Endogenous Retroviral Insertions Indicate a Secondary Introduction of Domestic Sheep Lineages to the Caucasus and Central Asia between the Bronze and Iron Age

Abstract

Sheep were one of the first livestock species domesticated by humans. After initial domestication in the Middle East they were spread across Eurasia. The modern distribution of endogenous Jaagsiekte sheep retrovirus insertions in domestic sheep breeds suggests that over the course of millennia, successive introductions of improved lineages and selection for wool quality occurred in the Mediterranean region and most of Asia. Here we present a novel ancient DNA approach using data of endogenous retroviral insertions in Bronze and Iron Age domestic sheep from the Caucasus and Pamir mountain areas. Our findings support a secondary introduction of wool sheep from the Middle East between the Late Bronze Age and Iron Age into most areas of Eurasia.

Retroviral analysis reveals the ancient origin of Kihnu native sheep in Estonia: implications for breed conservation

“…A local selection that favoured enJSRV-18 and wool quality is also a possibility. However, as Schroeder et al 20 have discussed, local selection would not explain why this retrovirus became widespread "in almost all modern breeds of Eurasia since the retroviral insertions are … not causally linked with improved wool production". www.nature.com/scientificreports/ The frequency of enJS5F16 has been quite constant from the Iron Age to Modern Period (in average 46%) and decreased to 36% in the Kihnu sheep.…”

“…A local selection that favoured enJSRV-18 and wool quality is also a possibility. However, as Schroeder et al 20 have discussed, local selection would not explain why this retrovirus became widespread “in almost all modern breeds of Eurasia since the retroviral insertions are … not causally linked with improved wool production”.…”

“…For the last decade, other scholars have used the same approach using enJSRVs in phylogeographic and population genetics studies, mainly to identify and preserve primitive breeds with rare gene pools [14][15][16][17][18][19] . Recently, first attempts have been made to apply this method to ancient sheep samples 20 .…”

Mitochondrial DNA analysis of ancient sheep from Kazakhstan: evidence for early sheep introduction

“…The first possible source of domestic sheep introduction is the pre-Caspian Caucasus region, which is considered to be among the primary localities for sheep breeding after the Fertile Crescent [ 3 ]. An early introduction of sheep from the Pontic-Caspian steppe to western Kazakhstan by Afanasevo culture is likely [ 33 ].…”

“…The history of domestic sheep began in the Fertile Crescent around 11,000 BP [ 1 ]. Subsequently, sheep were introduced to Eurasia through several routes that bypass the Caspian Sea [ 2 , 3 , 4 ]. During this period, 5,000–7,000 years ago, Central Asia played a significant role in the “transport interchange” of migratory flows [ 2 , 3 ].…”