It is generally believed that the eruption of the Toba volcano more than 70,000 years ago caused the cooling of the global climate and the deterioration of the environment, and eventually led to the extinction of human beings outside tropical Africa. A recent genetic study of living populations suggests that between 60,000 and 50,000 years ago, there was a process in which Africans replaced populations in other regions, and the complete substitution hypothesis holds true about the origin of modern humans. That is, Africans are the direct ancestors of people in other regions.
The statement "From 100000 to 40, 000 years ago, the chain of human evolution in East Asia has never been interrupted" would most question the above researchers' arguments.