Significance Neanderthals once inhabited Europe and western Asia, spreading as far east as the Altai Mountains in southern Siberia, but the geographical origin and time of arrival of the Altai populations remain unresolved. Excavations at Chagyrskaya Cave in the Altai foothills have yielded 90,000 stone artifacts, numerous bone tools, 74 Neanderthal fossils, and animal and plant remains recovered from 59,000- to 49,000-year-old deposits. The Chagyrskaya Neanderthals made distinctive stone tools that closely resemble Micoquian artifacts from eastern Europe, whereas other Altai sites occupied by earlier Neanderthal populations lack such artifacts. This suggests at least two dispersals of Neanderthals into southern Siberia, with the likely ancestral homeland of the Chagyrskaya toolmakers located 3,000 to 4,000 kilometers to the west, in eastern Europe.

Abstract Neanderthals were once widespread across Europe and western Asia. They also penetrated into the Altai Mountains of southern Siberia, but the geographical origin of these populations and the timing of their dispersal have remained elusive. Here we describe an archaeological assemblage from Chagyrskaya Cave, situated in the Altai foothills, where around 90,000 Middle Paleolithic artifacts and 74 Neanderthal remains have been recovered from deposits dating to between 59 and 49 thousand years ago (age range at 95.4% probability). Environmental reconstructions suggest that the Chagyrskaya hominins were adapted to the dry steppe and hunted bison. Their distinctive toolkit closely resembles Micoquian assemblages from central and eastern Europe, including the northern Caucasus, more than 3,000 kilometers to the west of Chagyrskaya Cave. At other Altai sites, evidence of earlier Neanderthal populations lacking associated Micoquian-like artifacts implies two or more Neanderthal incursions into this region. We identify eastern Europe as the most probable ancestral source region for the Chagyrskaya toolmakers, supported by DNA results linking the Neanderthal remains with populations in northern Croatia and the northern Caucasus, and providing a rare example of a long-distance, intercontinental population movement associated with a distinctive Paleolithic toolkit.

The period of existence of Neanderthals, their geographical range, and the timing of their dispersal and extinction are key issues in the study of human evolution and migration. Most Neanderthal remains and associated artifacts have been reported from Europe and western Asia, where they range in age from about 430,000 to 40,000 years ago (kiloannus, or ka) (1, 2). Further east, the unequivocal presence of Neanderthals prior to the last interglacial (which began around 130 ka) until about 50 ka is based on hominin remains (3) and DNA analyses of skeletal remains and sediments at three caves (Okladnikov, Denisova, and Chagyrskaya) in the Altai Mountains of southern Siberia (4⇓⇓–7). Additional evidence is required to support suggestions that Neanderthals had reached eastern and northern China by 125 to 105 and 45 ka, respectively (8, 9). Two genetically distinct Neanderthal populations inhabited the Altai region sometime during the Late Pleistocene (10), but the geographical origin of these populations and the timing of their migrations into the region remain unclear. On current evidence, Neanderthals were present at Denisova Cave between about 200 and 100 ka (11, 12).

Chagyrskaya Cave (51°26′34.6′′ N, 83°09′18.0′′ E) is situated 19 m above the Charysh River in the western piedmont of the Altai Mountains (Fig. 1 and SI Appendix, Fig. S1), approximately 100 km west of Denisova Cave (13). The cave consists of two chambers, with a stratigraphic sequence up to 3.5 m thick (SI Appendix, sections S1 and S2, Figs. S2–S4, and Table S1). The dense basal deposit (layer 7) is archaeologically sterile and composed mainly of gravel and fine-grained sediments. An erosional contact (unconformity) separates it from overlying layers 6 and 5, which consist of poorly sorted sediments that contain approximately 90,000 Middle Paleolithic (MP) artifacts (including numerous bone tools), 74 Neanderthal specimens, about 250,000 animal fossils, and a range of plant remains (SI Appendix, section S3) (14 and 15). The sequence is capped by Bronze Age deposits, with no evidence of Upper Paleolithic (UP) occupation.

Fig. 1. Chagyrskaya Cave. (A) Site location in the Altai region of southern Siberia. (B) View of the cave entrance, which faces north. (C) Plan of the cave interior showing the excavated area (in blue). (D and E) Stratigraphic profiles along the two transects (A–A′ and B–B′, respectively) shown in C.

