Comment on "DNA from Pre-Clovis Human Coprolites in Oregon, North America" Paul Goldberg,1,2,* Francesco Berna,1,3 Richard I. Macphail1,4
Gilbert et al. (Reports, 9 May 2008, p. 786) presented DNA analysis of coprolites recovered from an Oregon cave as evidence for a human presence in North America before the Clovis culture. Results of our micromorphological and Fourier transform infrared spectroscopy analyses of one of the reported coprolites are difficult to reconcile with the DNA results identifying the coprolite as human.
1 Department of Archaeology, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA.
2 Zentrum für Naturwissenschaftliche Archäologie, Universität Tübingen, Rümelinstraße 23, 72070 Tübingen, Germany.
3 Dipartimento di Scienze della Terra "Ardito Desio," Università degli Studi di Milano, Via Mangiagalli 34, 20133 Milano, Italy.
4 Institute of Archaeology, University College London, Gordon Square, London WC1 0PY, UK.
* To whom correspondence should be addressed. E-mail:
paulberg@bu.eduGilbert et al. (1) report the recovery, dating, and DNA analysis of coprolites from Paisley Cave, Oregon, which they ascribe to a human presence in North America about 1000 years before the Clovis culture. In 2007, the authors of the study asked us to perform micromorphological and Fourier transform infrared (FTIR) spectroscopy analyses on one of the coprolite specimens (1374-5/5D-31-2), but our results were not included in the published report (1). Here, we present the results of our 2007 analyses, as well as analysis of a second subsample of specimen 1374-5/5D-31-2, supplied by Gilbert et al. in 2009.
The subsamples we examined in 2007 and 2009 were described as follows (2): This specimen was found on the edge of the "bone pit" that included camel, horse, and sheep bones, a horse hoof, and other items. It is 27 mm long by 25 mm wide by 15 mm thick and appears to have an exterior surface on one side. Constituents include vegetation, feathers or fibers of some kind, small bones, and some dirt. Sample preparation, manufacture of thin sections, and micromorphological examination were carried out using protocols established in (3) and the supporting online material. The use of micromorphology (the study of intact sediments, soils, and materials) was a natural analytical procedure because it uses intact pieces of sample, which preserves the integrity and initial geometric arrangement of all of the components within the sample (3).
Microscopic evaluation of the 2007 subsample (Fig. 1) revealed the predominance of fibrous, elongated vegetative fragments, including some phytoliths. Its external morphology resembled that of herbivore dung pellets, including the typical stained outer surface (4, 5). Internally, the coarse character of the plant fibers, as observed in reference thin sections of herbivore dung (e.g., camel, cattle, goat, mouflon sheep, and sheep) and as reported from the dung of browsers (6, 7), is also consistent with that of herbivores. The FTIR analysis shows the presence of silicates (in the 450 to 1100 cm–1 region) and organic material (in the 1300 to 4000 cm–1 region), which are compatible with decayed organic compounds; no minerogenic phosphate was noted (Fig. 2). If phosphate is present, it is likely to be in a dominantly organic form and in low quantities (0.565% P), as is typical of dry farmyard manure [table 11.1 in (
]. Examples of human coprolites and cess (mineralized sewage) are phosphate rich, containing 8 to 14% P and mean 6.57% P, respectively (9).
http://www.sciencemag.org/cgi/content/full/325/5937/148-c
