Prehistoric Climate Change and Horses: A Regional View
Global research on prehistoric wild horses since the last Ice Age gives us a good overview of what occurred during this period. Worldwide scientists tell us horses dwarfed and even disappeared from most of their original sites—modern day Asia and North America.

That’s the global view. But what happened, exactly, on a regional level?

Swiss scientists recently set out to learn how local horse populations changed. Specifically, they looked at their own region—a world utterly devoid of any free-ranging horses for the last several millennia. And this new, local look, they say, gives a whole new view into how horses dealt with the Last Glacial Maximum (LGM), a period of extreme cold and aridness (water was bound in huge glaciers) during the most recent Ice Age.

“In contrast to the development in the heartland of wild horse distribution (the Eurasian steppe region), where horse populations declined after the LGM, they were expanding in the region of present-day Switzerland,” said Julia Elsner, PhD, of the University of Basel’s Integrative Prehistory and Archaeological Science department.

In their study, Elsner and her fellow researchers investigated 92 archaeological horse remains from nine sites, most of them in the mountainous area of the Swiss Jura. The bones and teeth ranged in age from 41,000 to 5,000 years old. That period covers the times before and after the LGM, which ended about 21,000 years ago, she said.

Their findings indicated that, unlike farther west in Asia, horses in their region survived the Ice Age and thrived, taking advantage of newly exposed grasslands.

“The population present after the LGM expanded into a newly accessible landscape, which had been covered by glaciers before, and actually outnumbered the previous population,” Elsner said.

But that ideal situation wouldn’t last. “When the climate changed into warmer conditions, vegetation changed, and the whole environment became less favorable for wild horses who were adapted to cold and arid weather and open steppe,” she said.

Their research also revealed that the region’s horse populations were not constant and were not a series of evolving generations. Instead, they were broken up, with genetically unrelated groups coming and going over thousands of years.

And all this occurred through climate change, not human intervention, she said.

Looking at prehistoric horse populations on a regional level benefits our understanding of equine science and development, as a complement to a global view, the research team said. “This approach has offered the opportunity to focus on aspects of horse population development that might be overlooked in the global picture by demonstrating specific reaction patterns to changing environmental conditions,” they stated.

Since the land became known as Switzerland more than 700 years ago, horses have been admired as a luxury. “There are no free-ranging horses in Switzerland,” Elsner said. “I would guess that there never were. Domestic horses had to be imported and have always been very expensive, prestigious objects.”

The study, “Ancient mtDNA diversity reveals specific population development of wild horses in Switzerland after the Last Glacial Maximum,” was published in PLoS One.