Origin of domestic horses finally established

Origin of domestic horses finally established

origin domestic horses domestic horse
Origin of domestic horses finally established. Farmer catching horses in north-central Kazakhstan. © Ludovic ORLANDO / CAGT / CNRS Photothèque

Horses were first domesticated in the Pontic-Caspian steppes, northern Caucasus, before conquering the rest of Eurasia within a few centuries. These are the results of a study led by paleogeneticist Ludovic Orlando, CNRS, who headed an international team including l’Université Toulouse III - Paul Sabatier, the CEA and l’Université d’Évry. Answering a decades-old enigma, the study is published in Nature on 20 October 2021.

By whom and where were modern horses first domesticated? When did they conquer the rest of the world? And how did they supplant the myriad of other types of horses that existed at that time? This long-standing archaeological mystery finally comes to an end thanks to a team of 162 scientists specialising in archaeology, palaeogenetics and linguistics.

A few years ago, Ludovic Orlando's team looked at the site of Botai, Central Asia, which had provided the oldest archaeological evidence of domestic horses. The DNA results, however, were not compliant: these 5500-year-old horses were not the ancestors of modern domestic horses1. Besides the steppes of Central Asia, all other presumed foci of domestication, such as Anatolia, Siberia and the Iberian Peninsula, had turned out to be false.

We knew that the time period between 4,000 to 6,000 years ago was critical but no smoking guns could ever be found” says CNRS research professor Orlando.

The scientific team, therefore, decided to extend their study to the whole of Eurasia by analysing the genomes of 273 horses that lived between 50,000 and 200 years BC. This information was sequenced at the Centre for Anthropobiology and Genomics of Toulouse (CNRS/Université Toulouse III - Paul Sabatier) and Genoscope2 (CNRS/CEA/Université d’Évry) before being compared with the genomes of modern domestic horses.

This strategy paid off: although Eurasia was once populated by genetically distinct horse populations, a dramatic change had occurred between 2000 and 2200 BC.

That was a chance: the horses living in Anatolia, Europe, Central Asia and Siberia used to be genetically quite distinct” notes Dr Pablo Librado, first author of the study.

Then, a single genetic profile, previously confined to the Pontic steppes (North Caucasus)3, began to spread beyond its native region, replacing all the wild horse populations from the Atlantic to Mongolia within a few centuries.

The genetic data also point to an explosive demography at the time, with no equivalent in the last 100,000 years” adds Orlando. “This is when we took control over the reproduction of the animal and produced them in astronomic numbers.”

But how can this rapid population growth be explained? Interestingly, scientists found two striking differences between the genome of this horse and those of the populations it replaced: one is linked to a more docile behaviour and the second indicates a stronger backbone. The researchers suggest that these characteristics ensured the animals’ success at a time when horse travel was becoming “global”.

The study also reveals that the horse spread throughout Asia at the same time as spoke-wheeled chariots and Indo-Iranian languages. However, the migrations of Indo-European populations, from the steppes to Europe during the third millennium BC4 could not have been based on the horse, as its domestication and diffusion came later. This demonstrates the importance of incorporating the history of animals when studying human migrations and encounters between cultures.

origine cheval
Origin of domestic horses finally established. Horse mandible excavated from the Ginnerup archaeological site, Denmark, June 2021. (This site was included in the study.) © Lutz Klassen, East Jutland Museum

This study was directed by the the Centre for Anthropobiology and Genomics of Toulouse (CNRS/ Université Toulouse III – Paul Sabatier) with help from Genoscope (CNRS/CEA/Université d’Évry). The French laboratories Archéologies et sciences de l'Antiquité (CNRS/Université Paris 1 Panthéon Sorbonne/Université Paris Nanterre/Ministère de la Culture), De la Préhistoire à l'actuel: culture, environnement et anthropologie (CNRS/Université de Bordeaux/Ministère de la Culture) and Archéozoologie, archéobotanique : sociétés, pratiques et environnements (CNRS/MNHN) also contributed, as did 114 other research institutions throughout the world. The study was primarily funded by the European Research Council (Pegasus project) and France Genomique (Bucéphale project).

