Scientists at the University of Wisconsin in Madison (USA) have discovered one of the key reasons for the dispersal of people on Earth and the emergence of human civilization. It was the climatic changes caused by the oscillations of the Earth's axis. This was announced in a press release on Phys.org.
Researchers have tracked climate and vegetation changes in Africa, Arabia and the Mediterranean over the past 140,000 years. The paper describes a dynamic model that shows when regions were wetter or drier and vegetation cover provided migration corridors for people.
The model shows that about 125,000 years ago, there was an increase in the summer monsoon rainfall in northern Africa and the Arabian Peninsula. This led to a decrease in the area of the deserts of the Sahara and Arabia due to the expansion of pastures. In the Mediterranean and the Levant (an area that includes Syria, Lebanon, Jordan, Israel and Palestine), winter precipitation also increased.
These changes are due to the position of the Earth relative to the Sun. The northern hemisphere was closer to the sun in summer than the southern one, and farther in winter. This contributed to warm, humid summers and cold winters.
About 70-15 thousand years ago, there was an ice age on Earth, while the presence of ice sheets intensified winter Mediterranean storms and led to a drier climate and shrinking ice sheets near the equator. This facilitated the migration of settling people to humid areas with a large number of plants.