Electron spin resonance dating of human teeth from Toca da Santa shelter of São Raimundo Nonato, Piauí, Brazil

Results of the dating of fossil human teeth excavated from a shelter in the surroundings areas of the Serra da Capivara National Park, São Raimundo Nonato, Piauí, Brazil are presented. This shelter was partially excavated to search for more data that could improve the archaeological context of the Garrincho’s limestone hill sites, where the Toca do Gordo do Garrincho shelter provided two human teeth dated by conventional C-14 in (12,170 ± 40) yBP (years before present) and calibrated age (2 Sigma, 95% probability) 15,245-14,690 yBP (Beta 136204) [E. Peyre, C. Guérin, N. Guidon, I. Coppens, CR Acad. Sci. Paris, Sciences de la terre et des planètes/ Earth & Planetary Sciences 327 (1998) 335, [1]].This region is challenging the classical theories about the peopling of America. In agreement with such theories the first human groups would have arrived in America, through Behring, only about 20,000 years ago. The site Toca do Boqueirão da Pedra Furada is a rock-shelter situated at the cliff that is the frontier between the Pré-Cambrian São Francisco plain and the Devonian-Permian highlands of the Maranhão-Piauí basin. It was excavated from 1978 till 1988 and presented a very consistent stratigraphy, with thousand of lithic implements and hearths [F. Parenti, Le gisement quaternaire de la Pedra Furada (Piaui, Brésil), Stratigraphie, chronologie, évolution culturelle, Editions Recherches sur les civilisations, Paris, 2002, [2]; F. Parenti, Le Gisement Quaternaire de la Toca do Boqueirão da Pedra Furada (Piauí, Brésil) dans le Contexte de la Préhistoire Américaine Fouilles, Stratigraphie, Chronologie, Évolution Culturelle, Ph.D. diss, Ècole des Hautes Ètudes en Sciences Sociales, Paris, 1993, 411p, [3]; F. Parenti, M. Fontugne, N. Guidon, C. Guérin, M. Faure, Chronostratigraphie des gisements archéologiques et paléontologiques de Sao Raimundo Nonato (Piaui, Brésil): contribution à la connaissance du peuplement pléistocène de l’Amérique, Supplément de la Revue d’Archéométrie, 1999, p. 327, [4]].Seventy C-14 dates were obtained going from 59,000 yBP to 5000 yBP at the actual soil [G.M. Santos, M.I., Bird, F. Parenti, L.K. Fifield, N. Guidon, P.A. Hausladen, Quaternary Sci. Rev. 22 (2003) 2303, [5]]. Beneath the date of 59,000 yBP it was found 1.5 m of archaeological layers, till the rock base. The cobbles that composed the structure of the hearths placed on top of the rock base were dated by thermoluminescence and the date of them is 100,000 yBP [H. Valladas, N. Mercier, M. Michab, J.L. Joron, J.L. Reiss, N. Guidon, N., Quaternary Sci. Rev. 22 (2003) 1257, [6]; H. Valladas, N. Mercier, M. Michab, J.L. Joron, J.L. Reyss, N. Guidon, Datações por Termoluminescência de Seixos de Quartzo Queimados da Toca do Boqueirão da Pedra Furada (Piauí, Nordeste do Brasil), Fumdhamentos III, 1 (2003) 35 (in Portuguese), [7]]. Thus chronological information is of paramount importance to contextualize and to understand the many questions regarding the human occupation of these sites [N. Guidon, A.M. Pessis, G. Martin, O Povoamento Pré-Histórico do Nordeste do Brasil, Proposta da: Fundação Museu do Homem Americano, e do Núcleo de Estudos Arqueológicos, da UFPE, CLIO ARQ, Recife 1 (6) (1990) 123, [8]]. To obtain more information Toca da Santa shelter, the nearest site to Toca do Gordo do Garrincho shelter, was also excavated and three incomplete skeletons with teeth were found at 80 cm depth. The teeth were cleaned and acid etched and enamel completely removed from dentine and crushed in particles smaller than 0.5 mm. Enamel was irradiated with a Co-60 source and measured with an ESR spectrometer (X-band) to obtain the signal versus dose curve. The archeological doses obtained by the fitting were (5.94 ± 0.07) Gy and (5.97 ± 0.08) Gy. Using the ROSY program an age of 5,700 ± 200 yBP was found for both teeth.