Theories explaining the significance of exotic artefact traditions in their social contexts allow plausible interpretations to be made of archaeological findings. European conquest so devastated the empires of Mexico and the Andes and their cultural traditions, that until the 1960s it was assumed that archaeological discoveries could only be interpreted by art-historical analysis of images. In the Andes, with no ancient written records, periods have had to be dated by technologies that measure changes in the composition of materials found in the archaeological layers, such as radio-carbon analysis. Archaeologists were studying Moche remains from the early twentieth century, but only began to work on the pot iconography in the 1960s and 1970s. The interpretation of Moche iconography draws an analogy with the way scenes such as the Nativity, Last Supper, and Crucifixion, which dominate Christian iconography, are sometimes conflated with minor themes and characters to represent key concepts in Christian cosmology and ritual.