By Lisa Rapaport (Reuters Health) – When humans invented the wheel and domesticated horses thousands of years ago, enabling a transition from hunting and gathering to farming, they also started developing weaker bones that make modern people more susceptible to fractures and osteoporosis, according to a new study. Scientists analyzed the remains of Europeans who lived at various times over the past 33,000 years and found the more stationary lifestyle afforded by farming – not the rise of cities or changes in diet – appears to have led to thinner, more brittle bones in modern humans, compared to our “caveman” ancestors. “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 if the shift to weaker bones was driven by the rise in agriculture, or by other causes like diet or urbanization,” said Dr. Christopher Ruff, director of the Center for Functional Anatomy and Evolution at Johns Hopkins Medical Center in Baltimore who led the study published May 18 in the Proceedings of the National Academy of Sciences.