Climate Zones

The formation of today's climate zones

In the Pliocene period following the Miocene, about 5 to 1.8 million years ago, the climate zones we know today formed on our planet: the tropics, subtropics, temperate zones, and polar regions.

Mammals adapted to the respective climates in all these regions and continued their worldwide triumph. On the African continent, many tropical forests disappeared, and steppes and savannas spread.

Many scientists assume that the spread of the steppes and savannas is connected with the so-called East African Rift Valley. This fault in the earth's crust was probably formed by violent volcanic eruptions in the Miocene about 20 million years ago. The East African Rift Valley extends over a length of about 6000 kilometres from Syria across the Red Sea to the Gulf of Aden.

Research assumes that the East African Rift Valley had a great influence on the spread of steppes and savannahs and was thus instrumental in the development of the upright gait of our ancestors. Over millions of years, the geological activities of the East African Rift Valley not only created the deepest lakes, but also the highest mountains on the African continent.

Due to the mountains running in a north-south direction, clouds and rain could no longer penetrate unhindered into East Africa. The tropical rainforest gave way to dry savannahs due to a lack of moisture. Some monkey species were forced to leave their previous habitat, the trees of tropical primaeval forests, and walk upright. These apes would evolve into the first humans millions of years later.

The current land bridge between South and North America was also formed in the Pliocene. The exchange of species between the northern continent and the South American landmass, isolated for almost 30 million years, is also known as the Great Faunal Interchange.