Research Article: Pego do Diabo (Loures, Portugal): Dating the Emergence of Anatomical Modernity in Westernmost Eurasia

Date Published: January 27, 2010

Publisher: Public Library of Science

Author(s): João Zilhão, Simon J. M. Davis, Cidália Duarte, António M. M. Soares, Peter Steier, Eva Wild, John Hawks.

Abstract: Neandertals and the Middle Paleolithic persisted in the Iberian Peninsula south of the Ebro drainage system for several millennia beyond their assimilation/replacement elsewhere in Europe. As only modern humans are associated with the later stages of the Aurignacian, the duration of this persistence pattern can be assessed via the dating of diagnostic occurrences of such stages.

Partial Text: In the ongoing debate concerning the emergence of anatomical modernity [1]–[16], the Iberian Peninsula occupies a particular place. Current evidence suggests that, south of the Ebro drainage system, Neandertal populations persisted for several millennia after their disappearance everywhere else. In one model—the “Ebro Frontier” [17]–[22]—this time lag was caused by historically contingent demographic and paleoenvironmental factors, with replacement/assimilation ensuing once such factors ceased to operate and along the same lines as in the rest of Europe. Others have suggested that the Iberian pattern is a byproduct of erroneous dating and insufficient data, creating the illusion of punctuation in a process that would have been characterized by a straightforward East-West gradient [23]–[25].

The bladelet tools from layer 2 of Pego do Diabo are associated with a faunal assemblage of Early Upper Paleolithic composition and dated by chemically reliable samples to the time range of the Aurignacian III–IV. Besides scant recent Holocene intrusions, no other component exists in these deposits, as corroborated by the fact that, despite having consumed in the process 42% of all the piece-plotted bones recorded therein, our dating project returned for samples from layers 2 and 2D no results of intermediate age. Typological and technological considerations exclude assignment of the Pego do Diabo Dufours to earlier phases of the Aurignacian or to the Gravettian. The inescapable conclusion is that a human occupation of Aurignacian III–IV cultural affinities took place at Pego do Diabo ca.29–30 ka 14C BP (ca.33.5–34.5 ka cal BP), i.e., in the lower end of the 95% confidence interval of the conventional bulk bone date obtained 20 years ago.

All animal bones and teeth were examined, but only certain regions of some of the bones were recorded in detail and counted. The criteria applied when deciding whether to record a particular fragment of bone or tooth, and how they are counted, are described elsewhere [65], [99]. The Parts of the Skeleton Always Counted (PoSAC) are similar to Watson’s “diagnostic zones” [100]. For example, the medial half of the articulation of the distal tibia is counted, but none of the following parts of a tibia would be counted: the lateral half of the distal articulation, diaphysis, and proximal end. These “counted parts of the skeleton” include the mandibular cheek teeth, and articular ends/epiphyses and metaphyses of girdle, limb and feet bones. They are the units used to calculate the frequencies of different parts of the skeleton and proportions of young (epiphysis unfused) versus adult (epiphysis fused) animals. When other parts of the skeleton such as antlers, horn cores or maxillary teeth are the only evidence for the presence of a species, these non countable specimens are recorded and their presence denoted by a “+” sign, but not included in the total counts of species found. The reasons for selecting these particular parts are as follows: a) they are relatively easy to identify to species; b) some, such as the distal metacarpal in certain species of artiodactyls, when in sufficient quantity, can provide information about the sex ratio; c) many include a separate centre of ossification, or epiphysis, which fuses to the rest of the bone at a particular age and so, in sufficient quantity, provide a ratio of juveniles to adults; d) many provide useful measurements; and e) they come from most regions of the skeleton (head, girdles, limbs and feet) and their relative abundance indicates possible preferences for different parts of the body such as non-meat bearing versus meat bearing parts or fore quarters versus hind quarters.



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