A shared commitment to an evolutionary approach promoted a close alignment between prehistoric archaeology and ethnology in western Europe and the United States beginning in the 1860s. In Europe, the foundation for this alignment was the belief in unilinear cultural evolution forged a century earlier by Enlightenment philosophers. It was accepted that arranging modern cultures in a series from simplest to most complex illustrated the earlier stages through which the most advanced cultures had developed in prehistoric times. French and British Palaeolithic archaeologists did not try harder to elucidate the past using archaeological data because their commitment to unilinear evolutionism led them to believe that ethnology revealed almost everything they wished to know about prehistoric times.

In the United States, where it was assumed that relatively little cultural evolution had occurred in prehistoric times, archaeology, ethnology, physical anthropology, and linguistics had begun by the 1840s to be regarded as different branches of anthropology, which was identified as the study of American indigenous peoples.