Human blood has been discovered in 2,000-year-old Chinese rock art

The Huashan rock art site is situated in Guangxi in southern China, not far from the border with Vietnam. Thousands of red images of people, boats, weapons, animals and musical instruments have been preserved on the cliffs along the rivers.

Many of the paintings are over 2,000 years old.

Their preservation has long been a mystery. The region has a climate that is harsh for rock art: hot summers, high humidity, heavy monsoon rains and frequent typhoons.

Nevertheless, a significant proportion of the red figures remain clearly visible after millennia.

Researchers set out to discover how the ancient artists managed to achieve such durability.

Details

To avoid interfering with the site, the scientists did not scrape the paint directly from the rocks.

Instead, they collected fragments of rock that had already broken away at the foot of three sites containing rock art.

The samples were then analysed using electron microscopy and several types of spectroscopy, which enabled the researchers to determine the structure and chemical composition of the finest layers.

Separately, the researchers searched for traces of ancient organic matter.

And it was here that the most unexpected discovery was made.

The red colour of the drawings was provided by local clay containing microscopic particles of iron oxide – haematite.

However, the pigment was not simply bound to the rock surface by water or clay.

The researchers discovered an artificially prepared layer of lime, within which blood proteins—including human ones—had been preserved.

According to the authors’ reconstruction, ancient artisans may have mixed lime with blood, applied the resulting mixture to the stone, and then added a red mineral pigment.

This resulted in a complex organo-mineral material.

The main intrigue lies not only in the mere presence of blood.

Researchers believe that its proteins may have been involved in chemical processes that made the paint layer significantly more durable.

When it interacted with the lime, calcium carbonate formed around the pigment particles. Such mineralisation may have literally ‘trapped’ the particles of red pigment within the solid layer whilst simultaneously binding them to the rock.

In essence, the ancient artists may have created a kind of natural composite combining organic substances and minerals.

It is this mechanism, according to the authors, that may partly explain why the paintings have survived for over two thousand years.

However, the study does not prove that blood was the sole reason for their preservation.

The analysis suggests that the ancient artists may have used blood of various origins.

The researchers detected traces of both animal and human biological material.

It is therefore incorrect to say that all the Huashan rock art was created exclusively using human blood.

Furthermore, the scientists examined samples from only a few areas of the vast complex, so the results cannot automatically be generalised to every image at Huashan.

Nevertheless, the presence of human proteins makes the discovery particularly unusual.

The authors have put forward an even more unusual hypothesis.

Among the proteins identified, they drew attention to compounds that may be present in women’s bodies after childbirth. The researchers suggested that the use of such blood may have had symbolic significance and been linked to beliefs about fertility, life and renewal.

But this part of the study remains a hypothesis.

The scientists were unable to extract ancient DNA, which would have allowed them to determine the origin of the biological material with greater certainty. Furthermore, the proteins found are present in the body not only after childbirth.

It is therefore not yet possible to assert that the ancient images were created specifically using the blood of women in labour.

The creation of the vast Huashan complex was previously considered an extremely labour-intensive undertaking.

The artisans had to work on high, sheer cliffs, haul materials up there and apply large-scale compositions under difficult conditions.

New research suggests that the complexity may also have lain in the very technique used to prepare the paint.

Ancient artists probably did not simply grind red clay and apply it to the rock. They used a multi-component mixture in which lime, organic substances and mineral pigment interacted.

This approach required an understanding of which mixtures would adhere well to the rock and withstand environmental exposure.

Why this is important

This discovery allows us to view the ancient rock art of Huashan not only as an artistic or ritual monument, but also as the result of a complex technique.

If the proposed mechanism is confirmed by further research, the blood may have served a dual purpose: as part of a symbolic ritual whilst simultaneously helping to reinforce the paint layer.

It also suggests that some ancient conservation techniques may have been considerably more complex than the seemingly simple red images on the rock would suggest.

And this unusual mixture may well have been one of the reasons why the figures have survived thousands of years of monsoons, heat and typhoons.

Source

Study: Meng Wu et al. Blood-induced biomineralised calcium carbonate used for binding in the Huashan rock art of Guangxi, Southern China.

Journal: Journal of Archaeological Science, 2026.