The French Middle Gravettian represents an interesting case study for attempting to identify mechanisms behind the typo-technological variability observed in the archaeological record. Associated with the relatively cold and dry environments of GS.5.2 and 5.1, this phase of the Gravettian is characterized by two lithic typo-technical entities (faciès in French): the Noaillian (defined by the presence of Noailles burins) and the Rayssian (identified by the Raysse method of bladelet production).The two faciès have partially overlapping geographic distributions, with the Rayssian having a more northern and restricted geographic extension than the Noaillian. Their chronological relationship, however, is still unclear, and interpretations of their dual presence at many sites within the region of overlap are not yet consensual. Nonetheless, the absence of the Raysse method south of the Garonne River suggests that this valley may have separated two different cultural trajectories for which the Rayssian represents an adaptation to environmental conditions different from those associated with the Noaillian assemblages south of the Garonne River. The aim of this study is to test this hypothesis quantitatively using ecological niche modeling (ENM) methods. We critically evaluate published data to construct inventories of Noaillian and Rayssian archaeological sites. Using ENM methods, we estimate the ecological niches associated with the Middle Gravettian north (Noaillian + Rayssian) and south (Pyrenees Noaillian) of the Garonne River, and these predicted niches are then quantitatively evaluated and compared. Results demonstrate that, despite a relatively large degree of similarity, the niches differ significantly from one another in both geographic and environmental dimensions and that the niche associated with the northern Middle Gravettian is broader than that of the Pyrenees Noaillian. We propose that this pattern reflects different technological, subsistence and mobility strategies linked to the development of the Raysse method in the North, which was likely more advantageous in such environmental contexts than those employed by Pyrenees populations.

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<p>During the Neogene, major tectonics events occurred: uplift of mountain ranges (including the Tibetan Plateau and surrounding regions), opening and closing of seaways, and large variations of atmospheric CO<sub>2</sub> and sea level. What were the consequences of such changes on the dispersal of hominoid populations? We focus on the Miocene to Pliocene time interval (23 Ma-2.6 Ma). First, we analyze the spread of hominoids from their original geographic range, the tropical forests of Africa during the Early Miocene to the first expansion to Eurasia during the mid-Miocene Climate Optimum. Niche modelling combined with paleoclimatic simulations, provides means to circumvent the fragmentary nature of this record. We identify how the large climatic changes during Miocene Transition impact the potential habitats of hominoids and compare our findings to both the related fossil records and paleoenvironmental proxies.</p> <p>Second, we analyze human distribution during the Mid to Late Pliocene (4-3 Ma), i.e. before the triggering of the large perennial Greenland ice sheet, and of huge amplitude northern hemisphere glacial interglacial cycles, while CO<sub>2</sub> evolved between 400 and 300 ppm. In Africa, tropical areas experienced drastic hydrological changes, mainly driven by precession cycles, which deeply modulated monsoon intensity and precipitation patterns, as illustrated by the paleoshore level record of Mega Lake Chad. To explore how orbital parameters strongly modify hydrological cycles over tropical Africa and, the associated dispersion of the genus <em>Australopithecus</em>, we simulated the response of climate, vegetation, and hydrological cycles of the mid to Late Pliocene conditions.</p> <p>For both geological contexts, we provide and analyze a series of Earth System models (IPSL-CM5A2 LR-low resolution-) coupled simulations. Moreover, we associate these fully-coupled simulations with high resolution atmosphere-only model simulations, and a dynamic vegetation model (ORCHIDEE). Both models were used to estimate ecological niches with a spatial resolution of 50 km.</p> <p>We describe the imprint of slow climate changes during the Miocene Climate Transition (MCT) as well as more rapid climate evolution during mid to Late Pliocene, associated with higher frequency oscillation of orbital parameters.</p> <p>This study demonstrates how, for these periods, climate and especially hydrological variations were pivotal to the understanding of hominoid migrations. We compare our findings to fossil records and paleoenvironmental proxy reconstructions.</p> <p>To conclude, we discuss the strengths and limitations of such approaches, which were made possible through a large trans-disciplinary effort between paleontologists, paleoanthropologists, paleoenvironmentalists, paleoclimatologists, and niche modelers.</p>