Some previous results of the Pegasus project:

Notes

1 Read this press release: Unsaddling old theory on origin of horses, 22 February 2018.
2 Genoscope is a department of CEA-Jacob.
3 The Pontic steppe is the western part of the Eurasian steppe. The home of the modern domestic horse is thought to be in the Don and Volga basins, east of the Dnieper.
4 For example, see this press release: 7,000 years of demographic history in France, 25 May 2020.

 

Press release from CNRS on the study, published on Nature, concerning the origin of domestic horses.

The new study on the origin of domestic horses, references:

Librado, P., (...), Orlando, Ludovic (2021). "The origins and spread of domestic horses from the Western Eurasian steppes". Nature, 20/10/2021. DOI: 10.1038/s41586-021-04018-9

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Horses were domesticated in the Northern Caucasus steppes and then spread across Asia and Europe

 

A large group of researchers have conducted the largest genetic study carried out to date, which has made it possible to determine that the horses from which all current domestic horses descend were first domesticated in the steppes north of the Caucasus and, from there, spread to other regions of Asia and Europe.

Researchers from the Milá y Fontanals Institution (IMF) and the Institute of Archaeology (IAM) of the Spanish National Research Council (CSIC), together with scientists from the Museum of Human Evolution (MEH), the Faculty of Veterinary Medicine of the University of Extremadura (UEx), the UCM-ISCIII Joint Centre for Human Evolution and Behaviour in Madrid, the Laboratory of Prehistoric Archaeology of the University Jaume I of Castellón (UJI) and the Faculty of Geological Sciences of the Complutense University of Madrid (UCM)have participated in the largest genetic study carried out to date, which has made it possible to determine that the horses from which all current domestic horses descend were first domesticated in the steppes north of the Caucasus and, from there, spread to other regions of Asia and Europe.

This study brings to an end a long-standing debate about the location and chronology of the earliest documented evidence of domestication of the horses that gave rise to today's populations, as well as aswering questions about when this domestication process began to spread to other regions of the world, thus replacing other types of horses that existed at the time. The results have been published in the October issue of prestigious international journal Nature.

This conclusion was reached by a team of 114 institutions and 162 researchers specialising in archaeology, palaeogenetics and linguistics, led by Professor Ludovic Orlando, CNRS researcher and principal investigator of the ERC-PEGASUS project, which, together with France Genomique-Projet Bucéphale, financed the research. The study involved sequencing the genomes of 273 remains of horses that inhabited various regions of Eurasia in a chronological arc extending from 50,000 to 200 BC. All the genetic information was sequenced at the Centre for Anthropobiology and Genomics of Toulouse, CAGT (CNRS/University of Toulouse III-Paul Sabatier) and Genoscope (CNRS/CEA/University of Évry), before being compared to the genomes of modern domestic horses. Thanks to the large battery of statistical analyses carried out, it has been possible to establish that between 2,200 and 2,000 BC, a drastic change took place in which the genetic profile existing in the Pontic steppes began to spread beyond its region of origin, thus replacing in a few centuries all wild horse populations from the Atlantic to Mongolia.

According to L. Orlando, "this replacement in the genetic composition of Eurasian populations is associated with significant genomic differences between this new type of horse and the horses of the populations that disappeared. On the one hand, this new type of horse from the steppes of the northern Caucasus had a more docile behaviour and, on the other hand, a more robust constitution in the vertebral skeleton".

The researchers suggest that these characteristics triggered the successful selection of these animals, at a time when horse travel was becoming widespread in Eurasia.

According to Pablo Librado (CNRS), first author of this research, "this study has also shown that the distribution of this new type of horse in Asia coincides with the appearance of light carts and the spread of Indo-Iranian languages. In contrast, the migration of Indo-European populations from the steppe zone to the heart of Europe during the third millennium BC did not use this new type of horse as a vector for its expansion. This result demonstrates the importance of also incorporating the genetic history of animals when analysing the dimension of human migrations and intercultural contacts".