Discussion The Chagyrskaya assemblage and the European Micoquian technocomplex overlap chronologically between about 59 and 49 ka and have strong technological and morphological similarities. The Chagyrskaya assemblage can therefore be viewed as a southern Siberian variant of the European Micoquian, and the Sibiryachikha variant seen more broadly as an expression of Micoquian variability across Eurasia. Micoquian populations are commonly considered specialized horse and bison hunters, adapted to steppe and piedmont environments (27, 28). We attribute their presence in the Altai to the eastward migration of Neanderthals from eastern Europe along the Eurasian steppe belt during the cold and arid conditions of MIS 4 (SI Appendix, section S9). DNA recovered from human remains and sediments indicates that Neanderthals first appeared in the Altai before or during MIS 5 (4⇓⇓–7, 10⇓–12). These early populations are not associated with Micoquian artifacts, which appear at Chagyrskaya only toward the end of MIS 4 or the start of MIS 3. It is not possible to distinguish Neanderthal from Denisovan technocomplexes in the cultural sequence at Denisova Cave due to the homogeneous technological and typological characteristics of the lithic assemblages (20). However, the absence of Micoquian-like artifacts at Denisova Cave in deposits dated to between 59 and 49 ka (11) indicates that Denisova and Chagyrskaya Caves were occupied by two distinct Neanderthal populations, most likely at different times given current evidence that Neanderthals were present at Denisova Cave much earlier than at Chagyrskaya Cave (11, 12). Genetic data from Denisova Cave have also revealed several episodes of gene flow between Neanderthals and modern humans (5, 6) and two different Neanderthal components in Denisova 11, the Neanderthal-Denisovan offspring (SI Appendix, section S5 and ref. 10). We therefore propose that Neanderthals entered southern Siberia on at least two separate occasions, with the most recent incursion originating in eastern Europe and the northern Caucasus, which lie 3,000 to 4,000 kilometers to the west of Chagyrskaya Cave. The identification of Micoquian assemblages in all three regions is consistent with the genetic similarities between Neanderthal remains at Chagyrskaya, Vindija, and Mezmaiskaya Caves (16, 17). Our archaeological data support a rarely observed case of long-distance demic dispersal in the Paleolithic and illustrate that artifacts are culturally informative markers of ancient population movements.

Materials and Methods Stratigraphy and Site Formation. The sedimentary sequence was divided into stratigraphic units—called layers (e.g., layer 6), which were further divided into subunits (e.g., subunit 6c) and sublayers (e.g., sublayer 6c/1)—based on lithological differences and the presence of erosional features. We adopted the stratigraphic scheme used by earlier excavations (13), with further development based on new observations (SI Appendix, section S1). Micromorphological analysis of 10 thin sections (prepared from blocks of undisturbed sediment) was used to elucidate the processes responsible for site formation and depositional and postdepositional environments, and to provide context for the archaeological finds (SI Appendix, section S2). Sample locations were chosen to maximize the potential for interpreting environmental signals, but were restricted to the stratigraphic profiles exposed in 2014 and 2017. Radiocarbon Dating of Bone Collagen. Twenty Bison bone samples retrieved from layers 5 and 6, including at least 10 humanly modified bones from subunit 6b and sublayer 6c/1, were selected for radiocarbon dating. Collagen was extracted from these samples and the >30-kDa fraction isolated by ultrafiltration to remove contaminants with lower molecular weights (15). The extent of collagen preservation was assessed from measurements of collagen yields, stable isotope ratios, and carbon-to-nitrogen (C:N) atomic ratios. Samples were graphitized and their radiocarbon contents measured by accelerator mass spectrometry. The measured ages were considered reliable only if the bones contained more than 1% weight collagen and had C:N ratios between 2.9 and 3.5. For samples that yielded finite conventional ages, calendar-year ages (and the corresponding 68.2% and 95.4% confidence intervals) were estimated using the IntCal13 calibration dataset (SI Appendix, section S4). Optical Dating of Sediments. Twenty-seven sediment samples were collected from layers 5, 6, and 7 for optical dating (34, 35). For most of these samples (23 from layers 5 and 6, and 2 from layer 7), the equivalent dose values were estimated from measurements of the infrared stimulated luminescence signals emitted by individual sand-sized grains of potassium-rich feldspar. Each single-grain dose distribution was examined for any patterns in the data, the coefficient of variation was calculated, and the finite mixture model or central age model was used, as appropriate, to obtain the final dose value for age determination. The equivalent doses of the two other samples from layer 7 were determined using a multiple-aliquot infrared stimulated luminescence procedure. The external environmental dose rate for each sample was estimated from measurements of the beta and gamma emissions from uranium-238, uranium-235, and thorium-232 (and their decay products) and potassium-40, and the small contribution from cosmic rays. Beta dose rates (including the contribution from the decay of potassium-40 and rubidium-87 inside the grains) were determined from laboratory measurements, whereas the gamma dose rate was measured in situ at each sample location. The external dose rate components were adjusted for water content and the optical ages calculated directly in calendar years. Sample collection, preparation, measurement, and data analysis procedures followed those used for optical dating of sediments from Denisova Cave (11, 12), with additional details given in ref. 36 and SI Appendix, section S4. Artifact Technology and Typology. The technological and typological characteristics of the Chagyrskaya artifacts are based on detailed studies of the lithic assemblage from sublayer 6c/1 (SI Appendix, section S6). Typological studies of the Crimean Micoquian collections and European Micoquian artifacts from Sesselfelsgrotte (Germany) were made by author V.P.C. The central Asian Levallois-Mousterian assemblages came from published sources (SI Appendix, section S7), as did the assemblages from Antonovka I and II and Barakaevskaya Cave (SI Appendix, section S8). We incorporated Gladilin’s typology (37) into the attributive analysis of the Chagyrskaya assemblage to account for the typological variability and methods used to work the raw materials. Key attributes included ratios of categorized lithic artifacts, characteristics of primary knapping, core-reduction models, bifacial production, and degree of raw material reduction. The characteristic feature of this method is the analysis of each artifact as a set of technologically significant and multiple, interrelated morphometric characteristics. We studied bifacial tools using scar pattern analysis to reconstruct the sequence of biface manufacture from the existing negatives on the biface. Statistical Analysis of Lithic Assemblages. SPSS Statistics software (v.18) and the PAST program were used for hierarchical cluster analysis, nonmetric multidimensional scaling (nmMDS), and principal component analysis (PCA). Hierarchical agglomerative clustering was accomplished using the centroid linkage method with squared Euclidean distance, which computes the dissimilarity between the centroids of several clusters. nmMDS is a nonparametric ordination method that computes a similarity/distance matrix for a set of items and locates each item in low-dimensional space. PCA provides a composite view of the variability among technological and typological assemblages. All data used for nmMDS and PCA were scaled using z-score standardization. PERMANOVA, a nonparametric multivariate statistical test, was used to compare groups of items and to assess which variables have the greatest influence. Further details of statistical methods are given in SI Appendix, sections S7 and S8. Geometric Morphometric Shape Analysis. A quantitative description of shape variability within and between groups of bifaces from Chagyrskaya Cave and Sesselfelsgrotte (the key Micoquian site in central Europe) was created using the Artifact GeoMorph Toolbox 3-D (AGMT3-D) software package for landmarks-based geometric morphometric shape analysis (38).

