Modern Humans Have Weaker and Lighter Bones Than Their Ancient Ancestors

It turns out that our modern lifestyles may have made our bones weaker. Scientists have studied the bones of hundreds of humans who lived during the past 33,000 years and found that over time, human bones became lighter and weaker.

"There was a lot of evidence that earlier humans had stronger bones and that weight-bearing exercise in modern humans prevents bone loss, but we didn't know whether the shift to weaker bones over the past 30,000 years or so was driven by the rise in agriculture, diet, urbanization, domestication of the horse or other lifestyle changes," said Christopher Ruff, one of the researchers, in a news release.

The researchers focused on Europe and took molds of bones from museums' collections. They used a portable X-ray machine to scan them, focusing on two major bones from the legs and one from the arms. By comparing lower limbs with the upper limbs, they could determine whether the changes they saw were due to mobility or to something else, like nutrition.

"By analyzing many arm and leg bone samples from throughout that time span, we found that European humans' bones grew weaker gradually as they developed and adopted agriculture and settled down to a more sedentary lifestyle, and that moving into cities and other factors had little impact," said Ruff.

The researchers found that there was a decline in bone strength between the Mesolithic era, which began about 10,000 years ago, and the age of the Roman Empire, which began about 2,500 years ago. Arm bone strength, though, remained fairly steady. This suggests that the decline continued for thousands of years and that people had a very long transition from the start of agriculture to a settled lifestyle.

The findings reveal that when it comes to bone strength, Paleolithic humans win out. However, by doing more exercise, it's possible for modern humans to achieve stronger bones.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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