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 timedelayed 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.Early Paleoindian ͉ wave of advance ͉ landscape complexity ͉ hunter-gatherers ͉ Late Pleistocene

Paleoindian demography and the extraterrestrial impact hypothesis

“…Subsequently, there is a period of rapid population growth. Lasting from 13,100 to 13,000 calBP, this population growth coincides with the efflorescence of Clovis in North America (11,12). Thereafter, population increases reasonably steadily until Ϸ9,500 calBP, when another period of rapid population increase occurs.…”

AMS 14C dating of early human occupation of southern South America

“…Alroy (2001) used the same origin and the same estimates for human mobility and intrinsic rate of increase but with carrying capacity varying dynamically as a function of predator-prey interactions, finding that a colonizing population expanding at that speed could readily induce the observed rates of North American megafaunal extinction. Most recently, Hamilton and Buchanan (2007) fitted a linear least-squares regression model to a very small sample of Clovis-age uncalibrated 14 C dated sites in North America and estimated that initial dispersal from Edmonton (the southern end of the ice-free corridor) took place at about 11,300 BP (95% CI: 11,607 BP), with the population front advancing at a speed of 5-8 km/ 14 C-year. If a North American dispersal event of that age and with the same spread dynamic also gave rise to the first colonization of South America, then the predicted first occupation dates for the earliest southern South American sites in our sample should be of the order of 1500-2400 14 C-years after initial entry (taking Cerro Tres Tetas as a representative example, which is located w12,000 km from Edmonton in Canada on a Great Circle route).…”

Vertical cultural transmission effects on demic front propagation: Theory and application to the Neolithic transition in Europe

“…Front propagation models have been applied to many physical, biological, and cross-disciplinary systems, including combustion flames [1], Taylor-Couette and Rayleigh-Bénard experiments [2], superconductors [3], viral infections [4], tumor growth [5], and human invasions [6][7][8][9][10][11][12]. The latter application is considered in this paper, going beyond previous models by taking the role of cultural diffusion into account.…”