Climate Science

The Climate of the Apes

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Science  11 May 2012:
Vol. 336, Issue 6082, pp. 651
DOI: 10.1126/science.336.6082.651-c

The middle Miocene, around 15 million years ago, was a crucial time in the evolution of apes and eventually humans. Apes had recently evolved, and as climate warmed, their range expanded greatly, across most of Eurasia, leading to further diversification. One view is that some of these Eurasian apes eventually recolonized Africa as climate later cooled, although the fossil record remains sparse from this period. Hamon et al. explored the climatic conditions that led to this period of warmth in the Miocene and particularly that were favorable for the expansion of subtropical forests that the apes depended on. Using a global climate model, they concluded that the range of forests would be greatest when atmospheric CO2 levels were between about 560 and 700 ppmv. The East Antarctica Ice Sheet, which is thought to have begun to form by the middle Miocene as the overall Cenozoic climate was cooling, but not uniformly, was about 25% of its modern extent. Both conditions are needed to increase precipitation in Europe at that time. Further decreases in atmospheric CO2 levels and the expansion of ice led to the reduction of forests later in the Miocene.

Geology 10.1130/G32990.1 (2012).

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