Humans living in North Africa, including what is now the Sahara desert, are thought to have been at the vanguard of the Out of Africa movement, the consensus scenario of human origins. Modern humans, that is. They were ideally placed to enter Europe and western Asia. This fact can actually be turned on its head as North Africa is ideally placed for migration in the opposite direction, from Europe and western Asia into Africa, as happened during the Holocene period.
Still, not to spoil the story at http://archaeologynewsnetwork.blogspot.co.uk/2014/08/early-modern-humans… … and refers to a paper in the journal Quaternary Science Review, that claims that between 130,000 and 75,000 years ago there is evidence of diversity in human culture in North Africa. The period in question is interesting as it is composed of the last interglacial episode and the beginnings of the Ice Age – down to the super volcano that erupted 74,000 years ago (evidenced by a sudden an dramatic downturn in climate). Perhaps the idea is to link this with movement out of North Africa – but the evidence itself appears to mainly involve tool assemblages. Cultural differences, we may guess, are related to differences in tools in use by different groups of people. Four distinct populations have been discovered, they claim (four distinct tool assemblages) each firmly isolated from the others. They also say they were able to take advantage of the rivers and lakes that existed in large tracts of the Sahara at the time. Not only that, groups of people with access to rivers (now dry wadis) were found to have similar tool assemblages – suggesting the same tribal groups were involved. I'm not sure what to make of this as there is a general theory that the desert was there during the last Ice Age – and changes between desertification and a wetter environment involved Milankovitch orbital changes affecting the intensity of the monsoon (and the width of the monsoon band, or track). Are they saying the rivers and lakes were there during the last interglacial – and declined as the world entered the Ice Age. Another line of thought is that in a cooler world, such as the last glacial, sea surface temperatures were lower and therefore there was less precipitation (rainfall) which would agree with the onset of dry conditions and a desert environment.
Oxford University has an ongoing Palaeoclimate Project and the next step is to explore humans in the Arabian peninsular during the same period. It would be interesting to know if they found evidence that rivers and lakes and a generally wet environment existed in the Sahara zone right the way through to 75,000 years ago – or even thereafter.