1) The mental growth disorder: The gradual spread of the mental growth disorder among homo species began possibly as long as 3,2 million years ago, but at least 2,5 million years ago. It began as a recessive trait, meaning it was rare and carried only by few individuals. The first stone tools that appeared at that time, indicate this change in the psyche of these individuals.
2) The Bottleneck effect: The mental growth disorder remained relatively small in quantitative terms until the devastating environmental conditions in Africa led to a relative increase in its number in Heidelberg’s population about 120,000 years ago. The huge drought caused by the Ice Age in the northern hemisphere made the normal dominant feature of our genome disappear.
Thus, H. sapiens is not the result of natural selection, but of 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”. This is what seems to have happened in Africa during the Ice Age about +100,000 years ago. The dominant trait/gene disappeared, and the recessive trait/gene became the dominant one. So, this view does not support the hypothesis of multiregional evolution of modern humans.