A new protocol for radiocarbon dating of hair and keratin type samples—application to an Andean mummy from the National Museum of Natural History in Paris

The protocol of preparation of keratinized samples (e.g. hair, furs …) for radiocarbon dating that we have developed is based on the selective extraction of keratin from the bulk part of the shaft (cortex). The aim of this method is to eliminate the cuticle which could contain exogenous carbon from external contaminations. The total treatment takes place as follows: a washing/dry cleaning, a soft treatment with diluted acidic and basic solutions (acid/alkali/acid method) similar to the protocol used for vegetal samples, extraction of keratin by reduction using dithiothreitol and precipitation with sodium deoxycholate and trichloroacetic acid. This method was applied on a hair sample from an Andean mummy, conserved in the collections of the Anthropology Laboratory of the National Museum of Natural History (Musée de l’Homme) in Paris, France. The results of two runs reveal that the mummy is dated to a period between the eleventh century and the first half of the twelfth century. It therefore belongs to the Late Intermediate period (900–1450 ad). The combination of historical research, the study of the body by computed tomography and the analysis of mineral deposits on the surface of the body provides clues to identify the geographical origin of the mummy. These investigations led to determine that the mummy comes from the region of Tarapacá in Chile and belongs to the cultural complex Pica-Tarapacá.