High-resolution ecosystem changes pacing the millennial climate variability at the Middle to Upper Paleolithic transition in NE-Italy.

Observation of high-resolution terrestrial palaeoecological series can decipher relationships between past climate flips, their effects on ecosystems and wildfire cyclicity. Here we present a new radiocarbon dated record from Lake Fimon (NE-Italy) covering the 60-27 ka interval. Palynological, charcoal fragments and sediment lithology analysis were carried out at a centennial to sub-centennial resolution. Identification of the best modern analogues for MIS 3 ecosystems further enabled to thoroughly reconstruct vegetation structure changes through time. This series also represents an "off-site" reference record for chronologically well-constrained Palaeolithic sites documenting Neanderthal and Homo sapiens occupations in the same region. Neanderthals lived in a mosaic of grasslands and woodlands, composed of a mixture of boreal and broad-leaved temperate trees analogous to those of the modern Central-Eastern Europe, the Southern Urals and central-southern Siberia. Dry and other grassland types expanded steadily from 44-43 ka and peaked between 42-39 ka, i.e., about the same time when Sapiens reached this region. This vegetation, which finds very few reliable modern analogues in the adopted Eurasian calibration set, leads to the expansion of ecosystems able to sustain large herds of herbivores. During 39-27 ka, the landscape was covered by steppe, desert-steppe and open dry boreal forests similar to those of the modern Altai-Sayan region. Both Neanderthal and Sapiens lived in contexts of expanded fire-prone ecosystems modulated by the high-frequency climatic cycles of MIS 3.