Ancient DNA analyses bring to life the 11,000-year intertwined genomic history of sheep and humans

Sheep have been intertwined with human livelihoods for over 11,000 years. As well as meat, their domestication led to humans being nourished by their protein-rich milk and clothed by warm, water-resistant fabrics made from their wool. 

Now, an international and interdisciplinary team of researchers led by geneticists from Trinity College Dublin and zooarchaeologists from LMU Munich and the Bavarian State Collections of Natural History (SNSB) has deciphered the prehistoric cultural trajectory of this species by analysing 118 genomes recovered from archaeological bones dating across 12 millennia and stretching from Mongolia to Ireland. 

The earliest sheep-herding village in the sample, Aşıklı Höyük in central Türkiye, has genomes that seem ancestral to later populations in the wider region, confirming an origin in captures of wild mouflon over 11,000 years ago in the western part of the northern Fertile Crescent.

By 8,000 years ago, in the earliest European sheep populations, the team found evidence that farmers were deliberately selecting their flocks – in particular for the genes coding for coat colour.  Along with a similar signal in goats, this is the earliest evidence for human moulding of another animal’s biology and shows that early herders, like today’s farmers, were interested in the beautiful and unusual in their animals.

Specifically, the main gene the team found evidence of selection near was one known as “KIT”, which is associated with white coat colour in a range of livestock.

Also by that time, the earliest domestic sheep genomes from Europe and further east in Iran and Central Asia had diverged from each other. However, this separation did not last as people translocated sheep from eastern populations to the west.  

First, in parallel with human cultural influences spreading out from the early cities of Mesopotamia we see sheep genomes moving west within the Fertile Crescent around 7,000 years ago.

Second, the rise of pastoralist peoples in the Eurasian steppes and their westward spread some 5,000 years ago profoundly transformed ancestral European human populations and their culture. This process changed the makeup of human populations, for example, altering the ancestry of British peoples by around 90%, and introduced the Indo-European language ancestor of the tongues spoken across the continent today.

From the dataset used in this study it now seems that this massive migration was fuelled by sheep herding and exploitation of lifetime products, including milk and probably cheese, as it is around the same time that sheep ancestries are also changed. Consequently, by the Bronze Age, herds had about half their ancestry from a source in the Eurasian steppe.

Dr Kevin Daly, Ad Astra Assistant Professor at UCD School of Agriculture and Food Science and an Adjunct Assistant Professor in Trinity’s School of Genetics and Microbiology, is the first author on the research article that has just been published in leading international journal Science. He said: “One of our most striking discoveries was a major prehistoric sheep migration from the Eurasian steppes into Europe during the Bronze Age. This parallels what we know about human migrations during the same period, suggesting that when people moved, they brought their flocks with them.”

Dan Bradley, leader of the research and Professor of Population Genetics in Trinity’s School of Genetics and Microbiology, said: “This research demonstrates how the relationship between humans and sheep has evolved over millennia. From the early days of domestication through to the development of wool as a crucial textile resource, sheep have played a vital role in human cultural and economic development.”

Joris Peters, co-corresponding author, Professor of Paleoanatomy, Domestication Research and the History of Veterinary Medicine at LMU Munich and Director of the State Collection for Paleoanatomy Munich (SNSB-SPM), said: “Our study, while convincingly reconciling morphological and genomic evidence of the geographic origin of domestic sheep, clearly illustrates that further transdisciplinary research is needed to clarify the patterns of dispersal and selection of the many landraces occurring today in Eurasia and Africa.”

END