TRACKS: An isotopic investigation of the seasonality of Middle and Upper Palaeolithic humans and fauna in Estremadura, Portuga

Abstract

The karstic limestone caves of Portuguese Estremadura provide some of the richest Middle and Upper Palaeolithic archaeological assemblages in Iberia. The well-preserved skeletal remains of Neandertals and anatomically modern humans (AMH) from cave sites such as Gruta da Oliviera, Galeria da Cisterna and Gruta do Caldeirão are invaluable sources of biogeochemical information, and they offer a rare opportunity to address questions about mobility patterns and subsistence strategies in multiple human species diachronically, through direct isotopic investigation.

This research represents the first large-scale isotopic study of human and animal mobility during the Middle and Upper Palaeolithic in Europe. Using laser ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICP-MS), highly spatially resolved sequential strontium isotope analyses of Pleistocene tooth enamel from sites in Portuguese Estremadura are carried out alongside sequential oxygen isotope analysis, in order to reconstruct the mobility of terrestrial fauna across the local landscape. The extreme variation in the geology (and hence 87Sr/86Sr) of the study area over distances of just tens of kilometres permits the detection of relatively short-distance mobility in the region over annual scales. Sequential strontium isotope data from the tooth enamel of two Neanderthals (Pike et al., unpublished), a Magdalenian human (Pike et al., unpublished), and two Solutrean humans (this study) are considered in the context of strontium and oxygen isotope data from contemporaneous fauna, in order to investigate the relationships between human mobility, animal mobility and seasonality across the Middle and Upper Palaeolithic. These data are further synthesized with existing archaeological evidence from the study sites and surrounding region, in order to address wider questions about range size and changes in subsistence behaviour in response to climatic and environmental change.

Results suggest that red deer, ibex, horse and extinct rhinoceros would have been present within a 30km radius of the study sites, and were likely available as resources throughout the year. Based on strontium isotope data and studies of lithic raw material sources, the mobility of both Neanderthals and AMHs appears to be consistent with ranges of between 20-30km, though both isotopic and archaeological evidence suggest that the pattern of landscape changed over time. Settlement patterns appear to have shifted from short term, possibly seasonal residential mobility during the Middle Palaeolithic, to more logistical mobility patterns during the Upper Palaeolithic; perhaps as a response to changing arboreal cover during the climatic oscillations of the Late Pleistocene.

This study further considers our current collective understanding of the complex nature of enamel formation, and its implications for the interpretation of highly spatially resolved isotopic analyses in both archaeological and modern contexts. The potential for the strontium isotope analysis of biological apatites via LA-MC-ICP-MS in seasonality studies is reflected in the data presented here, and suggestions for further refinement of the method (particularly with regard to our understanding of isotope incorporation) are put forward.

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Identifiers

ORCID for Alistair Pike: orcid.org/0000-0002-5610-8948

ORCID for Simon Davies: orcid.org/0000-0003-1830-5403

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