Scientists explore origins of horse riding through human skeletons

As anyone who has ever spent time in the saddle knows, riding a horse can be taxing on the body. But can it change the appearance of your skeleton?

The answer, according to archaeologists at the University of Colorado Boulder: It’s complicated. In a new study, the team drew on a wide range of evidence, from medical studies of modern horsemen to records of human remains spanning thousands of years.

The researchers concluded that horseback riding can indeed leave a mark on the human skeleton, for example by subtly altering the shape of the hip joint. But these changes alone cannot definitively reveal whether people rode horses during their lives. Many other activities, even sitting for long periods, can also transform human bones.

“In archaeology, there are very few cases in which we can unequivocally link a particular activity to skeletal changes,” said Lauren Hosek, lead author of the study and assistant professor in the Department of Anthropology at CU Boulder.

She and her colleagues published their findings on September 20 in the journal Scientific progress.

These findings could have implications for researchers studying the origins of human horse domestication, and also cast doubt on a long-standing theory in archaeology known as the Kurgan hypothesis.

The first horsemen

The research goes to the center of one of archaeology’s long-standing debates, said William Taylor, co-author of the new study and curator of archaeology at the University of Colorado Museum of Natural History.

He explained that the first indisputable evidence of the use of horses as a means of transportation by humans comes from the Ural region of Russia. There, scientists have discovered horses, bridles and chariots dating back about 4,000 years.

But the Kurgan hypothesis, which emerged in the early 20th century, argues that the close relationship between humans and horses began much earlier. Its proponents believe that around the fourth millennium B.C., ancient people living near the Black Sea, called the Yamnaya, began galloping across Eurasia on horseback. In doing so, they spread an early version of the languages ​​that would later evolve into English, French, and other languages.

“Much of our understanding of the ancient and modern worlds hinges on when people began using horses as transportation,” Taylor said. “For decades, it has been thought that the spread of Indo-European languages ​​was somehow linked to the domestication of the horse.”

Recently, scientists have highlighted human remains from the Yamnaya culture dating back to around 3500 B.C. as key evidence for the Kurgan hypothesis. According to the group, these ancient peoples had signs of wear on their skeletons, likely from horseback riding.

Hips can be extended

But in the new study, Hosek and Taylor argue that the story is not so simple.

Hosek has spent a lot of time studying human bones to learn from the past. She explained that the skeleton is not static, but can move and change shape over the course of an individual’s life. If you stretch a muscle, for example, there can be a reaction where the muscle attaches to the underlying bone. In some cases, the bone can become more porous or raised ridges can form.

However, reading these types of clues can be difficult, such as the hip joint for example.

Hosek noted that when you flex your legs at the hips for long periods of time, including during long horseback rides, the ball and socket of the hip joint can rub against each other along one edge. Over time, this friction can cause the round socket of the hip bone to become elongated or oval. But, she added, other activities can cause the same type of elongation.

Archaeological evidence shows that humans used cattle, donkeys, and even wild asses to get around in parts of Western Asia centuries before horses were tamed. Ancient peoples likely harnessed these beasts of burden to pull carts or even smaller, two-wheeled vehicles that resembled carts.

“Over time, this intense, repetitive pressure from this type of jostling in a flexed position could cause skeletal changes,” Hosek said.

She observed similar changes, for example, in the skeletons of 20th-century Catholic nuns. They never rode horses, but took long carriage rides across the American West.

Ultimately, Hosek and Taylor say human remains alone cannot be used to date when people began riding horses, at least not with the scientific data currently available.

“Human skeletons alone won’t be enough,” Hosek said. “We need to combine these data with evidence from genetics and archaeology, as well as the study of horse remains.”

Taylor added that the picture does not look good for the Kurgan hypothesis:

“At least so far, none of this evidence suggests that the Yamnaya people owned domestic horses.”