Slightly earlier than the fourth century B.C., the fertile green fields of the Sahara began to disappear.

Many large rivers flowed southward into the Niger and eastward into the Nile. From the now dry riverbeds, one can vaguely discern from the barren appearance how the fertile fields began to shrink and disappear.

With some lakes also gone, residents began to move to other places.

1. The Negro people living in Khartoum now have enough evidence to indicate this catastrophic change that took a long time.

Those Negroes who lived in Khartoum during the earliest Stone Age laid much of the foundation for Nile Civilization.

They were already making pots and pots even before the inhabitants of the world-famous earliest city of Iriha. They lived next to a river whose water level during high water was twelve to thirty feet higher than it is now.

These men used a javelin head with a spiked spear made of bone.

Later, a delicate harpoon with three or four barbs and holes in the handle was used.

Across the eerie Sahara we know today, and two thousand miles further west, in some areas of the Azowak Valley, something similar to this harpoon of the Nile River can be found.

Even into the third millennium, large herds of sexual animals were grazing in Lower Nubia.

But now this place is like Aker said: The conditions in the desert today are really miserable.

It would also be difficult for the owner of an ox-drawn water cart to keep one or two animals here year-round.

?2. Sahara has become an important obstacle to human passage. Anyone who travels in this dusty place will notice the traces of the ancient riverbed on the endless sandy fields and rocky plains to the west of the Nile River.

These riverbeds must have brought running water regularly in the past, but now they are as dry as the air above the desert.

The direct cause of this long-standing and continuing drought is not yet known, but it is evident that it is part of a long series of huge events that caused the equator to move south, manipulated the advance and retreat of glaciers, and determined the prehistoric period of violent rains and storms.

part.

In any case, the important point is that about 5,000 or 6,000 years ago, around the time when the Negroes began to migrate and proliferate, and when settled agriculture began in North Africa, the Sahara had become an important obstacle to human passage.

Due to the extension of the Sahara, it has become a barrier for human contact between the north and the south. At the same time, it has also greatly affected the process of human development needs in Africa.

North of this deteriorating desert there were frequent and rarely interrupted contacts between all the developed societies and civilizations of North Africa, the Middle East, and the Mediterranean.

3. Contact between North and South Africa Unfettered migration of populations occasionally occurred on the continent south of the desert.

Thus, Negroes or Negroid species can be found almost everywhere there today.

But the southern and northern parts are becoming increasingly separated.

They go their separate ways and develop their own ways.

But this is just a generalization, and it inevitably has its limitations.

In fact, contact between North and South was never completely severed.

There were routes of plunder, trade and migration from Fezzan to the Niger River, or along the Red Coast and around the eastern Horn of Africa.

Carthage once conducted trade down the west coast, although the Phoenicians were too secretive to allow later generations to know the size of their trade, or how far they advanced.

Horses and vehicles were common in the Sahara for centuries after about 1200 B.C., and later camels.

But the road across the desert is very difficult to confirm, the journey is long and dangerous.

Even riding animals across the Sahara, as the Arabs did in the Middle Ages, along fixed wells one after another, would have taken two months, and many people never reached their destination after setting out.

Of course, this does not mean that without the drying up of the Sahara, human society on the African continent would have developed along the lines of the Mediterranean.

This vast and ever-changing continent always develops, and it can be said that under any circumstances, it develops extremely irregularly and unevenly.

Some ethnic groups developed more than others.

Because the natural conditions of this place may be forests or plains, suitable for healthy highlands and malaria-endemic swamps, some places are rich in plant species and some places are extremely lacking in plant species, these often result in various irregular and unique

type of development.

However, drought in the Sahara played an equally important role in history.

North of the desert, the various civilizations of the Fertile Crescent interacted freely, accumulating invention after invention, and competitor after competitor exerting new pressure on themselves and their neighbors.

In this way, after many centuries, they all entered from the original primitive state to the glorious Bronze Age when religion dominated politics.

This boiling life in the north was only a faint and puzzling echo to the peoples in the southern fringe areas at that time.

The echo disappears and the impact is far away.