This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: The Huashan rock art landscape in southern China, close to the border with Vietnam, is a remarkable UNESCO World Heritage site. Thousands of images are painted on river cliffs across more than 80 locations stretching 260 kilometers (162 miles).
They depict people, musical instruments, boats, animals, weapons and many other figures, and date back at least 2,000 years. One of the most puzzling aspects of these ancient depictions is how they have managed to survive in such good condition for so long. The region has an extreme subtropical monsoon climate, with scorching summer heat, heavy monsoon rain and frequent typhoons.
The answer, according to a new study published in the Journal of Archaeological Science, could be that the paint contains a binder made of lime mortar mixed with blood. To study the paintings without damaging them, the research team collected fallen rock fragments from the base of three different sites. They used scanning electron microscopy to examine the individual paint layers and spectroscopy to determine the mineral and chemical composition.
Finally, they tested the samples for ancient organic binders. The analysis showed that the red pigment in the paint appeared to come from local red clay, which contains microscopic iron oxide particles (nano-hematite). The scientists found that these pigment particles were encapsulated in the outer layer of a man-made mortar containing lime and blood, raising the question of why it was added.
The researchers speculate that blood was used for both practical and symbolic reasons. First, it may have served as a natural chemical hardener. When mixed with lime, blood proteins trigger a reaction that causes calcium carbonate to form around the pigment particles.
This may have locked the pigment directly to the cliff like concrete. "This stable organic-inorganic composite bonding system reveals the complex technological processes used by the creators," the study authors commented in their paper. The ancient artists belonged to the Luoyue people, a matriarchal society.
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