Additional link: https://qz.com/africa/1996308/what-do-we-know-about-human-evolution/
Part of the answer to the first question may lie in the fact that parts of west Africa appear to have been less affected by the extremes of repeated cycles of climate change. This may have created stable environmental conditions over a long period of time. As a result of such stability, a finely tuned toolkit that had worked well for millennia might not have needed to change, regardless of the social complexity of the people who made the tools.
The answer to the second question lies in the fact that this region of Africa was relatively isolated. To the north, it meets the Sahara Desert and to the east, there are the Central African rainforests, which were often cut off from the west African rainforests during periods of drought. However, around 15,000 years ago, there was a major increase in humidity and forest growth in central and western Africa. This may have linked different areas and provided corridors for dispersal of human populations. This may have spelled the end for humanity’s first and earliest cultural repertoire and initiated a new period of genetic and cultural mixing.
What is clear is that the long-held simple unilinear model of cultural change towards ‘modernity’ is not supported by the evidence. Groups of hunter-gatherers embedded in radically different technological traditions may have occupied neighboring regions of Africa for thousands of years, and sometimes shared the same regions. Long isolated regions, on the other hand, may have been important reservoirs of cultural and genetic diversity. This matches genetic studies and may have been a defining factor in the success of our species. Our findings are a reminder of the dangers of ignoring gaps on the map.
#TimeToFixGapsOnTheMap