The Iberian Peninsula documents a long history of Neanderthal evolution. In the northern region early Neanderthals are documented at Sima de los Huesos during Marine Isotope Stage (MIS) 11 or 12 (Arsuaga et al., 2014). In the east, the site of Cova Negra documents Neanderthal presence during MIS 7, up to 273 ka (Richard et al., 2019); and Neanderthal deposits at Bolomor are documented between 400 and 100 ka, during MIS 10 to MIS 5e (Ochando et al., 2019). Some of the latest Neanderthals are documented on the Iberian Peninsula during MIS 3 (Muñiz et al., 2019), when the area served as a climatic refugium during a cold and unstable period (e.g., Daura et al., 2017). There are fewer Middle Paleolithic sites during the intervening time period—MIS 4 and MIS 5; and hominin fossils from this period are even more scarce. Here we describe three new teeth from Axlor Cave that document hominin occupation during this less-well-represented time interval.

The Axlor site is located in a mountainous region in the North Atlantic range of the Iberian Peninsula (Supplementary Online Material [SOM] Fig. S1). It is an open cave in Supraurgonian limestone, at 315 m above sea level, and 30 km from the current coast, in the valley of the Indusi River, a tributary of the Ibaizabal-Nervíón system. Previous publications of the Axlor site have documented skeletal and dental remains recovered from excavations carried out in 1967–1973 (Barandiarán, 1980; Basabe, 1973; Gómez-Olivencia et al., 2020). These remains have been associated in the referenced publications to different levels (III, IV, V and VIII of the nomenclature of levels by Barandiarán, 1980). Different excavation methodologies between current and older excavation campaigns—the latter using arbitrary horizontal levels—make it impossible to establish an equivalence of the stratigraphic charts. The current stratigraphy includes several well-ordered Middle Paleolithic layers (i.e., B to N) dated 50 to 100 ka (Demuro et al., 2023).

In this publication, we describe new human remains from levels N and F (SOM Fig. S1), recovered during the excavation campaigns initiated in 2000 under the direction of J. González-Urquijo. These levels accumulated during MIS 5 and have been dated by optically stimulated luminescence to 99.6 ± 5.8 and 80.0 ± 5.3 ka, respectively. The deposits of Level N, the oldest in the Middle Paleolithic sequence, are up to 40 cm thick. They include a large volume of anthropic contributions and more than 200,000 faunal remains >4 mm. Red Deer (Cervus elephas) is the most abundant species and carnivores are rare. The lithic record is dense, being greater than 20,000 pieces per cubic meter. Most of the lithic industry comprises flint imported from farther than 35 km away, although there are substantial contributions of local quartz and mudstones. Flint tools were produced using Levallois and microLevallois strategies. Most of the retouched tools are sidescrapers; Mousterian points are also present (González-Urquijo et al., 2005, 2014). Level N documents intensive use of fire, with the presence of combustion structures and abundant macrocarbonaceous remains. Most of the fuel is vegetal. Lipid biomarkers indicate that leaves and branches were used for functions other than fuel (Rodríguez de Vera et al., 2020). Burned resin residues are also preserved, the anthropic contribution of which remains to be clarified (Lambrecht et al., 2021).

The younger Level F, which is wedged into the cavity, is between 25 and 40 cm thick. As in Level N, Red Deer is the most abundant species. The archaeological content of Level F is currently under examination, but exotic rocks (e.g., flint) appear to have been used more frequently than in level N, with Mousterian sidescrapers predominating (Lazuen and Gonzalez-Urquijo, 2020).

Having described their archaeological setting, below we describe the new teeth from Axlor and place them in a comparative context vis-à-vis Neanderthals, European Upper Paleolithic (UP) and recent Homo sapiens (hereafter ’recent‘ humans).