Archaeological evidence across the European continent from the end of MIS 5 through MIS 4 suggests that the cooling effects of the latter in the northern hemisphere influenced the Neanderthal population. There is an apparent reduction in the number of sites suggesting population shrinkage or redistribution1. At a regional scale, changes in behaviour have been proposed for Southwestern France, where Neanderthal occupations without fire during MIS 4 have been documented at different sites, motivating a hypothesis on the inability of these Neanderthals to make fire2,3,4. This hypothesis highlights the important role of climate in shaping human behaviour.

To better understand Neanderthal population dynamics and assess the degree of regional behavioural variability during critical conditions of environmental change it is important to seek evidence from the Iberian Peninsula, which has previously been considered as a refugium during cold periods, particularly the south of the peninsula5,6,7,8 and more recently the east coast as well9. Considerable work has been done to establish site-specific palaeoclimatic records for Iberian sites dating to MIS 59,10,11,12,13 and MIS 3, e.g.14,15,16,17,18,19. In contrast, relatively few site-specific records exist for MIS 4 in the peninsula. This potentially hampers our understanding of the local environmental settings in which MIS 4 Neanderthal occupations occurred, as we depend on regional proxy data with coarse resolution.

The Iberian Peninsula is characterised by considerable climatic diversity in which mountainous topography and Atlantic and Mediterranean effects cause local environmental conditions to vary significantly even across relatively short distances20. It should be borne in mind, therefore, that local conditions may not always reflect wider regional trends. Marine records (e.g. MD95-2042) suggest that during MIS 4 the Iberian Peninsula saw the progressive development of semi-desert vegetation in line with a significant decrease in sea-surface temperature (SST)21,22. Palynological records from Abric Romaní in the northeast indicate millennial-scale climatic variability through the course of MIS 4 into MIS 3, characterised by fluctuations between cold and warm phases driving the decline and expansion of arboreal pollen, including deciduous and evergreen Quercus, Olea and more23,24. This corresponds with terrestrial pollen data from Galicia in the northwest of the peninsula, where records for MIS 4 suggest that coniferous taxa are locally rare at this time, and the presence of Erica, Calluna and Poaceae suggests an environment comprised of alternating heath and temperate grasslands25. Meanwhile, evidence from the Tagus Basin in central Iberia interior suggests that episodes of significant loess accumulation during MIS 4 are associated with the development of cold and dry conditions26. On the other hand, palynological data from Bolomor Cave in Valencia points to the existence of a glacial refugium during MIS 6, with closed forests and high plant diversity9. This evidence could predict similar conditions for MIS 4 in the region and hints at a mosaic scenario for the Iberian Peninsula with different econiches shaped by local geographic factors.

Turning to the archaeological record, more Middle Palaeolithic sites in Iberia are dated to MIS 3 than to MIS 5 and MIS 4 (Supplementary Table S1). As a result, there is considerably more bioanthropological, genetic and cultural information on late Neanderthals (younger than 60 Ka). Although there is an apparent reduction of sites when compared with the preceding and subsequent periods, the significantly shorter duration of the MIS 4 period compared to MIS 5 and MIS 3 and the inaccuracy of some of the chronostratigraphic data should be considered.

The chronostratigraphic and archaeological data from Iberian MIS 4 sites is currently insufficient to understand Neanderthal population dynamics and behaviour in relation to the broader European context or to compare different proxies across MIS 5, MIS 4 and MIS 3 at a regional scale. Regarding fire, there is purported evidence of abundant charcoal, burnt sediment and burnt rocks in Navalmaíllo Layer F (central Spain), but this layer could date to late MIS 5 rather than MIS 427. The lithics from various Iberian MIS 4 sites reflect settlement patterns involving small territories, as informed by short-distance raw material procurement27,28,29,30,31 and recurrent occupation of sites32.

The central Mediterranean region of Spain is prominent for its Neanderthal archaeological record. There are several sites in the region featuring deep stratigraphic sequences that span either the entire MIS 5 period, including Cova Negra33 and Bolomor Cave34, or the entire MIS 3 period, such as El Salt35. Based on archaeological evidence from these sites, it appears that Neanderthals in this region had similar adaptations during both time intervals. Faunal assemblages are mostly composed of anthropogenic large and medium-sized ungulates, mainly deer, horse and wild goat, with minor proportions of small-sized animals (tortoise and rabbit) and reflect generalist, broad spectrum hunting traditions resulting from adaptation to biodiverse environments. Overall, the lithic technology from these MIS 5 and MIS 3 sites does not show any significant difference either36,37,38. Broadly, it is characterised by a predominance of recurrent centripetal Levallois (RCL) sequences and discoidal schemes, alongside a lesser representation of other Levallois modalities and non-Levallois technical strategies, such as polyhedral and orthogonal procedures39,40,41,42. This variability, documented throughout MIS 5 and MIS 3 contexts in the region, is possibly related to territorial aspects entailing differential raw material availability and site function determining the use of different activity-specific tools at different sites43,44,45.

