Second, geographical factors. For example, China Han Dynasty was more suitable for farming civilization, while Xiongnu was more suitable for nomadic civilization.

Third, communication problems. More cultural exchanges, including wars, will make these ethnic groups make rapid progress. This is the so-called "born in sorrow, died in happiness." For example, in the Spring and Autumn Period, the so-called "a hundred schools of thought contend" appeared in the wars of various vassal states in China (in fact, there are six schools of thought), which basically laid a cultural foundation for the future development of China society. After the social development in China, until the New Culture Movement when Western learning spread to the east, the classics in the Spring and Autumn Period were basically supplemented and improved except for the invasion of Buddhism. Of course, something is broken.

For another example, in the long-term confrontation between the Han Dynasty and the Xiongnu, both sides absorbed the advantages of the other nation, thus making both nations make great progress. It is wrong and one-sided for mainstream historiography to only emphasize the sinicization of Xiongnu. And the Huns of the Han people. For example, after Zhao Wuling rode and shot in Khufu, the Han people gradually gave up meaningless chariots and began to build cavalry like Huns. This is more obvious in the national integration of Xianbei and Han people.

Fourth, the war of aggression. Africa is the birthplace of human civilization, and the first human civilization-Egyptian civilization was established. At this point, it is hard to say which is earlier, Egyptian civilization or China civilization. Just say what they said before. As a result, Egyptian civilization was completely destroyed by the Romans, and it was not until the19th century that people gradually paid attention to it. The same is true of India. My world history is not very good. I only know that India was invaded by Roman Empire, Mughal Empire and Britain, and there should be other countries. In this way, the present Indian civilization has many external factors. For example, the Taj Mahal has typical Mongolian and Arabic characteristics.

Although the development of America is really slow (I have been to the Mayan Cultural Exhibition, and what they made in the Tang Dynasty may have existed before the Zhou Dynasty in China), it also has its own characteristics, but it was basically destroyed by the arrival of Spanish and Portuguese-led colonists.

Fifth, the resource factor. This is mainly Oceania and Africa. Many island countries in Oceania and Africa have established some powerful countries. They also built like Qin Huang and Wu Han, which led to the shortage of domestic resources, especially trees, and directly led to the country's demise.