The results of the work of an international group of specialists make it possible to understand how the climate of the largest hot desert in the world changed, why it happened and how it influenced the settlement of ancient people in North Africa.
The work was published in the journal Nature Geoscience. It is known that the Sahara turned into a desert about five million years ago. However, after that, relatively short-term changes in humidity were observed there: the Sahara could become savannah, along which large rivers flowed. These phases were repeated many times in the Quaternary period and are considered key to the development of human populations in the past. However, the mechanisms responsible for the reactivation of the now dormant river systems remain very vague.
To fill this gap, scientists from the German Research Center for Geosciences, the University of Leipzig (Germany), the University of Hawaii (USA) and Pusan National University (South Korea) have reconstructed the climate of the Sahara over the past 160,000 years. The work is based on the analysis of terrestrial and marine sediments in the Gulf of Sidra, or Big Sirte (coast of Libya).
To collect samples, the scientists used the so-called piston coring method, which made it possible to extract nine-meter "cylinders" of silt from the seabed. They contain the remains of sediments and plants transported from the shores of the African continent, as well as shells of microorganisms that lived on the seabed thousands of years ago.
By combining the analysis of these data with the results of computer modeling, it was possible to determine exactly what climatic processes took place in the Sahara over the past 160 thousand years. Experts found that the alternation of wet and dry climatic phases in this region was facilitated by small changes in the Earth's orbit, as well as a decrease and increase in the area of polar ice sheets.
At one time there was a large amount of precipitation, at another - there was no rain at all. Scientists suggest that for the ancient people who lived in the Sahara at that time, these climate fluctuations played a large role, potentially accelerating the settlement of North Africa.