Diversity and evolution of Quaternary micromammal faunas from South Africa : novel approaches for reconstructing the paleoenvironments of early hominins

Abstract

At the end of the Pliocene and the beginning of the Pleistocene in South Africa, climate changes leading to progressive aridification of the environment favored the establishment of new habitats. This period also corresponds to the emergence of new hominin taxa, suggesting that climatic and environmental changes played a significant role in the morphological and behavioral evolution of the human lineage. The fossiliferous karsts of the 'Cradle of Humankind,' located in the Gauteng province, have provided a rich and well-preserved sequence of fossils that shed light on the evolution of fauna and environments over the past three million years. Among this fossil record, rodents are particularly abundant and serve as excellent paleoenvironmental indicators, providing local climate data complementing other biological and geological proxies. However, the fossil microfauna of the 'Cradle of Humankind' has received limited attention compared to studies on larger mammals. This situation, partly explained by difficulties in identifying species and a lack of ecological data for many taxa, highlights the limitations of traditional paleontological study methods.This thesis explores new approaches for paleoclimatic and paleoenvironmental reconstructions using micromammal remains, combining classical microfaunal analyses with artificial intelligence and geometric morphometric tools. Initially, the bone assemblages of micro- and mesomammals from the Cooper's D and Swartkrans sites were studied with a triple systematic, taphonomic, and paleoecological approach. A biochronology method based on Mystromys molars suggests an age for the microfaunal assemblage of Swartkrans Member 3 prior to the radiometric dates obtained from sediment and bovid teeth. To refine the understanding of climatic conditions during the Pleistocene, a new machine learning-based climate inference method was developed and applied to various African Quaternary assemblages to reconstruct the climatic