The arrival of modern humans in Iberia about 40,000 years ago prompted University of Cologne researchers to run simulations combining archaeological and paleoclimate data. Models tested multiple extinction and survival scenarios and found that climate swings severely stressed Neanderthal populations but left a small chance of limited interbreeding. The study estimates roughly a 1% probability of genetic mixing and suggests 2–6% of individuals could carry mixed ancestry, with contact most likely in northwest Iberia.
Did People or Climate Drive Neanderthals to Extinction? Simulations Point to Limited Interbreeding in Northwest Iberia
Cave paintings. Credit: Alicia G. Monedero / Shutterstock.
About 40,000 years ago, groups of anatomically modern humans arrived on the Iberian Peninsula—long thought to be one of the last refuges for Neanderthals in Europe. Exactly what happened next remains debated: did climate change do the lion’s share of the work, or did competition and contact with modern humans hasten Neanderthal decline?
What the Study Did
Researchers at the University of Cologne developed a set of spatially explicit simulations that combined archaeological records of Neanderthal and human occupations with reconstructions of ancient climate. The paleoclimate data—drawn from sources such as peat bogs and marine sediments—helped the team estimate which parts of Iberia were habitable for Neanderthals or modern humans during different time intervals marked by large swings between cold and warm conditions.
Scenarios Modeled
The team ran the model under several plausible scenarios:
- An early, rapid Neanderthal extinction.
- Persistence of small, highly vulnerable Neanderthal populations.
- Longer Neanderthal survival enabling potential contact and interbreeding with incoming humans.
Key Findings
Across all scenarios, climatic fluctuations placed severe stress on Neanderthal populations. Still, the simulations did not rule out limited contact with modern humans. The study estimated roughly a 1% probability that interbreeding occurred on Iberia, and calculated that about 2–6% of individuals across both groups might carry mixed ancestry if such contact happened. The models pointed to northwest Iberia as the most likely region for any such encounters.
Implications
These results suggest climate instability was a major factor in Neanderthal decline on Iberia, while also leaving open a small window for genetic exchange with modern humans. The low estimated probability of interbreeding is consistent with genetic evidence indicating variable levels of admixture across different regions of Eurasia.
What Comes Next
The authors plan to make future simulations more realistic by incorporating ecological variables such as prey availability and more detailed archaeological site data. Adding these layers should improve estimates of habitat suitability and help clarify the timing and likelihood of any interbreeding between surviving modern human lineages and Neanderthals.
Publication: The study’s results were reported in PLOS One. This story was originally featured on Nautilus.
