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Published March 31, 2023
A former University of Wyoming graduate student’s analysis of the remains of a 17th century horse in southwest Wyoming played a key role in a new study showing that Indigenous people were using horses in the American West earlier than documented previously.
Cassidee Thornhill, who earned her bachelor’s and master’s degrees in anthropology from UW, published the results of her analysis in the journal Plains Anthropologist in 2021. That research is cited in a new publication in the journal Science, involving researchers at dozens of institutions, showing that horses were being used by Native Americans in the Northern Rockies and central plains before 1650. Previously, it was thought that horses descended from those brought from Europe in the 1500s didn’t reach the Rocky Mountain West until around 1700.
“These insights provide additional information for the timeline of the introduction of the horse into the High Plains and demonstrate the horse was playing some role in Native lifeways soon after horses were brought from Europe to the Americas,” says Thornhill, who now works as a lead archaeologist with Transcon Environmental.
The horse remains she analyzed as a graduate student, held in UW’s Archaeological Repository, were found years earlier near the Blacks Fork River in what is now the Ashley National Forest near Flaming Gorge Reservoir. It was a young horse -- just 5 or 6 months old -- but its bones show chop marks and other clear signs of modification by humans.
Thornhill’s analysis also included radiocarbon dating showing that the horse lived and died around 1640 -- earlier than the previous most commonly accepted time of around 1700 for horses to have arrived in what is now Wyoming.
The Blacks Fork horse features prominently in the new paper published in Science by lead author William Taylor, from the University of Colorado. Thornhill is listed as one of the co-authors of the study, which included radiocarbon dating of 23 historical horse specimens in North America.
The researchers concluded that dispersal of domestic horses from Spanish settlements in the American Southwest to the northern Rockies and central Great Plains took place by the first half of the 17th century, at the latest. This happened via Indigenous people, who were raising, feeding, caring for and using horses for transportation.
The research “shows that horses were present across the plains long before any documented European presence in the Rockies or the central plains,” the researchers wrote.
Specific to the Blacks Fork horse, the new paper says the findings “have deep ramifications for our understanding of social dynamics in the Great Plains during a period of disruptive social changes for Indigenous peoples.”
That part of southwest Wyoming is considered to be a homeland for the ancestral Comanche, who were connected by language and more to the ancestors of today’s Eastern Shoshone tribal members on Wyoming’s Wind River Indian Reservation. The Comanche migrated to the southern plains of Texas, New Mexico, Colorado and Oklahoma before the early 18th century.
The drive to acquire horses from Spanish New Mexico has been cited as a likely reason for the Comanche migration, but the new research suggests that the Comanche had already integrated horse raising, ritual practices and transportation at least 50 years before their southward migration. Once they were on the southern plains, the Comanche built an empire on the horse and bison trade by around 1750.
“By the time Europeans arrived in southwestern Wyoming, the area was already a critical ‘secondary diffusion center’ for horse transmission to Northern Plains groups,” the researchers wrote. “Considering the small body of archaeological data available, our findings raise the possibility of rapid, non-European transmission of horses farther northward, including the Columbia Plateau, the Canadian Rockies, and the middle and upper Missouri regions.”
Thornhill’s 2021 paper cited previous research noting historical documents that referred to livestock raiding by the Apache, Navajo and Ute people by the early 1600s -- which likely resulted in the spread of horses to other groups. These horses mostly likely descended from horses brought to the first Spanish settlements in New Mexico around 1598.
“Most likely, via the Ute, with whom they are related, the Shoshone, in southwestern Wyoming, obtained the horses by the 1640s …,” Thornhill wrote.