Climatic variability in the Armenian Highlands as the backdrop to hominin population dynamics 50–25 ka

The impact of Late Pleistocene climatic oscillations, volcanism and the diverse terrain of the Armenian Highlands affected hominin population dynamics and movements through the region. To test different scenarios for the period 50–25 ka regarding expansion, adaptive response, intra-population interactions and extinction, we need local on-site paleoclimatic data found in association with hominin occupations. However, this approach has been hampered by the dearth and highly uneven spatiotemporal recovery of paleoclimatic data from prehistoric sites across the region. In this study, we analyze multiple assemblages of fossil micromammals from the Late Middle Paleolithic (LMP) Lusakert-1 rockshelter (two fossil-yielding strata; <55 ka) and Early Upper Paleolithic (EUP) Aghitu-3 Cave (four fossil-yielding strata; ∼39–24 ka) using geometric morphometric-aided taxonomy, to quantify the representation of different species among the abundant and diverse arvicoline genera (Microtus and Chionomys; mean = 58% of assemblages). We combined this approach with quantitative species-level paleoclimatic reconstructions (Bioclimatic Model; 14 rodent taxa) to determine changes in habitat composition as well as temperature and precipitation shifts during the Late Middle–Early Upper Paleolithic. Taphonomic analysis was conducted to establish isotaphonomy among the assemblages. The analysis shows higher than present-day absolute temperatures for the series of occupations at both Lusakert-1 and Aghitu-3, making it unlikely that hominin activity at the sites coincided with extreme cold-climate phases. A multivariate comparison of the taxonomic abundances (genus level) across a wider sample of regional Middle Paleolithic (MP) and Upper Paleolithic (UP) cave sites (Hovk-1, Kudaro-1, Mezmaiskaya, Satsurblia and Dzudzuana) indicates the possibility of cold-period occupation at only two of the sites, Mezmaiskaya Layers 3 and 2 and Kudaro-1 Layer 3. We surmise that the manufacturers of LMP lithic industries in the Caucasus were well adapted to these challenging environments, thus undermining arguments that rapid climate change through the LMP/EUP period could alone have determined the course of population dynamics in this region.