The individuals analysed include equids from various sites on the Iberian Peninsula, including Casas del Turuñuelo (Guareña, Badajoz) and Cova Fosca (Alt Maestrat, Castelló).

The Cova Fosca was excavated by Francesc Gusi and Carmen Olaria. According to C. Olaria, professor of Prehistory at the UJI and co-author of this study,

"Cova Fosca has a very rich Holocene archaeozoological record. We were able to identify horse remains in ancient Neolithic levels, a very rare taxon in Iberian sites from this period. This uniqueness allowed us to publish years ago, together with Jaime Lira Garrido and Juan Luis Arsuaga, the first mitochondrial sequences of horses from this site".

According to J. L. Arsuaga, scientific director of the Museum of Human Evolution, professor of Palaeontology at the UCM, director of the UCM-ISCIII Joint Centre and co-author of this study,

"in Cova Fosca we found a unique mitochondrial lineage exclusive to Iberia that currently appears in very few horses, all of which are Iberian or of Iberian origin. In this new study we aimed to unveil the genomic secrets of the Cova Fosca".

Building Tartessos and Casas del Turuñuelo

origin domestic horses horse
A new study on the origin of domestic horses.View of animal slaughter documented in the courtyard of the building at Casas del Turuñuelo

Casas del Turuñuelo is one of the most impressive discoveries in peninsular archaeology in recent years. Its excavations are being carried out under a project directed by the IAM-CSIC and are being co-directed by Esther Rodríguez González and Sebastián Celestino, also researchers at the IAM-CSIC.

According to Esther Rodríguez González, co-author of this new study, "Turuñuelo is an architectural complex from the middle of the first millennium BC belonging to the Tartessos culture where we have found the largest hecatomb documented to date in a site of Mediterranean protohistory. This mass slaughter is notable for the large number of equids that have been differentiated in the courtyard of this site. For this study we selected Equid 4".According to Sebastián Celestino, also co-author of this research, "a multidisciplinary team of specialists from the humanities and biosciences has been created around Turuñuelo, which is generating a constant exchange of information and ideas, thus offering a great multidisciplinary approach to the study of this site".

Among the lines of research of "Construyendo Tartessos" [Building Tartessos], the genetic study of these slaughtered equids stands out. Jaime Lira Garrido (UEx/Centro Mixto UCM-ISCIII), who is a co-author of this study, explains that

"this latest work led by Professor Orlando has also allowed us to delve deeper into the evolutionary history of Iberian horses. In a previous study, Orlando and his team discovered that a genomic lineage developed on the Iberian Peninsula that is now extinct and very different from the rest of the ancient and modern Eurasian horse lineages described to date. The evolutionary origin of this lineage and the causes that led to its disappearance are still unknown. However, we have been able to identify in the Neolithic sample from the Cova Fosca the oldest evidence of this extinct lineage and that the Turuñuelo Equid 4 was, nevertheless, a descendant of this new type of horse that was so rapidly distributed throughout the known world some 4.000 years ago".

This study has been funded mainly by the European Research Council (PEGASUS project) and France Genomique (Bucéphale project).

 

Press release from Asociación RUVID on the new study on the origin of domestic horses.

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South Ural State University (SUSU) scientists and their foreign colleagues have continued study devoted to the time and place of horse domestication. A research group has established where exactly the focus of domestication is located in Eurasia. The results of the work have been published in the highly rated journal “Nature” (Top 10%).

The identical signs have been found in the genomes of domesticated horses in Eurasia. Specialists have noticed that remains of these animals have a strong spine. Probably, this is the reason for domesticated horses popularity and global spreading of horse travels.

The research group which includes PhD, SUSU professor Andrey Epimakhov has established the Pontic-Caspian steppes, northern Caucasus, is the centre of horse domestication. The process has occurred between 2000 and 2200 BC (the Bronze Age). Horses are distinct i n different presumed foci of domestication such as Anatolia, Siberia and the Iberian Peninsula, but several ages later the common genome has spreaded from the Atlantic to Mongolia within a few centuries.

