In this this chapter I explore some of the implications of the discovery of unimpeachable evidence for high human antiquity, and the proposition of new biological theory. The bulk of analysis turns on the differences that arose between the stated methodology of prehistoric archaeology, and the actual practice of evolutionary archaeology between the mid 1860s and 1880. I will explain these differences by demonstrating the critical importance of the relationship between prehistoric archaeology and two other fledgling sciences, ethnology, and anthropology. I will argue that essentially the same a priori propositions that ensured the plausibility of the earlier ‘short timescale’ prehistories continued to do so despite the discovery of high human antiquity.