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.

In the Late Middle Paleolithic of Central Europe, two main cultural complexes have been distinguished: the Micoquian or Keilmessergruppe (KMG), and the Mousterian. Their differences mainly consist in the frequence of some retouched tools and the presence of bifacial technology. When these industries coexist, one element of discussion is the application of different concepts to manufacture tools with the same techno-functionality. This is particularly true for backed artifacts, such as Keilmesser (backed, asymmetrical bifacially-shaped knives) opposed to flake-tools equipped with a natural or knapped back. We conducted a techno-functional analysis of the backed tools from the G-Layer-Complex of Sesselfelsgrotte, one of the main Late Middle Paleolithic sequences in Central Europe, characterized by a combination of KMG and Mousterian aspects. In order to better understand the morpho-metrical data, 3D scans were used for recording technical features and performing semi-automatic geometric morphometrics. Results indicate that the techno-functional schemes of Keilmesser show a moderate variability and often overlap with the schemes of other typological groups. Within bifacial backed knives, a process of imitation of unifacial flake tools’ functionaly was recognized particularly in the cutting edge manufacturing. Keilmesser proved to be the long-life, versatile version of backed flake-tools, also due to the recurrent valence as both tool and core. This is why Keilmesser represent an ideal strategic blank when a mobile and multi-functional tool is needed. Based on these data, it is assumed that the relationship between Mousterian and KMG is deeply rooted and the emergence of KMG aspects could be related to constrained situations characterizing the long cold stages of the Early Weichselian. A higher regional mobility caused by the comparably low predictability of resources characterized the subsistence tactics of Neanderthal groups especially at the borders of their overall distribution. For this reason, Keilmesser could have represented an ecological answer before possibly becoming a marker of cultural identity.

The demographic history of Neanderthals is only partially understood. In Europe, some degree of genetic continuity has been shown from 120 thousand years ago (ka) onward despite the occurrence of multiple subsequent diversification events. While it has been proposed that a population turnover preceded the emergence of Late Neanderthals in Europe, the extent, timing, and geographic location of this event are currently unknown. Here, we report ten mitochondrial DNA sequences (mtDNAs) of Neanderthal individuals from six archaeological sites in Belgium, France, Germany and Serbia, and analyze them alongside 49 published mtDNAs. The integration of phylogenetic and molecular dating analyses with an extensive archaeological dataset enabled us to reconstruct temporal and spatial patterns in Neanderthal distribution. Remarkably, nearly all Late Neanderthal individuals across Europe belong to a single mtDNA lineage that diversified recently, confirming a large-scale genetic replacement. Our analyses date this diversification event to approximately 65 ka and suggest that it likely originated from a population refugium in southwestern France from which Neanderthals appear to have undergone a major range dispersal across Europe. In addition, we detect a sharp decline in the Neanderthal mtDNA effective population size beginning ~45 ka and reaching a minimum ~42 ka, shortly before their extinction. This study demonstrates that integrating molecular and archaeological datasets provides a more detailed understanding of the Late Neanderthal population’s history, and highlights the critical role of climate-driven refugia and subsequent range expansions in shaping the genetic landscape of Neanderthals through time.