Human Ancestors Dispersal: role of Climate – HADoC

Since apes (hominoid) originated in African tropical forests, 25 Ma ago (Neogene), tectonics has deeply modified the landscape, through continental drift and associated seaway closure/opening (Eastern Tethys, Fram, Central American, etc.), disappearance of the large epicontinental Para-Tethys sea, and uplifts of mountain ranges (African Rift, Andes, Rockies uplifts). Moreover the atmospheric CO2 content variations superimposed on more rapid orbital fluctuations have also largely impacted the human ancestors environmental conditions. To what extent did global and/or regional- scale past environmental changes influence our ancestors' dispersion and radiation through time? It is crucial to test the role of climatic factors on hominoid and hominin evolution on large temporal and spatial scales because climate is often presented as a major trigger of the evolution and dispersal of our ancestors. Although largely debated, this hypothesis has never been directly evaluated. Using the most advanced modeling tools to simulate climate, vegetation and past ecological niches, this project aims at quantifying the impact of climate and environmental changes on ape and hominin distributions through time. To validate numerical simulations, this project builds on an important synthesis of paleontological and paleobotanical data. Our interest will be focused on the “Ape Saga”. Indeed, hominoids took advantage of a brief warming period (the mid-Miocene climate optimum, MMCO, 17-15 Ma), within a long lasting cooling trend covering most of the Neogene to colonize southern Europe, central and finally south-eastern Asia, starting from their initial African cradle. Then, due to the important cooling of the mid to late Miocene, they migrate to reach south-eastern Asia, during the Tortonian. This phase ends during the Tortonian, 7 Ma ago. Starting from here, we will focus only on the African continent and hominin evolution up to the rise of Homo, from 7 Ma to 1.8 Ma—the period during which the last orogenesis of the African Rift occurred, superimposed on large monsoon variations driven by orbital parameters (precession).
By accounting for different forcing factors as tectonics, pCO2 changes and orbital variations, we will be able to compute associated climate and vegetation changes, downscaled to small spatial scales (50 km). This suite of numerical simulations will enable us to characterize the evolution of hominoid and hominin potential niches. From model results and their validation through faunistic and floristic data, we will identify periods during which environmental pressure was determinant, and others during which it was not.
The consortium is made of 4 partners from the French public research sector, which have complementary skills for conducting such a project organized on 4 axes: 1) produce climate and vegetation simulations for the Neogene (CEREGE/LSCE), 2) apply relevant statistical downscaling techniques on these simulations to cope with the spatial scale necessary for ecological niche modelling (CEREGE/LSCE), 3) evaluate ecological niche dynamics and the role of ecology on dispersal events and finally 4) produce new data and compile available faunal and botanical data which are necessary for downscaled climate and vegetation validation (iPHEP/CEREGE). The faunal database (including hominoids and hominins) will be constructed at iPHEP. Our multidisciplinary approach combines both physical (climate, vegetation) and statistical (downscaling, ecological niche) models with faunal and botanical data to quantify the impact of climate and vegetation changes and therefore establish for the first time new consistent scenarios for the dispersion of our ancestors.