Women living in farming communities in Central Europe during the Neolithic and Middle Ages didn’t need to hit the gym to build muscle and strength – the manual labor required to raise livestock and grow crops kept them in better shape than modern elite athletes.

Previous bioarchaelogical investigations of prehistoric behavior have only compared women’s bones to men’s, leading to a systematic underestimation of the nature and scale of physical demands borne by women, according to researchers from the University of Cambridge’s Department of Archaeology.

"This is the first study to actually compare prehistoric female bones to those of living women," said Alison Macintosh, lead author of the study. "By interpreting women's bones in a female-specific context we can start to see how intensive, variable and laborious their behaviors were, hinting at a hidden history of women's work over thousands of years."

The researchers analyzed arm and leg bones from women who lived on farming communities from 5300 BCE to about 850 AD. The bone strength data was compared to those of 83 modern living women – some who lead a more sedentary lifestyle, others who are runners, as well as elite rowers and athletes.

CT scans were taken of the living women’s humerus and tibia bones. The athletes who participated were involved in the Open- and Lightweight squads of the Cambridge University Women’s Boat Club, who broke the course record during this year’s Boat Race. Most of the women were in their early twenties and trained twice a day, rowing an average of nearly 75 miles per week during the study timeframe.

Results showed that the Neolithic women analyzed (who lived 7,400 to 7,000 years ago) had similar leg bone strength to modern rowers, but their arm bones were 11 to 16 percent stronger for their size than the rowers.

This also equated to the Neolithic women having arm strength that was nearly 30 percent higher than average Cambridge University students.

Bronze Age women (who lived 4,300 to 3,500 years ago) showed arm bone strength that was nine to 13 percent stronger than the Cambridge rowers. However, they had 12 percent weaker leg bones. This suggests that Bronze Age women may have focused on duties that required more arm strength but didn’t require as much mobility.

Previous studies have suggested that when hunter-gatherer groups began to move toward agriculture, their legs got weaker and arms got stronger as their lifestyle changed. They stopped migrating as much for hunts, and instead stayed in one place to cultivate land. The biological changes noted in previous studies were more pronounced in men than women, because male bones respond differently to physical activity, according to the Cambridge researchers. Men’s bones respond to strain in a more visibly dramatic way than female bones, which is why it was important to conduct a female-to-female comparison for this study.

The results show that prehistoric women spent hours tilling soil, harvesting and grinding grain by hand – and likely started doing so from a young age.

As the researchers explained in the study, the task of converting grain into flour was a primary activity in early agriculture, and was likely done by women. The daunting task requires the grain be ground by hand between two large stones, which may have been done for up to five hours a day.

"The repetitive arm action of grinding these stones together for hours may have loaded women's arm bones in a similar way to the laborious back-and-forth motion of rowing," said Macintosh.

Additional daily tasks for women would have included collecting water and food for livestock, processing milk and meat, manually planting, tilling and harvesting crops, and converting hides and wool into textiles.

“"Our findings suggest that for thousands of years, the rigorous manual labor of women was a crucial driver of early farming economies. The research demonstrates what we can learn about the human past through better understanding of human variation today," said Jay Stock, senior study author.

The study was published this week in Science Advances.