­As women across the world fight for recognition of their rights and equal representation, a recent archaeological discovery in the north of China shows why undoing discrimination is such an uphill struggle: Sexism is ancient.

A team of paleontologists led by Ekaterina Pechenkina, professor of paleoanthropology at Queens College, part of the City University of New York, has been analyzing the skeletal remains of men and women from the Neolithic—Stone Age—Yangshao culture (5000-3000 BCE) and comparing them to human bone fragments from the Bronze Age Eastern Zhou dynasty (770 BCE-221 BCE), all found in northern China’s Yellow River Basin.

The findings are startling. During the long time span that separates the two cultures, a significant shift in diet had taken place, as new grains entered the region, adding wheat and barley to the late Neolithic millet-rich table. As time went by, humans in this part of the world also started to rely less heavily on tending pigs and hunting, and more on domesticated herbivores like the rabbit–reflecting a restructuring not only of eating habits, but also of economic and social activities.

“Through stable isotope analysis of a total of 46 specimens, we were able to collect a robust body of evidence for an inference of male-biased inequality during the Bronze Age in China,” explains Pechenkina. Her team’s analytical observation of skeletal remains in burial grounds in the Central Plains showed that by the Eastern Zhou period female bones were shorter than before, and female skulls presented cranial lesions associated with poor nutrition.

“Malnourished people simply do not grow to their full genetic potential,” says Pechenkina, “and given that the [Chinese] Central Plains skeletal collections come from a fairly uniform genetic background and environmental setting, changes in male-female post-cranial dimensions over time likely reflect sex-specific parental investment.”

In other words, in the long time span separating the Yangshao culture from the Eastern Zhou, something important changed in early Chinese society—perhaps the nearly constant state of war among rival kingdoms that characterizes this time, also known as Warring States period—that pushed parents to feed their male children more, and with foods that were more nutritious than what they were giving their baby daughters.

“The skeletal stress-markers in females [due to insufficient nutrition] are very clear and consistent, and they simply do not appear in the samples we have studied from early farming communities,” explains Pechenkina. “Female discrimination seems to have been intertwined with the rise of social complexity.”

The findings brought to light by Penchenkina and her team are still at an early stage, and more research is needed to arrive at clearer generalizations over precisely what changes occurred, what caused them and how widespread they were. But already scholars are intrigued by the potential of this method of inquiry.

“There were really major social changes that happened in the Eastern Zhou,” says Professor Sarah Allan, from Dartmouth College, “But usually, when people talk about rising inequality of women they talk about the Han dynasty (206 BCE-220 AD). This research would imply that in the Eastern Zhou at least, men and women consumed their meals separately.”

The different bone composition could point to inequalities having arisen even earlier, although evidence is scant for now, says Allan. “The Warring States period (475-221 BCE) saw a breakdown of the lineage system that existed before, with a lot of social changes and social mobility: How did this affect gender?” says Allan.

For now, though, the dietary deficiencies in the female skeletons “fit the fact that this was a very male-centered society,” says Lothar Von Falkenhousen, professor of Chinese art and archaeology at the University of California, Los Angeles. They also suggest sexism was spread across classes, he explained.

“Female status was determined by male status, and females received fewer privileges than males, as can be seen by comparing how elaborate the burials of noblemen or women could be,” he says. But the true novelty revealed by this analysis is that “some kind of discrimination might have existed also at lower levels of society,” says Von Falkenhousen.

He also noted that the skeletal analysis approach used by Pechenkina’s team allows for the gathering of information even in the absence of a burial setting rich in ritual objects or written records, both typical of people from the lowest classes, offering more complete information on the lifestyles of the time.

The findings might be preliminary, but “they give scholars a new tool that allows new questions to be asked,” said Von Falkenhousen.

Skeletal stable isotope analysis might be a new tool in the hands of the archaeologists, but it’s revealed the old roots of a contemporary problem: Even back in the Central Plains of ancient China, nearly 3,000 years ago, being male was easier than being female.