Our research group that is led by paleo-geneticist Ludovic Orlando, National Center for Scientific Research (France), has analysed the genomes of 273 horses that lived between 50,000 and 200 years BC. The study has covered the whole of Eurasia to research presumed territories to be considered as primary foci of domestication. However, all of the territories have turned out to be false. For instance, the site of Botai, Central Asia, has provided the oldest archaeological evidence of domestic horses. Nevertheless, the DNA results are not compliant: these 5500-year-old horses are not the ancestors of modern domestic horses. On the contrary, the Ural 4000 years old samples don’t raise doubts in horse exploitation and chariot teams,” Andrey Epimakhov explained.

Research has also demonstrated that the horse spread throughout Asia at the same time as spoke-wheeled chariots and Indo-Iranian languages.

Remind that dental calculus research has helped scientists to determine the time and place of horse domestication. There are dairy diet markers that have been detected in samples found in the Volga region. Milk has been a part of people's ration since animal domestication.

 

Press release from the South Ural State University on the new study on the origin of domestic horses.


Bone circles made from the remains of mammoths reveal clues about Ice Age

Mysterious bone circles made from the remains of mammoths reveal clues about Ice Age

Mysterious bone circles made from the remains of dozens of mammoths have revealed clues about how ancient communities survived Europe's ice age.

About 70 of these structures are known to exist in Ukraine and the west Russian Plain.

The majority of the bones found at the site investigated, in the Russian Plains, are from mammoths. A total of 51 lower jaws and 64 individual mammoth skulls were used to construct the walls of the 30ft by 30ft structure and scattered across its interior Credits: Alex Pryor

New analysis shows the bones at one site are more than 20,000 years old, making it the oldest such circular structure built by humans discovered in the region. The bones were likely sourced from animal graveyards, and the circle was then hidden by sediment and is now a foot below current surface level.

The majority of the bones found at the site investigated, in the Russian Plains, are from mammoths. A total of 51 lower jaws and 64 individual mammoth skulls were used to construct the walls of the 30ft by 30ft structure and scattered across its interior. Small numbers of reindeer, horse, bear, wolf, red fox and arctic fox bones were also found.

bone cicles mammoths
Credits: Alex Pryor

Archaeologists from the University of Exeter have also found for the first time the remains of charred wood and other soft non-woody plant remains within the circular structure, situated just outside the modern village of Kostenki, about 500km south of Moscow. This shows people were burning wood as well as bones for fuel, and the communities who lived there had learned where to forage for edible plants during the Ice Age. The plants could also have been used for poisons, medicines, string or fabric. More than 50 small charred seeds were also found - the remains of plants growing locally or possibly food remains from cooking and eating.Dr Alexander Pryor, who led the study, said: "Kostenki 11 represents a rare example of Palaeolithic hunter-gatherers living on in this harsh environment. What might have brought ancient hunter gatherers to this site? One possibility is that the mammoths and humans could have come to the area on masse because it had a natural spring that would have provided unfrozen liquid water throughout the winter - rare in this period of extreme cold.

"These finds shed new light on the purpose of these mysterious sites. Archaeology is showing us more about how our ancestors survived in this desperately cold and hostile environment at the climax of the last ice age. Most other places at similar latitudes in Europe had been abandoned by this time, but these groups had managed to adapt to find food, shelter and water."

bone cicles mammoths
Credits: Alex Pryor

The last ice age, which swept northern Europe between 75-18,000 years ago, reached its coldest and most severe stage at around 23-18,000 years ago, just as the site at Kostenki 11 was being built. Climate reconstructions indicate at the time summers were short and cool and winters were long and cold, with temperatures around -20 degrees Celsius or colder. Most communities left the region, likely because of lack of prey to hunt and plant resources they depended upon for survival. Eventually the bone circles were also abandoned as the climate continued to get colder and more inhospitable.

Previously archaeologists have assumed that the circular mammoth bone structures were used as dwellings, occupied for many months at a time. The new study suggests this may not always have been the case as the intensity of activity at Kostenki 11 appears less than would be expected from a long term base camp site.

