The mental growth disorder remained relatively small in quantitative terms until the devastating environmental conditions in Africa led to a relative increase in the number in Heidelberg’s population about 120,000 years ago. Then, the massive drought caused by the Ice Age in the northern hemisphere made the dominant feature of our genome disappear.
Thus, H. sapiens is not the result of natural selection but genetic drift. According to general knowledge, “genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation. It can also cause initially rare alleles to become much more frequent and even fixed”. That is what seems to have happened in Africa during the Ice Age about +100,000 years ago. As a result, the dominant trait/gene disappeared, and the recessive trait/gene became the dominant one. So, this view does not support the hypothesis of the multiregional evolution of modern humans.