Soils are known to be products of environmental factors such as climate, vegetation, topographic setting, parent material, and time for formation, so that paleosols, or fossil soils, can potentially reveal changing environments of the past. Evidence from paleosols for past climate and vegetation in East Africa does not support traditional narratives of human evolution during a single transition from primeval forest to dry climate and open grassland. Instead, paleosols indicate climatic oscillations between wet and dry, and alternating expansion of woodland and grassland, since at least 18 Ma (million years ago). Acquisition of dry grassland adaptations such as thick enamel by 18 Ma, adducted hallux by 14 Ma, and cursorial legs by 1.8 Ma, alternated with woodland adaptations such as short stiff back by 16 Ma, erect stance by 6 Ma, and flat face by 3.5 Ma. Our ancestors survived profoundly changing climate and vegetation, with some adaptations lasting only to the next environmental shift, but others proving to be of lasting value.
Retallack, G. (2015)., Paleosols, in W. Henke & I. Tattersall (eds.), Handbook of Paleoanthropology, Dordrecht, Springer, pp. 511-535.
This document is unfortunately not available for download at the moment.