contact Astrid Pircher