| Summary: | According to the "Out-of-Africa 2" theory of human evolution all living humans today descend from a group of Anatomically Modern Homo sapiens or Anatomically Modem Humans that evolved in Africa 200,000 years ago and subsequently migrated out of Africa and spread into the rest of the World around 100,000 years. As a result an interest has developed in establishing a concrete theory of the factors that compelled and/or motivated our ancestors to venture out of their African origins at this time. Interestingly, the Earth's Last Glacial Cycle also dates from this period--stretching from 115,000 to 10,000 years ago. Current paleoclimate evidence suggests that the climatic repercussions of this glacial cycle in Africa resulted in a shift towards a drier and somewhat cooler climate state and the fragmentation of the formerly extensive forested African landscape. As a result, theories of early human migration have cited African climate change during the late Pleistocene as a determinant; however, the mechanisms responsible for the development of hyper-arid conditions in Africa at this time have remained unresolved. Although, past global climate change has been ascribed to changes in radiative forcing and changes in atmospheric carbon dioxide, recent paleoclimate studies have revealed that African climate is sensitive to changes in SSTs in the Atlantic, as it appears that subtropical Africa was more arid when North Atlantic sea surface temperatures (SSTs) were cold during glacial periods. The forcing mechanism believed to be responsible for the development of these cold SSTs are the so-called Heinrich Events that are documented as massive surges of icebergs (from high-latitude ice sheets) into the North Atlantic Ocean during high-latitude glaciations. These Heinrich events resulted in the release of large quantities of freshwater into the North Atlantic, which in turn led to a weakening on the global ocean thermohaline circulation and widespread cooling throughout the region. In particular, marine sediment records from ...
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