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LAte Glacial RANGe Expansion

Periodic Reporting for period 1 - LAGRANGE (LAte Glacial RANGe Expansion)

Reporting period: 2016-04-01 to 2018-03-31

From around 25 to 20 thousand years ago, during the so-called Last Glacial Maximum, most of northern Europe was covered by ice and humans retreated into refuges in the warmer southern territories. The archaeological record of the Western European Late Pleistocene clearly indicates a refuge encompassing the areas of Cantabria, in northern Spain, and Aquitaine, in southern France. Both archaeological and genetics evidence agrees that it was from this “Franco-Cantabrian” refuge that Western Europe was repopulated in several phases starting at around nineteen thousand years ago.

As pioneer groups expanded their ranges into previously uninhabited northern territories, Late Glacial hunter-gatherers had a unique opportunity to engineer their evolving ecosystem or niche. According to the Niche Construction Theory (NCT) paradigm such practices deeply change the selective pressures of that niche on its populations, both human and non-human, thus affecting not only cultural transmission, but also biological/genetical transmission: a triple inheritance model.

The LAGRANGE project will study the Late Glacial hunter-gatherer range expansions, and the role of niche construction in these. This will be achieved by an interdisciplinary approach to the problem applying established Computer Science methods to archaeological data. Firstly, triple-inheritance models will be developed to understand how niche construction affects the dispersal dynamics of a given population. This new understanding will then be integrated with a method for the numerical simulation of dispersals, known as the Fast Marching Method. This method allows for complex variables to be dealt with, whilst being considerably faster than the more traditional approach of solving differential equations. Such a NCT-modified Fast Marching method will then be used to model the Late Glacial dispersals of humans on a biogeographically realistic domain. This approach will help identify routes, preferred habitats and other dispersal choices taken by the expanding groups.
Work involved the numerical modelling and analsysis of the dynamics of a spread ing niche constructing trait. This resulted in the observation that niche constructing traits spread at a rate that is given by the standard reaction-diffusion equations. Phase B of the project invovled the collection and analysis of radiocarbon data associated with human presence in Western and Central Europe during the Last Glacial Maximum (LGM) and Late Glacial periods (roughly 30k-18k BP). This involved an extensive literature review, which highlighted the problems and flaws with currently available datasets. Despite their flaws, these datasets provide consist results when analysed for their palaeodemographic signals, showing a limited bottleneck effect during the LGM, but a significant rise in the meta-population of Europe during the Late Glacial period. Furthermore, one well curated dataset for the Central European Magdalenian allowed for a statistical analysis of the the potential refugia zones, as well as routes of spread, of humans north after the LGM, revealing the presence of at least a second refugia in Eastern Europe.

Dissemination wise, a key methodological paper focused on the analysis of paleodemography together with dispersal dynamics, but applied to the better understood spread of the Neolithic, was published in Scientific Reports. A second, shorter review of the state of the art is currently in press (PAGES magazine).
The project has moved the state of the art bar, by applying innovative paleodemographic techniques to the time period and region in questions, which throws questions over the received knowledge that there was s significant population bottleneck duing the LGM. Furthermore, the dispersal analysis, adds considerable weight to the on-going discussion around the role of glacial microrefugia, and the potential existence of northern refugia for humans during the LGM, from which they would have recolonized central and eastern Europe.
Western Europe at the end of the Last Glacial Maximum (c. 18,000 BCE)