Finally, current evidence shows that both MIS 5 and MIS 3 Neanderthals in the central Mediterranean region of Iberia made simple open hearths35,46,47 and wood-gathering patterns appear to be similar irrespective of glacial, interglacial, stadial or interstadial conditions18,48,49.

Focusing on different aspects of behaviour possibly sensitive to changes in climate such as patterns of group mobility, site occupation duration and seasonality, data from the MIS 5 contexts in this region generally suggest that Neanderthals in the region were occupying relatively small territories, as shown by local lithic raw material procurement patterns39,50 and were recurrently occupying sites for short time periods as suggested by tool recycling and diachronic successions of discrete archaeological assemblages in Bolomor Cave39,51. In Cova Negra, presence of carnivores throughout the sequence has been interpreted as evidence for short-term human occupations52 although no geoarchaeological or archaeostratigraphic data is available to corroborate this. For MIS 3, a lithic raw material study for El Salt shows the continued use of a river-bound territory of less than 5 km throughout the entire sequence53,54 and an archaeostratigraphic study of the faunal and lithic record from a segment of the sequence dating to early MIS 3 suggests a pattern of short-term, recurrent occupation of the site55. Leierer et al.56 corroborated this pattern using sedimentary evidence from the fire record and proposed relatively long periods of site abandonment, which could suggest high group mobility. Although these MIS 5 and MIS 3 data are not comparable directly due to their different degrees of temporal resolution, they generally reflect a Neanderthal population consisting of highly mobile groups occupying relatively small territories.

Considering the above-mentioned evidence, filling the gap of information for MIS 4 becomes relevant to: (1) establish the extent of environmental change in the region during MIS 4, and (2) assess the degree of Neanderthal behavioural change (including fire use) from MIS 5 to MIS 3 in a regional context. To this end, here we report archaeological evidence of human occupations with anthropogenic fire and absolute dates from Abric del Pastor, a Middle Palaeolithic rock shelter site in Alcoy, Spain (Fig. 1, Supplementary Fig. S1). The site is undergoing systematic investigation since 2006 and has yielded lithic, faunal and combustion assemblages whose study has provided valuable information regarding Neanderthal settlement dynamics57,58. The archaeological sequence appears to represent a succession of brief Middle Palaeolithic occupation events linked to different subsistence activities and these are all centered around single hearths, which are present throughout the sequence57. Until now, ascribing the site to a MIS 4 chronological framework has been problematic and the in situ nature of the combustion features remained uncertain. A terminus ante quem for the sequence is given by the presence of bone remains of Testudo Hermanni, which diminishes in the regional record by early MIS 359,60. The good states of preservation of the sedimentary deposit, together with weak frost-induced lenticular microstructures observed microscopically57, suggest a generally cool or cold climate but is insufficient evidence to ascribe the sequence to MIS 4. A recent multiproxy study investigating the carbon and hydrogen isotopic values of sedimentary leaf waxes through the sequence (Units I-VI) point to a variable precipitation regime, while cryoturbation features revealed through soil micromorphology indicate generally cool conditions throughout56,61. Based on the anthracological record, the Middle Palaeolithic human occupations are associated with dry/semi-arid supramediterranean conditions (mean annual temperature 8–13 °C and mean annual precipitation 200–600 mm) with juniper stands, heliophilous taxa and scattered cryophilous pine stands48,49.

Figure 1 Location of Abric del Pastor rock shelter. Full size image

Our ongoing investigations at Abric del Pastor are geared at understanding site formation processes and combustion feature formation processes, dissecting archaeological palimpsests and providing a chronostratigraphic context for the Middle Palaeolithic occupations. In this paper, our objectives are threefold: (1) to provide chronometric dates that help establish if the archaeological deposit formed during MIS 5, MIS 4 or MIS3, and (2) to characterize the combustion features and corroborate their nature as anthropogenic combustion structures, and (3) to describe and assess the variability of the lithic, faunal and combustion record within its stratigraphic context.