Northern Hemisphere Glaciation, African climate and human evolution

The hypothesis of a connection between the onset (or intensification) of Northern Hemisphere Glaciation, the stepwise increase in African aridity (and climate variability), and an important mammalian (including hominin) species turnover is a textbook example of the initiation of a scientific idea and its propagation in science. It is, however, also an example of the persistent popularity of a hypothesis despite mounting evidence against it. A critical review of key publications on the topic and statistical re-analysis of key records of global ice volume and African climate leads to three conclusions: (1) The Northern Hemisphere Glaciation was a gradual process occurring between similar to 3.5 and 2.5 Ma, not a single event at similar to 2.8 Ma or at any other time. (2) A consistent stepwise (+/-0.2 Ma) transition toward greater aridity in Africa at similar to 2.8 Ma does not exist; instead, there are regionally different, gradual transitions partly in connection with the intensification of the Northern Hemisphere Glaciation, but above all with the establishment of the tropical Walker Circulation after similar to 2 Ma. (3) Mammalian (including hominin) species turnovers at this time also appear to have been gradual, rather than stepwise. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study evaluates the connection between Northern Hemisphere Glaciation, African climate, and mammalian species turnover, concluding that these events were gradual rather than sudden, contrary to previous hypotheses. The research highlights the importance of re-analyzing key records to challenge existing ideas and establish a more accurate timeline for these environmental changes.