Study reopens debate over when horses were first ridden: full analysis

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A new Science Advances analysis is reopening one of archaeology's biggest animal questions: when did people really begin domesticating and riding horses? The authors argue that recent work has leaned too heavily on the emergence of the DOM2 genetic lineage around 2200 to 2100 BCE, effectively treating that moment as the start of domestication. Their counterargument is that the human-horse relationship began earlier and unfolded in stages, with management, milking, and riding appearing before the genetic signature that later came to dominate modern horses. (phys.org)

That debate has been building for years. In 2021, a widely cited Nature study concluded that modern domestic horses originated from a Western Eurasian steppe lineage, DOM2, which then spread quickly and replaced earlier horse populations across Eurasia. That work also pointed to selection at genes including GSDMC and ZFPM1, interpreted as potentially relevant to back conformation, stress tolerance, and behavior important for equestrian use. In 2024, another Nature paper and broad news coverage reinforced the idea that widespread horse-based mobility emerged around 2200 BCE, tightening the link between DOM2 and true domestication. (nature.com)

The new paper pushes back on that framing. According to coverage based on the study and the University of Helsinki team, the authors argue that early taming and organized horse use were already happening in the 4th millennium BCE, possibly earlier, across several horse populations labeled DOM1, DOM2, and a proposed DOM3. They contend that Yamnaya groups were already riding horses before 3000 BCE, even if those animals were not yet part of the fully domesticated lineage that later swept across Eurasia. In this view, full domestication shortly before 2000 BCE was an endpoint in a longer process, not the beginning of it. (phys.org)

That interpretation also draws strength from older archaeological evidence that has never fit neatly into a single-lineage model. Botai sites in Kazakhstan have long been central to the domestication debate because of evidence interpreted as corralling, milking, and bridling. But later genomic work showed Botai horses were linked to the lineage leading to Przewalski's horse rather than to modern domestic horses, prompting some researchers to downgrade Botai's role. Subsequent reviews, however, have argued that Botai may still represent meaningful horse husbandry or specialized horse pastoralism, even if it was not the direct source of today's domestic breeds. (nature.com)

Expert reaction in the broader literature suggests the field is still far from settled. Reviews in Frontiers in Environmental Archaeology have described horse domestication as a multi-centered, multi-stage process and argued that evidence for riding likely predates the explosive spread of DOM2. Earlier commentary around the 2024 genomic work also emphasized that the rapid rise of DOM2 does not automatically erase prior experimentation, management, or regional domestication pathways; rather, it may show which lineage ultimately won out under later selection pressures. That leaves room for the new paper's central point: genetic success and first domestication may not be the same event. (frontiersin.org)

Why it matters: For veterinary professionals, this is more than an archaeology dispute. It speaks to how equine traits were shaped over millennia, and why modern horses reflect both ancient adaptation and much more recent, intensive breeding. The same literature notes that selective breeding in the modern era sharply narrowed male lineages, reduced heterozygosity, and increased genetic load, with implications for inherited disease, performance, and welfare. A more layered domestication history may also help explain why behavior, musculoskeletal resilience, and management responses vary so widely across horse populations and breeds. (frontiersin.org)

For clinicians and equine industry professionals, the practical takeaway is that domestication should be understood as a continuum of management, selection, and changing human use, not a single genetic threshold. That framing better matches what veterinarians see in practice: the horse as a species shaped by work demands, handling, reproduction, and human preference over very long timescales. It also underscores the value of preserving genetic diversity as breeding goals continue to evolve. (frontiersin.org)

What to watch: The next phase will likely focus on whether more ancient genomes, direct evidence of milking and bridling, and additional skeletal markers in both horses and riders can pin down where early management ended and full domestication began, and whether the proposed DOM3 population holds up under further study. (phys.org)