Communicating the Story of Climate and Man Tony Ramsay
Forest Fawr Geopark, Brecon Beacons National Park Authority and School of Earth Ocean and Planetary Science, Cardiff University, tonhel@btinternet.com.
From the beginning the story of humans and their primate ancestors was closely related with global climate change. The earliest primates, including lemurs, tarsiers and monkeys appeared and evolved in the warm, wet and forested world which existed between 65 and 10 million years ago. The marked cooling and drying of the Earth’s climate from approximately 9 million years coincided with the near-synchronous expansion of savannah grasslands (Fig. 1) in different geographical locations (Osborne & Beerling, 2005). The progressive expansion of Africa’s grasslands favoured the evolution of hominids leading to the emergence of the genus Homo at approximately 1.99 million years ago.
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Figure 1. Typical savannah vegetation in the Masai Mara Game Park, Kenya. Photo Steven Ramsay.
With the onset of significant global cooling 2.6 million years ago, the African savannah expanded and contracted inversely with repeated glacial and interglacial cycles (Osborne & Beerling, 2005). The emergence of new, more successful human species appears to coincide with glacial intervals.
Figure 2. Ranges of species assigned to the genus Homo (Sarmiento et al., 2007) and suggested times for their migration out of Africa (Oppenheimer, 2003) compared with a composite marine record for Oxygen 18 (0 -2.5 million years) derived by averaging data from the Ocean Drilling Project (Corfield, 2003). The Oxygen 18 record is a proxy for global ice volume changes.