How has a famous group of 2,000 year-old Chinese rock paintings remained so vibrant? Because it was made with blood, new research says

Shandong University researchers led by Meng Wu say the bright red Huashan rock paintings in Guangxi’s Zuojiang River Valley stayed vivid for about two millennia because the paint included blood. Unesco-listed cliff murals (roughly fifth century BC to second century AD) sit on limestone in a hot, humid monsoon climate. The team sampled fragments from three of more than 80 sites. Red clay rich in nano-hematite was the pigment, with a lime-and-blood mortar as binder. Slated for the Journal of Archaeological Science. An outside specialist said the childbirth-blood claim is the weakest part.