Different views exist on the pattern of Middle Pleistocene evolution in Africa. Some favor a splitting into two or more species, for example, Homo heidelbergensis, Homo helmei, and Homo sapiens, whereas others see evidence for a continuously evolving lineage of only one chronospecies, Homo sapiens sensu lato. This latter view then considers the one chronospecies to be separated further into several subspecies, grades, steps, paleo-demes or other entities. The question is, which of these diverse perspectives is best supported by the current evidence? There is also some disagreement about the geographic pattern of the anatomical modernization process. Although there is clear evidence that northern, eastern, and southern Africa were involved, it appears difficult to assess the distinct roles of the different regions within this long-term process. Interregional migration, for example, during periods of a “green Sahara” might have led to complex patterns.
Bräuer, G. (2012). Middle Pleistocene Diversity in Africa and the Origin of Modern Humans. In Vertebrate Paleobiology and Paleoanthropology (pp. 221–240). Springer. https://doi.org/10.1007/978-94-007-2929-2_15