A funeral mask painted with human blood

THIS FUNERAL mask, photographed by Yoshii Yutaka of the Sicán Archaeological Project, in Peru, was discovered 30 years ago, 800km to the north of Lima. The Sicán were a group who flourished around 500 years before the arrival, in the 1500s, of Europeans. The red paint adorning the mask is made of cinnabar, a compound of mercury and sulphur. But turning cinnabar into paint requires a binding agent—and in this case it must have been a good one, to keep the paint attached to the mask for so long. Luciana da Costa Carvalho of Oxford University therefore set out to discover what it was.Initial mass spectroscopy suggested proteins were involved, but shed no light on which. A follow-up study, however, produced the astonishing suggestion that the binder in question was chimpanzee blood—astonishing because chimps are African, not American animals. Further investigation revealed the mistake. The blood was actually from chimps’ close relatives, .