Human evolution linked to climate change says study

Human evolution linked to climate change says study
Rhett A. Butler, mongabay.com
September 6, 2005

New evidence suggests human evolution was caused by specific periods of climatic change in Africa according to research presented at the Annual Conference of the Royal Geographical Society. These climatic influences played a crucial part in enhancing human development says Dr Mark Maslin, Senior Lecturer in Geography at University College London.

New findings suggest that during the long-term trend of desertification in Africa over the last 2.7 million years, there were clearly identifiable wet and humid periods. According to Dr Maslin, this is the first study to identify the presence of a series of ancient lakes, some more than 100m deep and over 100 square kilometers in size at critical times when humans first appeared.

This research challenges the old and accepted theory that a prolonged period of desertification in Africa initiated human evolution by forcing adaptation to a drier environment. The new theory suggests that humans actually evolved during short periods of great environmental change – when dry periods were punctuated by large rapidly appearing and disappearing lakes. It was these rapid changes in water sources that forced communities to rapidly change and adapt.

“These temporary humid periods would have imposed huge impacts on early humans," says Dr Maslin. "Our research provides strong support for theories in which early human species evolved and spread out in response to a rapidly changing environment.”

Dr Maslin, working with Dr Martin Trauth of the University of Potsdam in Germany, identified these wet and humid periods by the presence of fossilized organic plant and algae life specific to large, deep lake environments. Using isotopic compounds found within the organic layers to date the fossils, three wet periods have been identified at 2.7, 1.9 and 1.1 million years ago. These periods of contrasting climate lasted for approximately 200,000 years.

Evidence shows that during the three wet and humid periods – there was a specific diversification in human evolution. After each period, it was found that the brain size of these early humans increased and became more complex. Dr Maslin argues that this is an indication of adaptation and re-adaptation to the environmental stress caused by appearing and disappearing water sources.

Records show that with the start of a warming period, these water sources could rapidly disappear -- sometimes within a hundred year span. The disappearance of these water sources would have a significant impact on human populations by altering local food sources.

The information in this article is based on a paper released by the Royal Geographical Society.

The Royal Geographical Society

The Royal Geographical Society (with The Institute of British Geographers) is the learned society and professional body representing geography and geographers. It was founded in 1830 and has been one of the most active of the learned societies ever since. It was pivotal in establishing geography as a teaching and research discipline in British universities, and has played a key role in geographical and environmental education ever since. Today the Society is a leading world center for geographical learning - supporting education, teaching, research and scientific expeditions, as well as promoting public understanding and enjoyment of geography.

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