The answer is that before 1500, human beings basically lived in isolated areas. In fact, all ethnic groups are scattered all over the country in a completely isolated way. It was not until around 1500 that there was direct communication between ethnic groups for the first time. From then on, they finally came together, whether it was the South African Bushmen, the educated China officials or the primitive patagonians.
So 1500 is an important turning point in human history. We can compare Columbus with astronauts: the former arrived in San Salvador, breaking the shackles of regional isolation; The latter landed on the moon, breaking the shackles of planetary separation.
In fact, strictly speaking, world history began with Columbus, Da Gama and Magellan's voyages to the Western Ocean. Before that, there was only a relatively parallel history of all ethnic groups, but there was no unified human history. If the monism about the origin of human beings is correct, then at the beginning of human history, there is a unified or * * * same origin. However, in the long paleolithic period of millions of years, human beings gradually dispersed to most of the land on the surface of the earth. Later, the end of the ice age raised the sea level of the ocean, thus separating Africa from Europe, North and South America from Northeast Asia, and Australia from Southeast Asia-just to mention a few major separations.
Since then, human beings have lived in different degrees of geographical isolation. Some people have been completely isolated, such as the aborigines in Australia, which is a good example. From their last migration from Southeast Asia to james cook, the captain arrived in Australia, and they had no contact with the outside world for more than 3,000 years. Residents of North America and South America are almost isolated from the world. The last group of them crossed the sea from Siberia to America about 10o 00 years before Columbus sailed. Later, although Norwegian expeditions had reached the northeast coast of North America and Polynesians might have reached South America, they did not have any lasting influence on Indian residents. About 6000 years ago, sub-Saharan Africa was also isolated to a considerable extent, because the Sahara desert had become very dry at that time, which became a huge obstacle to prevent people from moving. However, in fact, the contact between African blacks and the outside world is still limited and intermittent. Mainly because of these connections, they enjoy advantages that some American Indians and Australian aborigines do not have. Sailors in Southeast Asia brought sweet potatoes and bananas, Middle Easterners brought the technology of mining, smelting and forging iron, while Arabs spread their civilization and religion to blacks from bases in North Africa and East Africa. These and other advances have enabled blacks to develop natural resources more effectively and produce food in large quantities.
The rest of the world includes Europe, Asia and North Africa. Throughout history, North Africa has been more closely linked with the northern shore of the Mediterranean than with sub-Saharan Africa. For convenience, this continent from Morocco to kamchatka peninsula and from Norway to Malaya can be called Eurasia. It is Eurasia that constitutes the "central zone" of world history. It occupies two fifths of the world's land, including nine tenths of the world's population. It is the birthplace of the earliest and most advanced civilization of mankind. The world history before 1500 years is essentially the history of Eurasia. Only in Eurasia, there is a huge and continuous interaction between various nationalities and civilizations. Although Australian aborigines and American Indians live in a state of complete isolation, and Africans in sub-Saharan Africa live in a state of semi-isolation, for thousands of years, people of mixed European and Asian ancestry.