Other finds include more than 300 tiny stone and flint chips just a few millimetres in size, debris left behind the site's inhabitants as they knapped stone nodules into sharp tools with distinctive shapes used for tasks such as butchering animals and scraping hides.

The research, conducted by academics from the University of Exeter, University of Cambridge, Kostenki State Museum Preserve, University of Colorado Boulder and the University of Southampton, is published in the journal Antiquity.

 

Press release "Mysterious bone circles made from the remains of mammoths reveal clues about Ice Age" from the University of Exeter.


5,000-year-old milk proteins point to the importance of dairying in eastern Eurasia

5,000-year-old milk proteins point to the importance of dairying in eastern Eurasia

Recent findings push back estimates of dairying in the eastern Steppe by more than 1,700 years, pointing to migration as a potential means of introduction

 

Today dairy foods sustain and support millions around the world, including in Mongolia, where dairy foods make up to 50% of calories consumed during the summer. Although dairy-based pastoralism has been an essential part of life and culture in the eastern Eurasian Steppe for millennia, the eastward spread of dairying from its origin in southwest Asia and the development of these practices is little understood. The current study, led by Shevan Wilkin and Jessica Hendy of the Max Planck Institute for the Science of Human History, presents the earliest evidence for dairy consumption in East Asia, circa 3000 BCE, and offers insights into the arrival and evolution of dairy pastoralism in prehistoric Mongolia.

dairying Eurasia
These are horses on the steppe. Credits: Björn Reichhardt

Earliest dairy consumption & a possible path of entry

The highly mobile nature of pastoralist societies and the severe winds of the Eastern Steppe make detecting occupied sites with direct evidence into the lives and culture of ancient Mongolians exceedingly rare. Instead, the researchers looked for clues in ritual human burial mounds, often marked by stone monuments and occasionally featuring satellite animal graves.

In collaboration with the National University of Mongolia, researchers analyzed dental calculus from individuals ranging from the Early Bronze Age to the Mongol Period. Three-quarters of all individuals contained evidence that they had consumed dairy foods, which demonstrates the widespread importance of this food source in both prehistoric and historic Mongolia. The study's results include the earliest direct evidence for dairy consumption in East Asia, identified in an individual from the Afanasievo site of Shatar Chuluu, which dates to roughly 3000 BCE. Previous DNA analysis on this individual revealed non-local genetic markers consistent with Western Steppe Herder populations, presenting Early Bronze Age Afanasievo migrations westward via the Russian Altai as a viable candidate for the introduction of dairy and domestic livestock into eastern Eurasia.

Multiple different animal species were used for their milk

dairying Eurasia
These are sheep and goat herds in Mongolia. Credits: Björn Reichhardt

By sequencing the milk proteins extracted from the dental calculus, the scientists were able to determine which animal species were being used for dairy production, and thereby help to trace the progression of domestication, dairying, and pastoralism in the region. "Modern Mongolians use cow, sheep, goat, yak, camel, horse and reindeer for milk today, yet when each of these species were first utilized for dairy in Mongolia remains unclear," says Shevan Wilkin, lead author of the study. "What is clear is that the crucial renewable calories and hydration made available through the incorporation of dairying would have become essential across the arid and agriculturally challenging ancient Eastern Steppe."

The earliest individuals to show evidence of dairy consumption lived around 5000 years ago and consumed milk from ruminant species, such as cattle, sheep, and goats. A few thousand years later, at Bronze Age sites dated to after 1200 BCE, the researchers find the first evidence of horse milk consumption, occurring at the same time as early evidence for horse bridling and riding, as well as the use of horses at ritual burial sites. In addition, the study shows that during the Mongol Empire circa 1200-1400 CE, people also consumed the milk of camels. "We are excited that through the analysis of proteins we are able to see the consumption of multiple different animal species, even sometimes in the same individual. This gives us a whole new insight into ancient dairying practices" says Jessica Hendy, senior author of the study.

