Three special Aurignacian sites—Cardina-Salto do Boi, Abrigo de la Malia, and Lapa do Picareiro—are also indicated. Credit: PLOS One (2025). DOI: 10.1371/journal.pone.0339184

Using a specially developed simulation model, researchers at the University of Cologne have traced and analyzed the dynamics of possible encounters between Neanderthals and anatomically modern humans on the Iberian Peninsula during the Paleolithic 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 analyzed 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 modeling of the Middle-Upper Paleolithic Transition," led by Professor Dr. Yaping Shao from the Institute of Geophysics and Meteorology are 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.

Simulation model and research approach

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.

Population decline and climatic influences

During the transition from the Middle to the Upper Paleolithic, 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.

Model scenarios and genetic mixing

"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%), at the end of the simulations, there are small proportions of 2–6% of the total population that have genes from both groups.

This mixing would have been most likely in the northwest of the Iberian Peninsula, an area where modern humans could have arrived early enough before the Neanderthal population collapsed completely.

Future research and model improvements

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.

More information: Yaping Shao et al, Pathways at the Iberian crossroads: Dynamic modeling of the middle–upper paleolithic transition, PLOS One (2025). DOI: 10.1371/journal.pone.0339184

Citation: Simulations explore Neanderthal and modern human encounters in ancient Europe (2025, December 22) retrieved 22 December 2025 from https://phys.org/news/2025-12-simulations-explore-neanderthal-modern-human.html

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