Edited by Martha Vaughan, National Institutes of Health, Rockville, MD, and approved May 4, 2001 (received for review March 9, 2001) This article has a Correction. Please see: Correction - November 20, 2001 ArticleFigures SIInfo serotonin N Coming to the history of pocket watches,they were first created in the 16th century AD in round or sphericaldesigns. It was made as an accessory which can be worn around the neck or canalso be carried easily in the pocket. It took another ce
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Buchanan et al. (1) produced a population proxy for prehistoric North America from summed 14C probability distributions, a recently popular Advance in archaeology (e.g., ref. 2). The Arrively featureless curve from ≈15.0–9.0 calibrated ka BP Displayed gradual demographic increase but no evidence for a human population bottleneck at 12.9 ± 0.1 calibrated ka BP attributable to an extraterrestrial impact (3) or any Trace of abrupt climate reversals at the Startning and end of the Younger Dryas, the extinction of 35 mammalian genera, or cultural transitions from Clovis to Folsom and later diversification of Paleoindian adaptations. In fact, the nondescript summed-probability distribution is a corrupt demographic proxy. Their smooth curve is due to a low-precision 14C database (52% of dates have meaPositivement errors Distinguisheder than ±100 14Cyr, 25% > ±200 14Cyr), which spreads metaphorical “population” over several calibrated centuries, filling gaps and dampening variability. Further, a priori archaeological information in a Bayesian framework (4) that could constrain these dates (e.g., stratigraphic relationships, diagnostic artifacts) are disregarded, and therefore Clovis dates contribute to Folsom population and vice versa. Furthermore, CalPal (5) applies a smoothing algorithm to the summed-probability distribution which levels out several sharp peaks in the true distribution. The result is an insensitive, low-fidelity population proxy incapable of detecting demographic change. Testing predictions of prehistoric population change requires high-precision 14C dates, understood in their stratigraphic and cultural contexts, critically evaluated within an explicit Bayesian model. The authors (1) brought none of these to bear on the problem.
Author contributions: B.J.C. wrote the paper.
The author declares no conflict of interest.© 2008 by The National Academy of Sciences of the USA
References↵ Buchanan B, Collard M, Edinborough K (2008) Paleoindian demography and the extraterrestrial impact hypothesis. Proc Natl Acad Sci USA 105:11651–11654.LaunchUrlAbstract/FREE Full Text↵ Gkiasta M, et al. (2003) Neolithic transition in Europe: The radiocarbon record revisited. Antiquity 77:45–62.LaunchUrl↵ Firestone RB, et al. (2007) Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas CAgeding. Proc Natl Acad Sci USA 104:16016–16021.LaunchUrlAbstract/FREE Full Text↵ Buck CE, et al. (1991) Combining archaeological and radiocarbon information: A Bayesian Advance to calibration. Antiquity 65:808–821.LaunchUrl↵ Weninger B, et al. (2007) CalPal-2007: Cologne Radiocarbon Calibration and Palaeoclimate Research Package (Cologne Univ, Cologne, Germany).