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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - PALEODEM (Late Glacial and Postglacial Population History and Cultural Transmission in Iberia (c.15,000-8,000 cal BP))

Teaser

Summary

The aim of this project is to investigate the population history and processes of cultural transmission from the Late Magdalenian to the Late Mesolithic in SW Europe. This period witnessed major environmental changes and cultural transformations on settlement distribution, technology and social organisation. Our project specifically addresses two major inter-related topics: Firstly, to what extent demographic behaviour was driven by environmental factors; and secondly, how did regional population patterns influence cultural transmission processes.
To answer these research questions, this project addresses three main objectives: First, to reconstruct the population patterns of the Iberian Peninsula from 15,000 to 8,000 cal BP comparing three different geographic scales (micro-regional, regional and macro-regional); second, to examine the role of gradual and punctuated processes of climate change on prehistoric hunter-gatherers demography, evaluating the resulting multi-scalar patterns in the archaeological record; and third, to examine how demographic patterns and inter-regional social networks affected cultural change, particularly at end of the Paleolithic and the Late Mesolithic periods.

The study of Late Glacial and Postglacial demographic dynamics and social networks raise relevant questions for todayâ€™s society given its broader implications to understand processes of cultural evolution, human resilience to climate change and Europeanâ€™s genetic inheritance.

Work performed

In the following, we detail the work performed from the beginning of the project to the end of the period covered by the report (30 months) in each working package.

At WP1 we have completed the fieldwork at the Early Holocene open-air sites of arenal de la Virgin and Casa Corona. Different post-excavation analysis have been completed and are sublect of different scientific papers under preparation. The micro-stratigraphic and micromorphological analyses of combustion structures -including the the preparation of thin sections from the combustion structures and stratigraphic sections- have been already completed as well as most of the analytical work. The multi-sample radiocarbon dating program has been already completed. The intra-site spatial and lithic analyses at both sites are in progress.

For the WP2 we have completed and updated the radiocarbon database and deposited a first version in the Zenodo repository associated to the project. New ad hoc R and Python scripts for the statistical analysis of radiocarbon time series have been created. During the reporting period, we have conducted the first complete analysis of Summed Probability Distributions of calibrated radiocarbon dates (SPDs) for the Iberian Peninsula and the different regional subsets. In addition, we have been performed Paleoclimatic correlations with the Global and Mediterranean paleoclimatic proxies.
The results of the work developed in this WP we have been published is scientific paper in the journal Nature Communications in Open Access.

Regarding the WP3, we have completed the georeferenced database of cultural attributes for the Network Analysis. A first theoretical and methodological review of the state of the art according to recent published literature on networks has been performed and a first publication about the methodological-theoretical approach has been submitted.

For the reporting period the team members have presented 21 conference papers at international meetings where we have co-organized three sessions and one international workshop. The dissemination actions for the general public cover 4 interviews in TV and radio station programs, a fieldwork open day visit, 10 press releases and the participation in one exhibition at the National Museum of Science and Technology (Alcobendas, Madrid).

Final results

At the current stage of the work (30 month), we would like to highlight two major results that show the progression of the action beyond the state of the art.

First, at the micro-regional scale, the excavation results at the Arenal de la Virgen site and the integrated geoarchaeological, chronological and paleoecological program represent one of the very few case studies with multi-proxy evidence of severe impacts of the 8.2 kya cold climatic event on human systems. Particularly, the work performed conciliates human occupation and paleoecological records at a local scale, in one of the most arid areas of Southwestern Europe long the Early Holocene providing a secure framework to analyse regional population dynamics. In addition, it must be stressed the focus on open-air sites, usually underrepresented in the archaeological record and long- term research programs of southern Europe. Other expected results for the second reporting period are related with the reconstruction of climatic and paleoatmospheric conditions at local scale through the stable isotope analyses of land snail shells recovered from Mesolithic combustion features.

Second, this project has reported the first reconstruction of long- term changes in population size during the Last Glacial-Early Holocene transition in Iberia through the statistical analysis of the radiocarbon record. We have uncovered evidence of relative population changes and developed a best-fitting demographic model composed by three different phases. Our findings suggest that the population of Iberia increased during most of GI-1 until a rapid decrease occurred at the onset of the YD stadial, subject to certain variability at regional and sub-regional scales, which was followed by a sustained period of stationary growth. During the second half of the Early Holocene (c. 10.2-8 kya), we identified a recovery of relative population levels, when growth rates were similar or slightly greater than those of the first phase, but this soon attenuated towards a pattern of fluctuation around stationary growth. Importantly, this pattern of population dynamics agrees with recent aDNA studies, suggesting that a major population turnover occurred in Europe at the end of the Late Glacial, but we can now also suggest that the timing of this process can be pushed slightly forward to encompass the Younger Dryas and the Early Holocene of the Iberian Peninsula and the rapid environmental changes that occurred. Our modelling results illustrate that human populations have an inherent capacity for rapid growth, but it seems that in the past this was often checked by the constraints of the environment, especially for prehistoric hunter-gatherers during episodes of climate change.
The expected results until the end of the project are mainly related with WP3, the study of cultural transmission processes using social network analysis and network modelling. Here, we aim to simulate different demographically-dependant hypotheses of technological change during the Epipaleolithic and the Late Mesolithic period and test them against the empirical record (in form of spatial networks of sites and cultural attributes). Certainly, this kind of hypothesis-driven approach has the potential of moving the of study cultural transmission processes in hunter-gatherers well beyond the state of the art.