Study models the transition from Neanderthals to modern humans in Europe

Using a specially developed simulation model, researchers at the University of Cologne have traced and analysed the dynamics of possible encounters between Neanderthals and anatomically modern humans on the Iberian Peninsula during the Palaeolithic period for the first time. Between approximately 50,000 and 38,000 years ago, the first anatomically modern humans arrived in Europe, where they encountered Neanderthal populations. The team analysed the respective settlement areas and the movement patterns of both groups. Were there any interactions between the groups, and did they mix? And how were population dynamics influenced by climatic events?

The results of the study “Pathways at the Iberian crossroads: Dynamic modelling of the Middle-Upper Paleolithic Transition” led by Professor Dr Yaping Shao from the Institute of Geophysics and Meteorology were published in the journal PLOS One. This study was conducted within the framework of the HESCOR research project at the University of Cologne, in collaboration with Professor Dr Gerd-Christian Weniger (Emeritus) of the Department of Prehistoric Archaeology.

The researchers used a numerical model to simulate exploratively the possibility of both groups meeting on the Iberian Peninsula. The model takes into account the prevailing climate fluctuations and simulates the populations of both groups as well as their connectivity and interaction. It is able to dynamically simulate a wide variety of scenarios, in contrast to more traditional archaeological and genetic methods. It makes it possible to examine different theories and to create a new perspective.

“By linking climate, demography, and culture, our dynamic model offers a broader explanatory framework that can be used to better interpret archaeological and genomic data,” says Professor Weniger from the Department of Prehistoric Archaeology.

During the transition from the Middle to the Upper Palaeolithic, Neanderthal populations across Europe, especially on the Iberian Peninsula, experienced a steady decline leading to their extinction. At the same time, anatomically modern humans spread across Europe. This period was also characterized by strong climatic fluctuations, with alternating cold and warm phases: rapid warming phases occurring over only a few centuries contrast with more gradual cooling periods (so-called Dansgaard–Oeschger events), which are interrupted by severe cold phases caused by massive iceberg discharges into the North Atlantic (Heinrich events).

The precise timing of the Neanderthals’ extinction and the arrival of modern humans remains unclear, so a potential encounter between the two species cannot be ruled out. Genetic analyses of bones from archaeological excavations in comparison with today’s population indicate a mixing in eastern Europe in the early migration phases of modern humans. Later mixing of the two populations on the Iberian Peninsula is possible due to substantial dating uncertainties, but has not yet been proven.

”Repeated runs of the model with different parameters allow for an assessment of the plausibility of different scenarios: an early extinction of the Neanderthals, a small population size with a high risk of extinction, or a prolonged survival that would allow mixing,” says Professor Shao, principal investigator of the study. In most of the runs, however, the two groups did not meet.

In all three scenarios, the population is highly sensitive to climatic fluctuations. In those cases where the population could remain stable long enough, mixing of the two species was possible. With a low probability (1 per cent), at the end of the simulations there are small proportions of 2 to 6 per cent of the total population that have genes from both groups. This mixing would have been most likely in the north-west of the Iberian Peninsula, an area where modern humans could have arrived early enough before the Neanderthal population collapsed completely.

In further studies, the researchers plan to improve both the numerical model and the potential field required for it. In addition to human populations, the model should also include animals that can serve as potential prey. The vegetation data required for this is fed into a potential field, which is calculated separately for humans and animals from a variety of climatic and geographical data. The researchers are also currently investigating whether a specialized machine learning algorithm can help with this.

The HESCOR (Human & Earth System Coupled Research) project pursues interdisciplinary research questions that bring together Earth system science, human-system modelling, and the humanities to investigate how interactions between nature and culture have shaped and continue to shape our world. Experts in climate science, archaeology, mathematics, and the humanities contribute diverse perspectives and cutting-edge methods to research aimed at addressing fundamental questions in human history. How have climatic changes influenced the course of human cultural evolution? To what extent do human decisions and social changes affect the Earth system? Can modern computer tools and machine learning unlock the secrets of our past? HESCOR is funded by the ‘Profilbildung’ initiative of the Ministry of Culture and Science of the state of North Rhine-Westphalia.

END