Pan-African Climate Variability since the Plio-Pleistocene and Possible Implications for Hominin Evolution

Abstract

Three studies were performed in order to ascertain how climate variability in Africa may have influenced the speciation, extinction and dispersals of our early hominin ancestors since the Plio-Pleistocene. δ13C values from fish fossils from a Hominin Sites and Paleolakes Drilling Project Core (HSPDP) from Tugen Hills, Kenya were used to determine that local responses to climate shifts between 3.29 – 2.57 Ma were abrupt enough to limit the habitats of fish in the paleolake. Singular spectral analysis and correlation analysis on five paleoenvironmental records from Africa and one from NE Russia indicate that orbital parameters can explain most of the variance in climate records and that there are far reaching high-latitude teleconnections to African climate. An evolutionary algorithm run on reconstructed time-series from western, eastern and southern Africa allowed for environmental context of hominin evolutionary events to be made. Comparisons between the evolutionary model and the paleoanthropological record showed that during a period of relative stability in eastern Africa, 2.9 – 2.7 Ma, a drastic change in environment at 2.8 Ma would have elicited a response from a population of increased plasticity. This event coincides with a major turnover in the faunal assemblages as well as the first appearance of the genus Homo. New methods were developed in order to aggregate and compare paleorecords of different type and thereby quantify periods of high and low climate variability. Both the Standard Deviation Variability Method and the Accumulated Weighted Rate of Change Variability Method proved valuable in determining environmental variability in and around Africa over the last 400-ka. When the new methods were applied to environmental records and compared to the genetic, archaeological and fossil record, they indicated that the earliest appearance of the MSA occurred during a period of high variability in northern and eastern Africa. Furthermore, these methods showed that migrations within and out of Africa occurred after the source region switched from a period of high variability to a stable environment.