The Out of Africa theory is the dominant model of the geographic origin and early migration of anatomically modern humans (Homo sapiens)(a). It arose from discoveries in East Africa less than a century ago. Previously, a more popular idea prevailed which claimed that modern humans arose from different populations of earlier hominids in various regions of the world. This regional development still has some advocates(h)(c).
A 2007 report deviated somewhat from the OoA concept, and suggested that the first Europeans had arrived from Asia, rather than directly from Africa!(f)
While details of the OoA theory are continually being modified in the light of new discoveries, genetic studies have only strengthened support for the theory. The most recent genetic studies suggest that “a vast inland oasis in present-day northern Botswana was once home to the founder population of all modern humans.” (b)
New studies suggest that the early development of homo sapiens may have been more complex than previously thought(e). Chris Stringer, of the Natural History Museum, London, is quoted by The Guardian as saying that “the immediate predecessors of modern humans probably arose in Africa about 500,000 years ago and evolved into separate populations”.
It is still uncertain whether humans left Africa in two or more waves and when did they do so. Stephen Oppenheimer, who has written extensively on the subject, maintains that a single group of migrants were involved, around 80,000 years ago. He offers several papers on the Bradshaw Foundation website(d).>Current opinion favours Bab-el-Mandeb at the south of the Red Sea and the Sinai Peninsula at the northern end, as the most likely exit routes.<
In the September 2021 issue of Nature, evidence was presented that hominins had migrated out of Africa to what was a much greener Arabia, in a series of movements starting approximately 400,000 years ago and later around 300,000, 200,000, 100,000 and 55,000 years ago, coinciding with successive periods of more benign climate on the peninsula(i). Later in the year, another report endorsed the importance of Arabia, describing it as the “cornerstone in early human migrations out of Africa.” This was the conclusion arrived at following the largest-ever study of Arab genomes(j).
As I see it, dating the spread of humans remains unclear to a layman such as myself. Of particular interest is determining more accurately when man first crossed the Bering Strait from Asia into America.
Not directly related to this subject but nevertheless interesting is a recent research report published in the Journal of Mediterranean Archaeology(g) (2021 DOI: 10.1558/jma.18784), which deals with Mediterranean migration trends over 8,000 years. It found that, within the region from about 7,500 BC to AD 500, migration rates ranged from about 6% to 9% of the population within the dataset. These rates seem to have decreased over time and “that despite evidence of cultural connections, there’s little evidence of massive migration across the region.”
A 2021 article in the Smithsonian Magazine reviews recent theories regarding much earlier migrations of hominins, particularly Homo erectus(k).