Millenia after the first evidence of horse milk consumption, horses remain vital to the daily lives of many in modern Mongolia, where mounted pastoralists rely on them to manage large herds of livestock, transport people and supplies, and provide a primary source of meat and milk. "Our findings suggest that the incorporation of horses into dairy pastoralism in Eastern Eurasia was closely linked to a broader economic transformation in the use of horses for riding, movement, and diet," says William Taylor of the University of Colorado-Boulder, one of the study's coauthors.

Although the earliest individual sampled in this study showed evidence of dairy consumption, the researchers hope future studies will examine individuals from previous time periods. "In order to form a clearer picture of the origins of dairying in this region, we need to understand the impact of western steppe herder migrations and confirm whether dairying was occurring in Mongolia prior to their arrival," Shevan Wilkin concludes.

dairying Eurasia
This is a horse burial at Morin Mort, Mongolia. Credits: William Taylor

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Publication information:

Title: Dairy pastoralism sustained Eastern Eurasian steppe populations for 5000 years

Authors: Shevan Wilkin, Alicia Ventresca Miller, William T.T. Taylor, Bryan K. Miller, Richard W. Hagan, Madeleine Bleasdale, Ashley Scott, Sumiya Gankhuyg, Abigail Ramsoe, S. Uliziibayar, Christian Trachsel, Paolo Nanni, Jonas Grossmann, Ludovic Orlando, Mark Horton, Philipp W. Stockhammer, Erdene Myagmar, Nicole Boivin, Christina Warinner, Jessica Hendy

Publication: Nature Ecology & Evolution

DOI: 10.1038/s41559-020-1120-y

 

Press release from the Max Planck Institute for the Science of Human History / DE


horse genetic history

A genomic tour-de-force reveals the last 5,000 years of horse history

A genomic tour-de-force reveals the last 5,000 years of horse history

horse genetic history
This image shows a herd of Kazakh horses in the Pavlodar region of Kazakhstan in August 2016. Credit: Ludovic Orlando

Each year on the first Saturday in May, Thoroughbred horses reach speeds of over 40 miles per hour as they compete to win the Kentucky Derby. But the domestic horse wasn't always bred for speed. In fact, an international team now has evidence to suggest that the modern horse is genetically quite different from the horses of even just a few hundred years ago.

Their work, appearing May 2 in the journal Cell, constructs the genetic history of the domestic horse across the world over the last 5,000 years by using the largest genome collection ever generated for a non-human organism. The findings identify two new horse lineages that are now extinct and suggest that familiar traits such as speed were only selected for more recently in their history.

"The horse has impacted human history like no other animal," says Ludovic Orlando (@LudovicLorlando), a research director with CNRS and the University of Toulouse and a Professor of Molecular Archaeology at the University of Copenhagen. "If you look at the historical record from the Bronze Age onward, horses are always part of the equation up until very recent times, connecting civilizations and impacting transportation, warfare, and agriculture. Our goal was to understand how humans and their activities transformed the horse throughout history to fit their purposes--and how these changes in biology influenced human history."

The team responsible for this project consisted of 121 collaborators, including geneticists, archaeologists, and evolutionary biologists from 85 institutions around the world, and examined genome-scale data from 278 horse specimens from across Eurasia over the last 42,000 years.

"Such a large collection of data means that we can build a much more precise understanding of horse domestication and management through space and time," Orlando says. "But it was truly an interdisciplinary effort because of course it takes a lot more than just DNA to understand such a story. We had to integrate all these social, historical, and geographical aspects."

This graphical abstract summarizes horse genetic history over the last 5,000 years. Credit: Fages et al./Cell

Overall, the team's findings suggest that equine history was much more complex than was previously realized. Today, there are only two known lineages of horses, the domestic horse and the Przewalski's horse. But the researchers here identified two additional now-extinct lineages of horses, one from the Iberian Peninsula and one from Siberia, both of which still existed 4,000-4,500 years ago. "We found two lineages of horses at the far ends of Eurasia that are not related to what we call the domestic horse today, nor to the Przewalski's horse. They are a sort of horse equivalent of what Neanderthals are to modern humans," Orlando says.

