The Sahara appears
Wind-blown dunes in Chad show the desert is seven million years old, not a few hundred thousand.
- When
- Known to
- ± 500 thousand years
- Era
- Miocene, Cenozoic
Eolian dune deposits found in the northern Chad Basin, in the same beds that yielded Sahelanthropus, are dated to around 7 million years ago — pushing the origin of North African desert conditions back by an order of magnitude from earlier estimates. The likely trigger is the shrinking of the Tethys seaway, which removed a moisture source and altered atmospheric circulation. The Sahara has since oscillated between desert and green savanna on orbital cycles, but the arid state begins here, alongside the earliest hominins.