The fossil record suggests that at least two major human dispersals occurred across the Eurasian steppe during the Late Pleistocene. Neanderthals and Modern Humans moved eastward into Central Asia, a region intermittently occupied by the enigmatic Denisovans. Genetic data indicates that the Denisovans interbred with Neanderthals near the Altai Mountains (South Siberia) but where and when they met H. sapiens is yet to be determined. Here we present archaeological evidence that document the timing and environmental context of a third long-distance population movement in Central Asia, during a temperate climatic event around 45,000 years ago. The early occurrence of the Initial Upper Palaeolithic, a techno-complex whose sudden appearance coincides with the first occurrence of H. sapiens in the Eurasian steppes, establishes an essential archaeological link between the Siberian Altai and Northwestern China . Such connection between regions provides empirical ground to discuss contacts between local and exogenous populations in Central and Northeast Asia during the Late Pleistocene.

The phenomenon of lithic miniaturization during the Late Pleistocene at times coincided with increased artifact standardization and cutting edge efficiency–likely reflecting the use of small, sharp artifacts as interchangeable inserts for composite cutting tools and hunting weapons. During Marine Isotope Stage 2, Upper Paleolithic toolmakers in northern East Asia specifically used pressure techniques to make small, highly standardized lithic artifacts called microblades. However, little is currently known about how microblades affected the cutting edge efficiency of the toolkits they were a part of. We applied three methods of analyzing cutting edge efficiency to two Upper Paleolithic assemblages recently excavated from Tolbor-17, Mongolia, that document the periods before and after the introduction of microblade technology to the Tolbor Valley. A model incorporating allometric relationships between blank cutting edge length and mass suggests no difference in efficiency between the two periods, while two more conventional approaches both indicate a significant increase. The potential for improved cutting edge efficiency is only observed when the microblade sample is artificially inflated via simulation. Our results highlight challenges related to detecting and interpreting archaeological differences in cutting edge efficiency at the assemblage level.

According to fossil evidence, the Initial Upper Paleolithic (IUP) refers to archaeological assemblages associated with the early dispersal of Homo sapiens across Eurasia. These assemblages are often described as exhibiting a combination of Middle and Upper Paleolithic typo-technological features or, more broadly, as a technology in progression from the former to the latter. Genetic evidence indicates that as members of our species moved across Europe and Asia, they encountered Neanderthal, Denisovan, and possibly other local populations. At the Eurasian scale, the IUP shows considerable variation, but to what extent this corresponds to a relatively unified cultural package strictly associated with our species, or a suite of unrelated technologies reflecting the complex dynamics of a global population turnover, remains unclear. Like most archaeological assemblages, however, the IUP illustrates a combination of adaptive and normative behaviors, along with some stochastic variation. Here, we investigate what drives typo-technological variation within an IUP assemblage to identify traits relevant for larger scale inter-regional comparisons. Specifically, we describe a lithic assemblage dated to ca. 45 ka cal BP from the site of Tolbor-16 in northern Mongolia. We identify three defining aspects of the IUP at the site, namely variation in core shape and size, patterns of blade core reduction, and the presence of Middle Paleolithic typo-technological features. Our goal is to clarify the influence of dynamic reduction processes on assemblage composition and, within the variation observed, to identify typo-technological features that are relevant for inter-regional comparisons and scenarios of population dispersal.