| That is correct: in the field every object that was created by homo sapiens sapiens is counted as a separate artifact. So each flake / discard is also counted - when flint knapping, there will be many such artifacts per finished edge. A more interesting question to ask: Why? But around 10,500 years ago, a sudden burst of monsoon rains over the vast desert transformed the region into habitable land. This opened the door for humans to move into the area, as evidenced by the researcher's 500 new radiocarbon dates of human and animal remains from more than 150 excavation sites. "The climate change at [10,500 years ago] which turned most of the [3.8 million square mile] large Sahara into a savannah-type environment happened within a few hundred years only, certainly within less than 500 years," said study team member Stefan Kroepelin of the University of Cologne in Germany. http://www.livescience.com/4180-sahara-desert-lush-populated... 2006 The findings of this study are that the sedimentological and geochemical properties of the lake sediments confirm that the Sahara has been drying slowly from six thousand years ago to reach the present day conditions around 1,100 years ago,” said lead author Pierre Francus, professor at the National Institute of Scientific Research in Quebec, Canada... Climate scientist Gavin Schmidt, of NASA’s Goddard Institute for Space Studies, explained that around 8,000 years ago, the Earth’s orbit was slightly different to how it is today. The tilt changed from around 24.1 degrees to the present-day 23.5 degrees. http://www.astrobio.net/news-exclusive/how-earths-orbital-sh... So, about 11k years ago the Sahara suddenly burst into life, and about 8k years ago axial tilt changes started the process of removing this burst. The Sahara is also linked to fertility rises in rainforests in South America. |
"The changes in the Earth’s orbital tilt and precession (or the wobbling motion) occur because of gravitational forces emanating from other bodies in the solar system. To understand exactly what happens, picture a spinning top when it is slightly disturbed. Just like a top, the Earth too wobbles slightly about its rotational axis. This tilt changes between roughly 22 and 25 degrees about every 41,000 years, while the precession varies on about a 26,000-year period. These cycles have been determined by astronomers and validated by geologists studying ocean sediment records. "
Are there any recommended references on this 26,000 year cycle?