Origins of Domestic Sheep

Sheep were initially domesticated from the Asiatic mouflon (Ovis gmelini), which historically ranged from Turkey to eastern Iran. The earliest evidence of sheep management dates back to the mid-9th millennium BCE in the northern Fertile Crescent, a region known for its rich history of early animal husbandry. Archaeological records indicate shifts in species composition, diet, and bone pathologies, all of which suggest early human intervention in sheep breeding.

Early Neolithic sites in central Turkey, such as Aşıklı Höyük, provide some of the oldest genetic evidence of sheep domestication. However, genomic analyses indicate that these early populations do not entirely explain the ancestry of later domesticated sheep, suggesting a complex mosaic of wild and managed ancestries.

Dispersal of Domestic Sheep

The expansion of domesticated sheep populations across Eurasia followed human migration and trade routes. The first European flocks descended from Turkish sheep, migrating alongside early agricultural communities into Southeast Europe around 6,000 BCE. This movement mirrors patterns observed in ancient human genome studies, highlighting a broader relationship between early livestock and human dispersal.

One of the most significant genetic influxes occurred during the Bronze Age when a major migration from the Eurasian steppe introduced new genetic material into European sheep populations. This steppe-related ancestry reshaped domestic sheep populations, much like it influenced human populations across Europe during the same period. The genetic impact of this migration can be observed in modern European sheep breeds, which retain traces of this Bronze Age ancestry.

Selection for Key Traits

Ancient genomic studies provide insights into the selection pressures that shaped early sheep breeds. Herders selectively bred sheep for pigmentation patterns, hornedness, and growth rate, leading to gradual morphological and behavioral changes.

Pigmentation Patterns: Early domesticated sheep displayed a variety of coat colors, indicating that pigmentation was an important trait for early breeders. The genetic diversity in pigmentation genes suggests that herders selectively bred sheep for distinct fleece colors, potentially for religious, cultural, or practical reasons.

Hornedness: The presence or absence of horns has been a key trait in sheep domestication. Ancient genomic evidence suggests selective pressures influenced the development of both horned and polled (hornless) varieties, with variations persisting across different regions and time periods.

Growth Rate and Body Size: Domesticated sheep gradually decreased in size compared to their wild ancestors, a common pattern observed in many domesticated species. This reduction in size likely resulted from selective breeding for docility and manageability, as well as controlled feeding environments.

Wild Gene Influx and Hybridization

One of the most intriguing findings from ancient genomics is the evidence of ongoing gene flow between wild and domesticated sheep populations. Throughout prehistory, domestic sheep interbred with wild mouflon and other local wild sheep species, incorporating new genetic material that influenced their adaptation to different environments. This hybridization process contributed to the genetic diversity observed in modern sheep breeds.

In some regions, such as Iran and the Caucasus, genetic studies suggest that local wild sheep continued to contribute to domestic sheep gene pools for thousands of years. This continuous influx of wild genes likely provided adaptive advantages, allowing domestic sheep to thrive in diverse ecological conditions.

The Role of Wool in Early Societies

One of the most significant developments in sheep domestication was the emergence of woolly sheep. While early domestic sheep primarily provided meat and skins, genetic and archaeological evidence suggests that the selective breeding for wool production intensified during the 4th and 3rd millennia BCE in Southwest Asia. The ability to produce warm, breathable, and water-resistant textiles revolutionized early economies, contributing to the rise of complex societies.

By the Bronze Age, wool had become a major commodity, with evidence of large-scale wool production in Mesopotamian city-states. The spread of woolly sheep across Europe and Asia further supported the growth of textile industries, solidifying sheep's role in ancient economies.

The domestication and development of sheep were complex processes shaped by selective breeding, migration, and wild gene introgression. Ancient genomic research has provided unprecedented insights into these processes, revealing how early herders shaped sheep populations over millennia. The genetic legacy of these early domesticated sheep continues to influence modern breeds, highlighting the deep interconnection between human societies and their livestock.

As genomic technologies continue to advance, future research will likely uncover even more details about the origins and dispersal of domestic sheep, further enriching our understanding of human-animal interactions throughout history.

SOURCES: Ancient genomics and the origin, dispersal, and development of domestic sheep | Daly KG, Mullin VE, Hare AJ, Halpin Á, Mattiangeli V, Teasdale MD, Rossi C, Geiger S, Krebs S, Medugorac I, Sandoval-Castellanos E, Özbaşaran M, Duru G, Gülcür S, Pöllath N, Collins M, Frantz L, Vila E, Zidarov P, Stoddart S, Boldgiv B, Orlando L, Pearson MP, Mullville J, Askeyev IV, Askeyev AO, Askeyev OV, Shaymuratova DN, Van den Hurk Y, Zeeb-Lanz A, Arbogast RM, Hemmer H, Davoudi H, Amiri S, Doost SB, Decruyenaere D, Fathi H, Khazaeli R, Hassanzadeh Y, Sardari A, Lhuillier J, Abdolahi M, Summers GD, Marro C, Bahshaliyev V, Berthon R, Çakirlar C, Benecke N, Scheu A, Burger J, Sauer E, Horwitz LK, Arbuckle B, Buitenhuis H, Gourichon L, Bulatović J, O'Connor T, Orton D, Jalabadze M, Rhodes S, Chazan M, Özkaya V, Zeder M, Atıcı L, Mashkour M, Peters J, Bradley DG. Science. 2025 Jan 31;387(6733):492-497. doi: 10.1126/science.adn2094. Epub 2025 Jan 30. PMID: 39883774.