Discovery reveals when and where horses were first tamed for domestic use

All domestic horses, from sleek racetrack champions to sturdy draft breeds, trace their lineage back to the western Russian steppes in the third millennium BCE.

Despite their common ancestry, the timeline and process through which horses were domesticated and integrated into human societies have long been subjects of academic debate.

Recent breakthroughs in genetic research have shed light on these historical mysteries, revealing that the widespread use of domestic horses began around 4,200 years ago.

This pivotal moment significantly enhanced communication and trade across Eurasia, fostering an era of unprecedented cultural exchanges.

Tracing the genetic footprint of domestic horses

The research was led by Ludovic Orlando, director of the Centre of Anthropobiology and Genomics of Toulouse. The study involved 133 researchers from 113 institutions worldwide, marking a significant milestone in the field of genetic archaeology.

By analyzing a vast array of horse archaeological remains across the Eurasian continent, the team employed radiocarbon dating alongside ancient DNA sequencing.

This approach enabled them to construct a detailed genetic timeline that clarifies the evolutionary adaptations coinciding with the advent of equestrianism.

Pablo Librado, the study’s first author from the Institut de Biologia Evolutiva of Barcelona, reflected on the evolution of this research field.

“A decade ago, we only had access to a handful of ancient genomes. Today, we’ve analyzed several hundreds, allowing us to resolve longstanding debates about the role of horseback riding in massive human migrations from the steppes approximately 5,000 years ago,” noted Librado.

Three pillars of horse domestication

The researchers focused on three key indicators of early horse husbandry. They first traced the expansion of domestic horse progenitors beyond their initial domestication zone.

Next, they mapped out horse demography throughout the third millennium BCE to pinpoint the earliest signs of systematic breeding and large-scale production.

Lastly, they identified significant shifts in horse reproductive lifespans, suggesting early breeders’ deliberate efforts to manipulate animal reproduction.

These combined findings align around 4,200 years ago, suggesting that it was only then that domestic horses were bred in numbers large enough to meet the growing demand across the continent.

This era marks the true beginning of horse-based mobility, which remained the fastest mode of terrestrial transportation until the 20th century.

Genetic insights and historical impacts

The study also addressed the genetic changes in Europeans during the first half of the third millennium BCE, a period marked by significant human migrations from the steppes, likely by proto-Indo-European language speakers.

The researchers found that changes in the domestic horse genetic map occurred much later, allowing them to dismiss horseback riding as a primary driver of these human migrations, despite the common linguistic roots related to horses.

Orlando highlighted the breakthrough in understanding horse breeding scales. “For years, I wondered how such a substantial number of horses could suddenly be bred from a relatively small area to meet global demands by the second millennium BCE. We discovered that breeders significantly reduced the time between generations, essentially doubling their production rate,” he explained.

The team’s innovative method for measuring generational times offers a new perspective in archaeozoology. It calculates the number of mutations and DNA crossovers in genomes to establish a direct timeline of generational changes.

This methodology not only sheds light on horse breeding but also provides insights into the generational intervals of other domestic species and even our hunter-gatherer ancestors.

Complexity of domestic horse history

Further complicating the history of horse domestication are findings from Botai, a Central Asian site known for its evidence of horse milking, harnessing, and corralling.

The study revealed unusually short generational intervals in a distinct horse lineage at Botai, supporting theories that settled human groups there domesticated horses for consistent access to resources like meat and milk.

Unlike their counterparts, these Botai horses did not contribute to the genetic pool that expanded across Eurasia.

Milestones in horse domestication

The research concludes that there were likely two distinct phases of horse domestication. The initial phase, around 5,500 years ago, aimed to stabilize declining horse populations for sustenance in Central Asia.

The more transformative second phase, around 4,200 years ago, introduced fast mobility on a scale that had never been seen before, profoundly influencing the course of human history.

This study not only illuminates the complex genetic history of domestic horses but also enhances our understanding of human-animal relationships and their impact on societal developments across millennia.

The study is published in the journal Nature.

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