Why was the economy in the south of ancient China underdeveloped and the north developed? Only after the Jin Dynasty did a large number of northerners move south? According to the truth, the south is

Why was the economy in the south of ancient China underdeveloped and the north developed? Only after the Jin Dynasty did a large number of northerners move south? According to the truth, the south is easier to survive. There are many Gu Shan in the south, and the plains are mostly swamps and forests. People with severe miasma are more likely to get sick, are not suitable for farming, and often have wild animals, so they cannot feed more people. Due to less precipitation, the forest coverage rate in the north is not as high as that in the south, and the land is relatively soft, such as the Loess Plateau and the Huang-Huai-Hai Plain, which is relatively easy to cultivate, and it is easier to grow wheat and millet to feed a large population. Therefore, before the Jin Dynasty, the south was vast and sparsely populated, while the north was densely populated. With the continuous development of farming civilization, agriculture has been innovated, and productive labor can be widely carried out in the south. Moreover, there has been a war in the north, and only by fleeing to the south can we survive. So after the Jin Dynasty, the south began to catch up with the north.