Monday, October 18, 2004

Athena Review, Peopling of the Americas: Pedra Furada, Brazil: Paleoindians, Paintings, and Paradoxes

Athena Review, Peopling of the Americas: Pedra Furada, Brazil: Paleoindians, Paintings, and Paradoxes

Athena Review, Vol.3, no.2: Peopling of the Americas

Pedra Furada, Brazil: Paleoindians, Paintings, and Paradoxes
An interview with Drs. Niède Guidon†, Anne-Marie Pessis†*, Fabio Parenti†,Claude Guérin**, Evelyne Peyre~, and Guaciara M. dos Santos‡

†Serra da Capivara National Park and Fundação Museu do Homem Americano (FUMDHAM), Brazil; *University of Paris / University of Pernambuco; **Dept. of Earth Sciences, Université Claude Bernard, Lyon; ~Centre National de la Recherche Scientifique (CNRS), Biological Anthropology Laboratory, National Museum of Natural History, Paris, France; ‡Dept. Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University / Earth System Science Department, Univ. California, Irvine

Pedra Furada in northeastern Brazil represents possibly the oldest known human site in the Americas. Since C-14 dates of 48-32,000 BP were reported in a Nature article (Guidon and Delibrias 1986), the site’s Paleoindian components have been highly controversial, challenged (though not refuted) by many North American researchers (e.g. Meltzer, Adovasio, and Dillehay 1994). Yet the site has solid evidence of non-Clovis, Paleoindian occupations including human remains, plus a unique rock painting tradition from at least 12,000-6,000 BP. In March, 2002, Athena Review (AR) asked archaeologist Niède Guidon and her colleagues to explain the current status of the findings, including both Paleoindian skeletal and subsistence remains, and the abundant rock paintings at Serra da Capivara National Park, which contains Pedra Furada (figs.1,2). Much of the interview is given here (for full text, see printed issue of AR, V3, no.2)

Fig.1: Sandstone outcrops at Capivara National Park in Brazil, containing the Pedra Furada Rock Shelter (photo: FUMDHAM).]

Dating of Pedra Furada:

AR: Based on your 1986 Nature article and several recent web reports, your sites have a wide range of dates, some as early as 48-30,000 years BP with two hearth samples dated at 32,000 BP, and evidence of cave painting (a fragment with two ochre-drawn lines) associated with a 17,000 year old C-14 dated hearth. How are these dates holding up as your work progresses?

Niède Guidon: These dates are holding well. Once we learned that the Department of Earth Sciences of the Australian National University had developed a new chemical technique to decontaminate small quantities of charcoal to be dated by AMS (accelerator mass spectrometry), we sent samples to Canberra from the same charcoal dated in 1988/91 by the Gif laboratory in France. The results are given here by Dr. Guaciara M. dos Santos.

Guaciara dos Santos: A comprehensive chronology of human activity at the Boqueirão da Pedra Furada (BPF) site, the oldest archaeological site found at the Capivara National Park (fig.3), has been established by reliable radiocarbon dates on charcoal excavated from different levels. The sub-phase BPF 1, the lowest layer with definite evidence of human activity in the Pedra Furada Rock Shelter, gave radiocarbon results ranging from 35,000 to greater than 48,000 BP (Guidon and Arnaud 1991; Parenti 1996). For the oldest samples, the 48,000 lower limit is imposed by the residuals remaining after conventional acid-wash or acid-base-acid chemical pre-treatments. These pre-treatments are intended to decontaminate samples with traces of extraneous, more modern carbon which may be present, as the result of exposure of charcoal in this layer to the environment.

A new ABOX-SC (acid-base-wet oxidation followed by stepped combustion) procedure, developed by Bird et al. (1999), which has been instrumental in establishing secure radiocarbon dates of greater than 40,000 for the human occupation of Australia (Turney et al. 2001), has now been applied by me to charcoal from the oldest occupation layer of the Pedra Furada site. This more rigorous chemical pre-treatment, which was followed by a stepped combustion (SC) procedure to remove any residual contamination, decontaminates samples from charcoal and wood (Bird et al. 1999; Santos et al. 2001), enabling credible radiocarbon dating to around 55,000 BP.

A total of seven charcoal samples from hearths at site BPF 1 were subjected to the full ABOX-SC procedure and their radiocarbon contents were determined by accelerator mass spectrometry at the Australian National University. Five of the samples proved to be even beyond the limit of this new technique, returning ages of greater than 56,000 BP. Finite ages of 53,000 and 55,000 BP were obtained for the remaining two (Santos et al., in manuscript).

These new results push back the time of human occupation at the Pedra Furada site by at least another 8,000 years relative to the previous results. Hence, it appears that humans were already at this site about 60,000 years ago, and possibly even earlier.

Fabio Parenti: The radiocarbon dates at the site of Pedra Furada, totaling 52 in my final report (Parenti, in press) are fully confirmed by new AMS techniques, especially for the oldest unit, Pedra Furada 1, which is now dated to at least 50,000 years BP.

[Fig.2: Paleoindian site locations in east Brazil including Serra da Capivara National Park and Lagoa Santa.]


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