title: Spatial gradients in Clovis-age radiocarbon dates across North America suggest rapid colonization from the north.
abstract: A key issue in the debate over the initial colonization of North America is whether there are spatial gradients in the distribution of the Clovis-age occupations across the continent. Such gradients would help indicate the timing, speed, and direction of the colonization process. In their recent reanalysis of Clovis-age radiocarbon dates, Waters and Stafford [Waters MR, Stafford TW, Jr (2007) Science 315:1122-1126] report that they find no spatial patterning. Furthermore, they suggest that the brevity of the Clovis time period indicates that the Clovis culture represents the diffusion of a technology across a preexisting pre-Clovis population rather than a population expansion. In this article, we focus on two questions. First, we ask whether there is spatial patterning to the timing of Clovis-age occupations and, second, whether the observed speed of colonization is consistent with demic processes. With time-delayed wave-of-advance models, we use the radiocarbon record to test several alternative colonization hypotheses. We find clear spatial gradients in the distribution of these dates across North America, which indicate a rapid wave of advance originating from the north. We show that the high velocity of this wave can be accounted for by a combination of demographic processes, habitat preferences, and mobility biases across complex landscapes. Our results suggest that the Clovis-age archaeological record represents a rapid demic colonization event originating from the north.
authors: Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA. marcusj@unm.edu
authors: Marcus J
authors: MJ
authors: Hamilton
authors: Briggs
authors: B
authors: Buchanan
mesh_terms: D000884:Anthropology, Cultural; D000885:Anthropology, Physical / Q000379:methods*; D002250:Carbon Radioisotopes / Q000032:analysis*; D005260:Female; D006801:Humans; D007198:Indians, North American; D007231:Infant, Newborn; D008297:Male; D008954:Models, Biological; D009656:North America; D010163:Paleontology; D036801:Parturition; D011157:Population Dynamics; D012098:Reproduction; D013995:Time
chemical_list: D002250:Carbon Radioisotopes