Where did humans come from? Do all the different races in the world really originate from Africa?

The most popular view now is that human beings originated in Africa. But I just can't make myself accept it. The theory that human beings originated in Africa is that the first ancestor of human beings appeared in Africa about 200,000 years ago. About 70,000 to 50,000 years ago, about 200 Africans started to leave for Europe, Asia and America. My first question is about 200 African immigrants. I wonder how long it will take them to come to China. Because they came to China for no purpose, it is only under some accidental circumstances or natural conditions that it is possible to explore China.

Let's imagine starting with 200 Africans who arrived in Arabia. Their first problem is survival. If they can survive in Arabia, they won't move to other places. Of course, unless the quantity is too large, local resources cannot support it. Let's see, what's their average age? According to the discovery of Beijingers, the average age of these 200 people is about 15 years old. Even if the intelligence of these 200 people is slightly higher than that of Beijingers and their average age is slightly higher, even if they are 20 years old, so what? How fast is their population growing? Africa's population growth rate is only 2%. The migration direction of these Africans also needs to be considered. It doesn't point directly to China, but it may be in four directions.

There are so many mountains and rivers on the way to China. Will it really be smooth sailing? This is conquest. Along the way, these Africans may meet local Homo erectus and have a fight. Will the conquest go smoothly? For example, in the war between Africans who landed in Chinese mainland and Homo erectus in China, these Africans may sweep across Chinese mainland like storm clouds? The ancestors of China people seem to belong to the northern Mongols. It is said that during the Ice Age 40,000 years ago, most parts of the northern hemisphere were still covered by huge glaciers. How easy was it to come to China and conquer China? I remember that in Europe, a close neighbor of Africa, there was also an ancient human species, Neanderthals, who lived 17000 years ago.

It is very difficult for Africa to deal with Neanderthals, so the ancestors of China people, thousands of miles away across the mountain, won't live 10 thousand years longer than Neanderthals, will they? Is the genetic theory certain? I don't understand, but I want to know, is the connection between the two inevitable from ancient times to the present? Is it unique? About reproductive isolation. People in the world, all kinds of people, can reproduce with each other, which is not the evidence of unique ancestors. Just like today, pigs, horses, cows and sheep from all over the world can cross each other. It is hard to say that bamboo, horses, cattle and sheep are the same ancestor.