Painting with Blood: Ritual, the Body, and the Chemistry of the Huashan Rock Art

Along the limestone cliffs above the Mingjiang River in Guangxi, southern China, roughly 1,300 human figures, some barely 20 centimeters tall and others reaching 3 meters, were painted between the fifth century BCE and the second century CE by the ancient Luoyue people. The Zuojiang Huashan Rock Art Cultural Landscape has stood exposed to two thousand years of monsoon rain, heat and humidity on open rock faces, conditions that should have stripped most mineral pigments long ago. A 2026 study led by Meng Wu of Shandong University, working with the Guangxi Museum of Nationalities, has identified why the red paint held: it wasn't bound with plant gum or plain lime. It was bound with blood, and the researchers think they can say whose.

A Recipe, Not Just a Pigment

Analyzing samples taken from fallen rock fragments at three sites within the landscape, Wu's team found the red color comes from a clay rich in nano-scale hematite. What holds that pigment to bare limestone for two millennia is a separate ingredient: a mortar of slaked lime mixed with blood. As that mixture reacted with air, blood proteins induced the formation of biomineralized calcium carbonate, crystals that encapsulated the hematite particles and fused the whole mixture chemically to the rock surface, rather than simply sitting on top of it. The team estimates that as little as eight milliliters of blood was needed to bind one square meter of painted surface — a small quantity with an outsized structural effect, and the actual explanation for a durability problem that had puzzled conservators for years.

Whose Blood, and Why It Might Matter

The more provocative claim concerns the blood's source. The analysis detected proteins associated specifically with pregnancy and the postpartum period, leading the team to propose the blood was collected from women during or shortly after childbirth. If that holds, the choice may not be incidental to what the paintings show. Earlier iconographic work on the site, notably Qian Gao's 2013 study in Rock Art Research, reads Huashan's dominant motif — squatting human figures with bent, raised arms, alongside painted bronze drums — as imagery tied to Zhuang frog-god and thunder-god worship, connected to the historical Maguai festival's rain and fertility rites. A pigment deliberately mixed with birth blood, in a rock art tradition already saturated with fertility symbolism, would mean the binder and the imagery were expressing the same idea through different means: one legible to the eye, one only to modern protein analysis.

Blood Claims Have a Rocky History

That interpretation deserves to be held a little more cautiously than the chemistry itself, because claims about ancient blood on stone have a mixed scientific record. Thomas Loy's foundational 1983 paper in Science, reporting blood residues identified by species on prehistoric stone tools, opened an entire subfield of residue analysis, including attempts to date and interpret rock art through surviving blood traces. Much of that early work, built on immunological and crystallization techniques, later proved vulnerable to contamination and false positives, and a number of Loy's own species and dating claims were subsequently challenged or rejected by other researchers. The 2026 Huashan study rests on a different foundation: targeted identification of specific proteins through modern analytical chemistry, not the broader, less specific tests that undermined confidence in the field decades ago. That distinction is exactly what a claim this striking needs to survive scrutiny — and exactly what the subfield's history says should not be waived on the strength of an appealing story alone.

What makes Huashan's case worth taking seriously is that the material evidence and the pictorial evidence point in the same direction independently, chemistry describing a substance whose cultural meaning the site's imagery had already suggested on its own. Whether that convergence holds up under further testing, it marks a shift in what rock art analysis can now ask: not just what an image depicts, but what the artists deliberately put into the paint itself, and why.

References

1. Wu, M., et al. (2026). Blood-Induced Biomineralized Calcium Carbonate Used for Binding in the Huashan Rock Art of Guangxi, Southern China. Journal of Archaeological Science, 193, 106650.
2. Gao, Q. (2013). The Huashan Rock Art Site (China): The Sacred Meeting Place for Sky, Water and Earth. Rock Art Research, 30, 22-32.
3. Loy, T. H. (1983). Prehistoric Blood Residues: Detection on Tool Surfaces and Identification of Species of Origin. Science, 220(4603), 1269-1271.
4. UNESCO World Heritage Centre. Zuojiang Huashan Rock Art Cultural Landscape.