Sheep bones discovered during archaeological excavations at six different sites across Anatolia have shed light on the domestication of sheep thanks to the deoxyribonucleic acid (DNA) analysis in a new study led by the Middle East Technical University (ODTÜ) and Hacettepe University.
Samples of the examined sheep were obtained from Tepecik Çiftlik Mound, Pınarbaşı Mound, Boncuklu Mound, Canhasan III Mound, Ulucak Mound and Barcın Mound, where excavations were carried out within the scope of the "Neogene" project, supported by the European Research Council (ERC) and the Scientific and Technological Research Council of Turkey (TÜBITAK) 1001 projects.
An international team of 42 geneticists, archaeologists and anthropologists from 17 universities across seven countries took part in the study.
Sheep were one of the first domesticated livestock in the Neolithic period, about 10,000 years ago. Archaeological data showed that domestication of sheep took place in the Middle East, in a region that included eastern and central Anatolia.
In the millennia following domestication, the domesticated sheep spread to Europe, North Africa, and Central Asia. However, exactly when and how many times the sheep were domesticated and how they evolved after domestication could not be determined until now.
In the study, topics related to the domestication process of sheep that have been intriguing for archaeologists, anthropologists and geneticists, were unearthed through ancient DNA research. Research data showed that sheep might have been domesticated 10,000 years ago in other regions besides Anatolia.
The results of the study, published and announced to the scientific world in the journal Communications Biology, were defined as the most comprehensive ancient sheep genome article ever produced.
The lead author of the study, Füsun Özer, faculty member of the anthropology department at Hacettepe University, stated that they analyzed the bones of sheep found in six archaeological excavations. Explaining that they made DNA analysis of 180 individuals in total, Özer said that ancient genome data could be produced from four of them, and they also studied the mitochondrial DNA of 91 sheep in the study.
Özer noted they observed that the DNA was protected very little in ancient sheep bones, probably due to the cooking of sheep. Özer said that they compared the genome and mitochondrial DNA data they obtained with the DNA data of modern sheep and neolithic Central Asian sheep.
Eren Yüncü, the postdoctoral researcher at ODTÜ and one of the first authors of the study, said, "We knew that there are clear genetic differences between Asian sheep and European sheep in modern sheep breeds. During our analysis, it was surprising for us to see that these differences started at least 9,000 years ago."
"According to DNA results, today's European sheep are closely related to domestic sheep that lived in Central and Western Anatolia during the Neolithic period. But today's Asian sheep are different. Perhaps the ancestors of today's Asian sheep may have evolved in another region east of Anatolia. The region could be Iran, for example," he said.
Inci Togan, a retired faculty member who is the founder of the ODTÜ's Ancient DNA laboratory and one of the leaders of the study, said that domestication was possible in two regions during the Neolithic period. Togan said that previous ancient DNA studies with goats showed that goats were domesticated more than once in the west and east of the "Fertile Crescent," a crescent-shaped region in the Middle East, spanning modern-day Iraq, Syria, Lebanon, Palestine, Israel, Jordan, Egypt, together with the northern region of Kuwait, the southeastern region of Turkey and the western portion of Iran.
Stating that alternative scenarios were possible, Togan said, "Scenarios such as the rapid differentiation of sheep in the west and east after a single domestication or the mixing of wild sheep with domestic sheep in the east are still possible."
ODTÜ faculty member Mehmet Somel, one of the authors of the study, also emphasized that the history of sheep after domestication was a mixed bag.
"According to ancient DNA results, sheep underwent a lot of change in Europe and especially in Anatolia after domestication. The spread of breeds selected for their wool or oil may have played a role in this change," Somel said.