The researchers also found a major shift in the genetic makeup of horses in Europe and Central Asia in the 7th to 9th centuries and say this shift probably corresponds to Islamic expansions. The horses common in Europe before that time are now only found in regions such as Iceland; the new European horses after that time were much more similar to horses found in Persia during the Sassanid Empire. When the team performed a scan to identify genes that had been selected for in these Persian horses, they found evidence of selection in genes associated with body shape.

"It was a moment in history that reshaped the landscape of horses in Europe. If you look at what we today call Arabian horses, you know that they have a different shape--and we know how popular this anatomy has been throughout history, including in racing horses. Based on the genomic evidence, we propose that this horse was so successful and influential because it brought a new anatomy and perhaps other favorable traits," he says.

The researchers found that there have been additional significant and recent changes in the domestic horse. Similar selection scans indicate that only in the last 1,500 years did traits such as ambling and speed over short distances become more actively sought. And when they looked at the overall genetic diversity of the domestic horse, the researchers found a sharp decline in the last 200 to 300 years. They believe this decline corresponds with new breeding practices that were introduced with the rise of the concept of "pure" breeds.

"What we picture as a horse today and what we picture as a horse from a thousand years ago or two thousand years ago was likely actually very different. Some of those traits that we are most familiar with are only a modern invention, and in the last few hundred years, we have actually impacted the horse genome a lot more than in the previous 4,000 years of domestication," says Orlando.

This map shows the locations of the archaeological sites where horse remains were found. Credit: Fages et al./Cell

He believes that this research can tell us a lot about both the past and the present. "Our findings show that the past is a lot more diverse than we thought it was and that it cannot be imagined or inferred through modern-day variation. But ancient DNA tells us a lot about today as well, because it teaches us about the consequences of some shifts in breeding practices," he says. And that, he believes, can also affect the way we think about conservation and modern agricultural practices.

Of course, our understanding of the domestic horse's history is far from complete. Orlando acknowledges that there are geographic and temporal gaps in his story. Perhaps mostly glaringly, we still don't know when and or where the horse was domesticated. "Horse domestication is central to human history, and in 2019, we still don't understand where it started. That's mind-blowing," he says.

He looks forward to filling in those blanks. "Whenever I'm asked about what finding I'm most excited about, I always say, the next one. Because this research opens the door for so many possibilities to be studied now."

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Inner Eurasia

Details of the history of inner Eurasia revealed by new study

Details of the history of inner Eurasia revealed by new study

Researchers combining genetics, archaeology, history and linguistics have gained new insights into the history of inner Eurasia, once a cultural and genetic crossroads connecting Europe and Asia

Inner Eurasia
Children from one of the Tajikistan communities included in the study. Credit: Elena Balanovska

An international team of researchers has combined archaeological, historical and linguistic data with genetic information from over 700 newly analyzed individuals to construct a more detailed picture of the history of inner Eurasia than ever before available. In a study published in Nature Ecology & Evolution, they found that the indigenous populations of inner Eurasia are very diverse in their genes, culture and languages, but divide into three groups that stretch across the area in east-west geographic bands.

Inner Eurasia, including areas of modern-day Armenia, Georgia, Kazakhstan, Moldova, Mongolia, Russia, Tajikistan, Ukraine and Uzbekistan, was once the cross-roads connecting Asia and Europe, and a major intersection for the exchange of culture, trade goods and genes in prehistory and historical periods, including the era of the famous Silk Road.

This vast area can also be divided into several distinct ecological regions that stretch in largely east-west bands across Inner Eurasia, consisting of the deserts at the southern edge of the region, the steppe in the central part, taiga forests further north, and tundra towards the Arctic region. The subsistence strategies used by indigenous groups in these regions largely correlate with the ecological zones, for example reindeer herding and hunting in the tundra region and nomadic pastoralism on the steppe.

