Rewriting the history of domestic animals in the shadow of the proto-Silk Road
New discoveries made through ancient DNA show that early animal domestication took root in the mountains of Central Asia more than 8000 years ago, nearly three millennia earlier than previously recognized.
A donkey laden with baggage accompanies a herd of sheep moving down a modern highway near Obishir, Kyrgyzstan.
Central Asia is a land of animals, and a land of social connections. For centuries, people in the high mountains of the continental interior have raised domestic livestock, relying on them for food, travel, trade, or war. Domestic animals carried the first travelers on the Silk Road, and supported great trans-Eurasian empires from the Persians to the Mongols and beyond. Today, domestic plants and animals are still the cornerstone of life and culture in the fertile valleys and high mountain pastures of the Tian Shan, Alay, and Pamir mountain ranges - a region researchers sometimes call the Inner Asia Mountain Corridor, or IAMC for short.
Because this region has always been a crossroads, those of us studying the history of people and animals in Central Asia are always looking for connections. The exchange and communication routes of the ancient world functioned like the spokes on a wagon wheel, with the mountains of Inner Asia at their center. But when did domestic animals first reach this part of the world, and from where? And what can these connections tell us about the world we live in today?
As archaeological science has advanced by leaps and bounds, its practitioners have made remarkable progress in answering these questions. Over the last decade scientists have reconstructed the spread of domestic crops westward from China, and eastwards from Mesopotamia, using careful screening and the study of tiny plant remains, an approach known as archaeobotany. But because the region's most ancient assemblages are often small and degraded, we've often had to do the archaeological equivalent of "reading the tea leaves" – working with data sets that are fragmentary, incomplete, or inconclusive. Now, emerging technologies are allowing us to overcome these challenges, and we are starting to unravel some unexpected secrets.
Archaeologist Saltanat Alisher-kyzy conducts new excavations at Obishir in 2017, a site originally explored by Soviet archaeologists in the 1970’s.
Among the first scholars to try to reconstruct the prehistory of humans and domestic animals in Central Asia were those of the Soviet era. With few of the tools we have today, these early researchers identified, excavated, and studied material culture from all across the continental interior. In reading the bones and stones they unearthed, some Soviet scholars envisioned an early adoption of domestic animals and domestic plants - a "Neolithic Revolution" that transformed early societies. Lacking in much direct evidence, though, the notion of an early Central Asian Neolithic failed to gain much traction among the broader interntational academic community.
A few years ago, my dear friend and coauthor Dr. Svetlana Shnaider (of the Institute of Archaeology and Ethnography at the Russian Academy of Sciences), came to me with a puzzle. With her research collaborator, Dr. Aida Abykanova of the American University of Central Asia, Svetlana had been doing research for years at an early Holocene rockshelter at the heart of this Inner Asia Mountain Corridor. The site was named by Soviet scholars as Obishir V, and is nestled in a mountainside along the southern edge of the Ferghana Valley: a wide basin straddling the modern nations of Kyrgyzstan, Uzbekistan, and Tajikistan. Dr. Shnaider told me: “I think we have evidence of domestic sheep and goat - thousands and thousands of years before they should be here.”
I was skeptical, especially given how small and fragmentary the assemblage from this rockshelter seemed to be. The animal bones she showed me - the results of years of painstaking excavations - filled only a few quart-sized Ziploc bags. Moreover, nearly every bone was broken into tiny slivers and splinters, likely due to how the animals had been processed and cooked thousands of years ago. But I was also intrigued: if Dr. Shnaider was right, such a finding could totally change how we think about the prehistory of Inner Asia.
Extracting collagen for ZooMS/fingerprinting at the Max Planck Institute for the Science of Human History.
We set to work trying to answer Svetlana's puzzle – but first we had to figure out a research plan. More standard kinds of zooarchaeological analyses, such as the anatomical comparisons we might usually perform to identify animal species, were of little value given the fragmented state of the assemblage. Partnering with Dr. Christina Warinner and Dr. Cosimo Posth at the Max Planck Institute for the Science of Human History, where Shnaider and I worked in 2017, we brainstormed other techniques that might give us answers. Previously, we had success using a mass spectrometry technique known as collagen fingerprinting to identify and understand small, fragmented assemblages linked to prehistoric animal economies in a nearby area of southern Kyrgyzstan. Trying this approach at Obishir showed us that nearly all of the unidentifiable bones belonged to sheep or goat - but the results couldn't allow distinguish between domestic animals or their wild relatives. Follow-up analyses of the site's sheep and goat teeth by a specialist, Dr. William Rendu, suggested that the animals all died in the fall, a pattern consistent with the seasonal culling practices of some herders. We were excited - but we needed something more concrete. Finally, we decided to dive into ancient DNA, working with Drs. Warinner and Posth, along with Dr. Melanie Pruvost at the University of Bordeaux, to sequence genomic material from the sheep and goats from Obishir, and compare them to reference genomes from wild and domestic animals.
When our first results came back, we were stunned. Dr. Shnaider’s hunch was right – these were domestic animals! Domestic sheep and goat, thousands of kilometers east of Mesopotamia, and thousands of years before we expected them. Direct radiocarbon dating of these sheep showed us that the assemblage dated to more than 8,000 years ago, ca. 6000 BCE, and reconstructed genome-wide DNA sequences showed that Obishir sheep fell within the variation of domesticated sheep breeds, and that they belonged to mitochondrial haplogroup A, one of the oldest haplogroups for domestic sheep seen in the Near East. This means that while the first herders and farmers were reshaping the natural and cultural landscapes of Europe, northern Africa, and South Asia, herding lifeways were also taking root in the shadow of what would later become the Silk Roads.
Artist reconstruction of early herder with domestic sheep and goats at Obishir, ca. 6000 BCE. Illustration: Ettore Mazza
Our international team will spend the coming years figuring out precisely what these findings mean for Eurasia's past. Did these ancient herders in the IAMC move there from Mesopotamia? Or were the animals exchanged and passed to ancient Central Asians indirectly, through trade? Did domestic plants, like wheat and barley, or other domestic animals, like cattle, also make the journey? How far did domesticates move into Asia beyond Obishir – did people bring them further into the Pamir, Karakorum, Kunlun, or Himalaya to the south, Tian Shan and Kunlun mountains to the east, or the Altai Mountains to the north? Did these first pastoral economies in the mountains of Central Asia provide a staging area for their later movement into places like Mongolia or China? How did the introduction of domestic animals impact the social structure, religious beliefs, or landscapes of ancient Central Asia?
Because the spread of domestic animals throughout Eurasia – for food, fiber, and transportation - have contributed so much to the roots of our modern, globalized world, answering these questions will be essential to understanding our collective past and our collective future. By continuing to make the most of emerging technologies with international scientific teams that can navigate Eurasia's many linguistic and political boundaries, archaeological science will rewrite the “prehistory books” for this crucial region of the ancient world.
See the associated study, "Evidence for early dispersal of domestic sheep into Central Asia" in Nature: Human Behavior here.