There is ample evidence that the Sahara was periodically covered with vegetation in the past by the spread of rivers, lakes, and water-dependent animals such as hippos. These wet periods in North Africa played a crucial role in creating plant corridors outside Africa that allowed various species, including early humans, to spread throughout the world.

From desert to green bush

The results of the research showed that: Periodic wet phases in the Sahara were caused by changes in the Earth’s orbit around the Sun, including precessionbut it did not occur during ice ages.

The scientists modeled the impact of these factors by adding the distant effects of large ice sheets at the high latitudes of the Northern Hemisphere. In fact, they traced the two most visible cycles on the planet: the cyclic transformation of the ice sheet and the cyclic transformation. The transformation of the Sahara Desert into savannah and forest ecosystems reconciles all this with paleoclimatic observations.

These “seasonal contrasts” therefore show a constant periodicity across the seasons. 21,000 years. Changes in precession determine the amount of solar energy received by the Earth at different times of the year, which in turn controls the strength of the African monsoon and the distribution of vegetation across this vast region. The strength of the West African Monsoon System, which causes hotter summers in the Northern Hemisphere, has also increased, resulting in increased precipitation in the Sahara and the spread of vegetation throughout the desert.

The data obtained also shows that: There were no wet periods during the ice ages, when there were large ice sheets that covered much of the high latitudes. This is because these huge ice sheets cool the atmosphere and suppress the expanding tendency of the African monsoon system.

This highlights the important connection between these remote regions. Ice ages over the past 800,000 years influenced the spread of species, including humans, out of Africa.