If you’re a hard-working lady, you probably already suspected what scientists have confirmed today: prehistoric women worked their butts off.

The bones of 94 women who lived in farming communities in Central Europe from 5300 BCE to around 850 AD reveal that prehistoric women had stronger arms than living women, including semi-elite female rowers. That’s likely because these farming women from the past worked incredibly hard — tilling soil, harvesting, and grinding grain by hand. And they probably started at a very young age, according to a study published today in Science Advances.

The findings show that prehistoric ladies didn’t leave the physical labor to the men. In fact, they toiled long hours and were a key “driving force” behind the social and cultural development of agricultural communities over almost 6,000 years, says lead author Alison Macintosh, an anthropologist at Cambridge University. “Now we can kind of see, actually there’s these thousands of years of rigorous manual labor that had been completely underestimated,” she tells The Verge. “It’s really important to be able to understand the contribution of women.”

When trying to re-create how men and women behaved in the past, and their roles in society, scientists have to look at the archaeological evidence, which includes tools, as well as skeletons. Bones function as a sort of hard drive, storing all kinds of information about nourishment and physical activity throughout a person’s life. If you work out a lot, you won’t just have stronger muscles but also stronger bones. “Your bones are really an excellent biological record of your life,” says Brigitte Holt, a biological anthropologist at the University of Massachusetts Amherst, who was not involved in the research.

Previous studies looking at prehistoric bones showed that when hunter-gatherers picked up agriculture and settled down, their legs got weaker and arms got stronger. That’s because these people stopped wandering around as much, becoming more sedentary and tending to crops and livestock. But these changes were more pronounced in men than women, says Macintosh, partly because men’s bones respond differently to physical activity. For that reason, comparing women’s and men’s bones is not a good way to understand just how much work women did compared to men.

“They just look much weaker than men, so we think they’re not doing anything when that’s really not the case,” Macintosh says. “You need an appropriate comparison to see that.” That’s why Macintosh and her team decided to put prehistoric female bones side to side with modern female bones.

She scanned the upper arm bones and shinbones of 94 women from the Neolithic to the Middle Ages, as well as the bones of 83 living women in Cambridge who either led a sedentary lifestyle, or practiced sports such as soccer, running, or rowing. Old and modern bones were then compared to each other. The researchers found that the prehistoric women had consistently stronger arms: the Neolithic women living about 7,000 years ago had 11 to 16 percent stronger arm bones than modern rowers, for instance, while Bronze Age women from about 4,000 years ago had 9 to 13 percent stronger arms than the rowers. That suggests women were working hard with their arms, but also that they likely started working when they were kids, when bones are still growing, Holt tells The Verge.

The leg bones, however, told a different story: some prehistoric women had weaker legs than today’s women, while others had legs as strong as those of runners. “It suggests that women were doing a huge range of things,” Macintosh says. Some might have had very strong leg bones because they walked a lot, tending to grazing cows and fetching water over long distances, for instance, while other women might have been more sedentary, grinding grain all day to make flour.

The study has some limitations: the researchers couldn’t take into account genetic factors, for instance, which can influence whether a person has stronger bones than another. All the living women in the study were also from Cambridge, so results could be different for women living elsewhere. Still, it’s an “excellent study,” Holt says, that finally confirms what scientists have long suspected: that prehistoric women were hard workers — and we all have to thank them for that.

“This kind of work just highlights the role of women in the development of life as we know now,” Macintosh says. “We all pretty much live in agricultural societies now. And these couldn’t have developed without all of this manual labor done by women over thousands of years.”