Despite the long and important history of inner Eurasia, details about past migrations and interactions between groups are not always clear, especially in prehistory. "Inner Eurasia is a perfect place to investigate the relationship between environmental conditions and the pattern of human migration and mixture, as well as changes driven by cultural innovations such as the introduction of dairy pastoralism into the steppe," states Choongwon Jeong of the Max Planck Institute for the Science of Human History, co-first and senior author of the paper. In order to clarify our understanding of some of the nuances of the history of the region, an international team of researchers undertook an ambitious project to use modern and ancient DNA from a broad geographic range and time period, in concert with archaeological, linguistic and historical information, to clarify the relationships between the different populations. "A few ethnic groups were studied previously," comments Oleg Balanovsky from the Vavilov Institute of General Genetics in Moscow, also co-first author, "but we conducted more than a hundred field trips to study this vast region systematically, and reached communities speaking almost all of the Inner Eurasian languages".

Three distinct east-west groupings

For this study, the researchers analyzed DNA from 763 individuals from across the region as well as reanalyzed the genome-wide data from two ancient individuals from the Botai culture, and compared those results with previously published data from modern and ancient individuals. They found three distinct genetic groupings, which geographically are arranged in east-west bands stretching across the region and correlating generally to ecological zones, where populations within each band share a distinct combination of ancestries in varying proportions.

The northernmost grouping, which they term "forest-tundra", includes Russians, all Uralic language-speakers, which includes Hungarian, Finnish and Estonian, and Yeniseian-language speakers, of which only one remains today and is spoken in central Siberia. The middle grouping, which they term "steppe-forest", includes Turkic- and Mongolic-speaking populations from the Volga and the region around the Altai and Sayan mountains, near to where Russia, China, Mongolia and Kazakhstan meet. The southernmost grouping, "southern-steppe", includes the rest of Turkic- and Mongolic-speaking populations living further south, such as Kazakhs, Kyrgyzs and Uzbeks, as well as Indo-European-speaking Tajiks.

Previously unknown genetic connections revealed

Because the study includes data from a broad time period, it is able to show shifts in ancestry in the past that reveal previously unknown interactions. For example, the researchers found that the southern-steppe populations had a larger genetic component from West and South Asia than the other two groupings. This component is also widespread in the ancient populations of the region since the second half of the first millennium BC, but not found in Central Kazakhstan in earlier periods. This hints at a population movement from the southern-steppe region to the steppe-forest region that was previously unknown.

"Inner Eurasia has functioned as a conduit for human migration and cultural transfer since the first appearance of modern humans in this region. As a result, we observe deep sharing of genes between Western and Eastern Eurasian populations in multiple layers," explains Jeong. "The opportunity to find direct evidence for the hidden old layers of admixture, which is often difficult to appreciate from present-day populations, is very exciting."

"We found not only corridors, but also barriers for migrations," adds Balanovsky. "Some of them separate the historical groups of populations, while others, like the distinct barrier following the Great Caucasus mountain ridge, were obviously shaped by the geographic landscape."

Geographic locations of the Eneolithic Botai, groups including newly sampled individuals, and nearby groups with published data. The map is overlayed with ecoregional information, divided into 14 biomes downloaded from https://ecoregions2017.appspot.com/ (credited to Ecoregions 2017 © Resolve). Credit: Jeong & Balanovsky et. al. 2019. The genetic history of admixture across inner Eurasia. Nature Ecology & Evolution, http://dx.doi.org/10.1038/s41559-019-0878-2.

Two ancient individuals resequenced in this study originated from the Botai culture in Kazakhstan where the horse was initially domesticated. Analysis of the Y-chromosome (inherited along the paternal genealogical lines) revealed a genetic lineage which is typical in the Kazakh steppe up to the present day. But analysis of the autosomes, which both parents contribute to their children, show no trace of Botai ancestry left in present-day people, likely due to repeated migrations into the region both from the west and the east since the Bronze Age.

The researchers emphasize that their model of three groupings does not perfectly explain all known populations and that there are examples of both outliers and intermediate groups. "It is important to organize a future study for further sampling of sparsely populated regions between the clines, for example, Central Kazakhstan or East Siberia," states Johannes Krause, also of the Max Planck Institute for the Science of Human History, and senior author of the paper.

Researchers from the study conducting field work along the Amur River. Credit: Yuri Bogunov

Press release from the Max Planck Institute for the Science of Human History / Max-Planck-Institut für Menschheitsgeschichte