Exploring the two-way migration of Late Pleistocene horses
How did climate change affect horses tens of thousands of years ago? Horses originated in North America around 4 million years ago and later travelled across a landmass created by changing sea levels that bridged the gap between north-eastern Asia and north-western North America. However, modern North American horses are descended from Eurasian lineages later brought by Europeans. An international research team, including 18 indigenous scientists from the Lakota, sqilxʷ (suknaqin/Okanagan Nation), Blackfoot, Dene' (Athabascan) and Iñupiaq Nations looked at modern and ancient DNA samples to investigate. Their findings(opens in new window) were published in ‘Science’. Supported by the EU-funded PEGASUS(opens in new window), Horsepower(opens in new window) and MethylRIDE projects, the researchers applied indigenous and Western scientific methods, including genomics and isotope profiling, on horse fossils. They sequenced the genomes of 68 Late Pleistocene horse specimens from both the American and Eurasian continents – Alaska, Yukon and Siberia. “In this study we harnessed the full power of the latest generation of DNA sequencing instruments, and Lakota scientific genomic principles, to uncover a more complete diversity of horse lineages that existed in these regions during the Late Pleistocene,” explains senior author Ludovic Orlando in an article(opens in new window) published on ‘Phys.org’. Orlando is director of the Centre for Anthropobiology and Genomics of Toulouse, a joint multidisciplinary research centre supported by PEGASUS, Horsepower and MethylRIDE project coordinator French National Centre for Scientific Research and the University of Toulouse.
Movement both ways
The researchers identified three distinct horse lineages in North America alone – one south of the ice sheets, another across Alaska and the Yukon, and a third at the westernmost edge of Alaska. The third horse lineage was found to be genetically related to populations from Eurasia and crossed the land bridging North America and Asia multiple times between 50 000 and 19 000 years ago. Investigations also revealed that horses had travelled in the opposite direction in earlier time periods. They followed coastal routes southward along the Pacific, reaching as far as north-eastern China, eventually leaving genetic traces as far west as Anatolia and the Iberian Peninsula. In the Late Pleistocene, as climate warmed and the ecosystem became much wetter, the land bridge was lost and connectivity between the American and Asian populations ended. This led to the extinction of horses on their continent of origin, explaining why modern North American horses are descended from Eurasian lineages later brought over by Europeans. The findings of the study supported by PEGASUS (The makeup of the modern horse: a history of the biological changes introduced by human management), Horsepower (Horse Power: Interactions between China, Mongolia and the steppe 2000-0 BCE), and MethylRIDE (MethylRIDE: Charting DNA methylation reprogramming of Ice Age horses in the face of global climate change and extinction) highlight the importance of ecological corridors. By supporting continuous movement between habitats, they help preserve the biodiversity of large mammals and their dependent and interrelated life forms. Study co-author Jane Stelkia, an Elder for the sqilxʷ, concludes: “In this study, Snklc'askaxa [the Horse Nation] is offering us medicine by reminding us of the path all life takes together to survive and thrive as life moves and changes. It is time that we come together, again, to help life find the openings and points to cross and move safely.” For more information, please see: PEGASUS project web page(opens in new window) Horsepower project website(opens in new window) MethylRIDE project