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From planting crops and grinding grain to caring for domestic animals, prehistoric women performed so much manual labor that it left its mark on their bones.

A new study looked at remains from Neolithic, Bronze Age, and Iron Age cemeteries and compared them with bones from modern female athletes. The results show that prehistoric women were positively brawny—their arms were almost uniformly stronger than those of today’s champion rowers.

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“This is the first paper that compares the bones of prehistoric women to those of living women, and it has allowed us to identify a hidden history of consistent and rigorous manual labor among women across thousands of years of farming,” says study coauthor Alison Macintosh of the University of Cambridge.

The study, published today in Science Advances, suggests that women were a driving force behind the development of agriculture during its earliest 6,000 years in Central Europe.

“We often think about men as the ‘providers,’ but this paper really highlights women's extensive contribution to provisioning,” says Marshall University’s Habiba Chirchir, who was not part of the study team. (Find out about the yield gap between modern men and women farmers.)

Advent of Agriculture

For much of our history, humans survived by being nomadic, hunting and foraging wherever resources were naturally found. Developing a reliable system of local food production, aka farming, emerged relatively recently, within the last 12,000 years in the Levant and even more recently in Europe.

Figuring out the labor roles among these early men and women is crucial for anthropologists studying how prehistoric societies reorganized themselves as agricultural practices and technologies developed. One way to do this is by looking for the effects of activity on bones, such as changes in shape, density, thickness, and curvature.

But so far, most of these skeletal studies only assessed men’s bones and looked for signs of load-bearing activities. This is largely because male skeletons are simply more common in ancient cemeteries, says the University of Pisa’s Damiano Marchi, and because the ways in which male bones respond to activity are more robust and better understood.

The few studies that looked at women compared female bones to male bones, which muddied a substantial portion of the picture. Macintosh and her colleagues weren’t satisfied, so they set out to study the bony indicators of activity in both ancient and modern women.

Well Armed

The team’s prehistoric bones came from cemeteries tucked throughout Central Europe, from the Serbian border into western Germany. These remains date to about 5,300 B.C. through A.D. 850. (Find out what genetics reveal about the roots of modern Europeans.)

They also CT scanned the bones of modern Cambridge athletes and community members, specifically semi-elite rowers, football players, endurance runners, and sedentary non-athletes. They screened the participants to exclude anyone with injuries or illnesses that might affect their bones.

View Images The researchers used CT scans to create 3-D models of the bones from European prehistoric women, akin to this one of an upper arm bone from a prehistoric North African agriculturalist. Image courtesy Dr Alison Macintosh

The team compared the shape and strength of both the humerus in the upper arm and the tibia in the lower leg among dozens of these ancient and modern women. They found that prehistoric women’s upper arm bones almost uniformly contained more changes associated with load-bearing activities. Bronze Age women were disproportionately strong, they say, indicating that their behaviors were dominated by intense and repetitive manual labor.

“We can really start to see signatures of rigorous labor being performed by women over thousands of years,” Macintosh says. “That was essentially hidden before, when we only had male comparative samples.”

Though their arms were steely, prehistoric women had variably strong legs, with some similar to today’s ultramarathon runners and others weaker than the most sedentary participants. That explains why earlier studies focusing on the tibia failed to reveal the extent to which women worked, Macintosh and others say.

Worked to the Bone

It’s not clear which exact activities ancient women were performing, but Macintosh has a list of possibilities, based on the fact that plows and other tools hadn’t been invented yet: tilling soil, planting crops, harvesting crops, grinding grain, milking livestock, processing meat, making textiles, making pottery—for hours and hours each day.

While we may not know the specific activities, the results support a substantial role for women in shepherding a new way of life into Central Europe, says Duke University’s Steven Churchill.

“In lots of early agricultural societies, diets were supplemented by hunting, so perhaps the women were doing more of the field labor,” he says. Churchill adds that early agriculturalists had a much tougher time than their nomadic, hunting-gathering predecessors. They had to work harder while handling harsher living conditions and more diseases.

“People didn't adopt agriculture because they saw it as being better than foraging,” he says. “They did it because they had to, probably because increasing population density was making foraging untenable.”

That means women may have been literally shouldering a great deal of the agricultural burden. Last year, Macintosh and her colleagues reported that as Central European societies transitioned from hunting to farming, women were more negatively impacted than men: Their skeletons showed greater signs of severe developmental stress and poor health.