Acknowledgments We thank L. Grossman, G. Herzlinger, and O. Echevskaya for geometric morphometric and statistical consultations; S. Shnaider, E. Bocharova, A. Fedorchenko, N. Vavilina, and the entire Chagyrskaya Cave project team for field or laboratory assistance with the archaeological investigations; and Y. Jafari, T. Lachlan, D. Tanner, F. Brink, and V. Vaneev for assistance with optical dating. We acknowledge the support of the Social Sciences and Humanities Research Council of Canada and Microscopy Australia (Centre of Advanced Microscopy, Australian National University) for scientific and technical assistance. The excavation of Chagyrskaya Cave was funded by the Russian Foundation for Basic Research (project 18-09-00041). Analysis of the Chagyrskaya lithic assemblage, including the geometric morphometric and statistical analyses, was funded by the Russian Science Foundation–Deutsche Forschungsgemeinschaft Cooperation (projects 19-48-04107 and UT 41/8-1). Bone tool and scar pattern analysis was funded by the Russian Foundation for Basic Research (projects 18-09-40070 and 19-59-22007). Analysis of the Sesselfelsgrotte lithic assemblage was funded by the Alexander von Humboldt Foundation (Humboldt Research Fellowship for Experienced Researchers, 2016). Geological investigations were funded by the National Science Centre (Poland) (grant 2018/29/B/ST10/00906). Optical dating was funded by the Australian Research Council (fellowships FL130100116, FT140100384, and FT150100138) and an Australian Government Research Training Program Award.

Footnotes Author contributions: K.A.K., S.V.M., and A.P.D. designed research; K.A.K., R.G.R., V.P.C., Z.J., M.T.K., A.V.S., A.I.K., B.L., T.U., S.V.M., M.W.M., K.O., N.A.R., S.T., B.V., and A.P.D. performed research; K.A.K., R.G.R., V.P.C., Z.J., M.T.K., A.V.S., A.I.K., B.L., T.U., M.W.M., K.O., N.A.R., S.T., and B.V. analyzed data; and K.A.K., R.G.R., and M.T.K. wrote the paper.

The authors declare no competing interest.

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