Climate change in Europe between 90 and 50 kyr BP and Neanderthal territorial habitability

Scandinavian regions, a large part of Eastern Europe, the Alps and part of the Mediterranean coast of the Iberian Peninsula. Other regions undergo changes in probability over time. A more detailed analysis of the characteristic habitability areas shown in these maps is presented in the following section. The northern limit of habitability is not a pure function of latitude–Scandinavian regions have lower scores than Britain at all periods, while southern Europe seems to have been less suitable during early periods and more suitable later. Over time, the percentage of ecological niches suitable to Neanderthals increases in P2 and P4 if we use a probability threshold greater than or equal to 0.8. If we refer to a more stringent probability P (greater than or equal to 0.9), then we obtain a constant increase in P2, a clear decrease in P3 and almost constant values thereafter (see S6 File). We also identify areas where, over time (between P1 and P5), the probability of suitable eco- logical niches has always been very high (0.9% of pixels always present over the periods with a probability greater than 0.8, Fig 7; and 0.1% of pixels with a probability greater than 0.9, Fig 8). Description of each period Period 1 (90–83 kyr BP). In the first period, there was a higher probability of niches suit- able for Neanderthals in the British Isles than for the other periods (Fig 2, the AUC value is 0.940): several pixels show values greater than 0.8 (Fig 9). The North and the West of the Ibe- rian Peninsula, the Italian peninsula, the French and the German regions and the Balkans

seem to have been very suitable regions and some suitable spots were present also in the Mid- dle East and around and between Black and Caspian sea. 2.2% of the total emerged study area seem to have been very suitable for Neanderthals (P > 0.8), a more stringent probability (P > 0.9) suggests 0.4% of niches. Period 2 (83–69 kyr BP). In the second period, the probability of suitable niches in the British Isles decreased compared to P1, but increased in Ireland and Iberia, Western Europe, the Italian peninsula and the Balkans (Fig 3). Our analysis shows an increase of probability in the east, around the Black Sea and in the Middle East (Fig 10). In this period, the percentage of suitable niches for Neanderthals increased and reached high values: 3.3% (P >0.8), and 1.6% for P > 0.9. Period 3 (69–64 kyr BP). During the third period there was an increase in high probabil- ity niches in southern Europe, particularly in the western Iberian Peninsula, while its center and eastern side have very low values (Fig 4). The Italian Peninsula, the Tyrrhenian coast of Fig 2. Heat maps (blue represent lower values (0–0.19), gradually transitioning (range of 0.20) to red, that is the higher values (0.81–1)) of Maxent modelling results: Estimated probability of suitable conditions for the Neanderthals, for period: P1 (90 kyr– 83 kyr). https://doi.org/10.1371/journal.pone.0308690.g002 PLOS ONE Neanderthal habitability PLOS ONE | https://doi.org/10.1371/journal.pone.0308690 February 26, 2025 6 / 17