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In paleoanthropology, the recent African origin of modern humans or the Out of Africa theory (OOA) is the most widely accepted model of the geographic origin and early migration of anatomically modern humans (Homo sapiens). It follows the early expansions of hominins out of Africa, accomplished by Homo erectus and then Homo neanderthalensis.
The model proposes a single origin of Homo sapiens in the taxonomic sense, precluding parallel evolution in other regions of traits considered anatomically modern, but not precluding multiple admixture between H. sapiens and archaic humans in Europe and Asia.
H. sapiens most likely developed in the Horn of Africa between 300,000 and 200,000 years ago, although an alternative hypothesis argues that diverse morphological features of H. sapiens appeared locally in different parts of Africa and converged due to gene flow between different populations within the same period. The recent African origin model proposes that all modern non-African populations are substantially descended from populations of H. sapiens that left Africa after that time.
There were at least several out-of-Africa dispersals of modern humans, possibly beginning as early as 270,000 years ago, including 215,000 years ago to at least Greece, and certainly via northern Africa and the Arabian Peninsula about 130,000 to 115,000 years ago. There is evidence that modern humans had reached China around 80,000 years ago. Practically all of these early waves seem to have gone extinct or retreated back, and present-day humans outside Africa descend mainly from a single expansion about 70,000-50,000 years ago, via the so-called Southern Route. These humans spread rapidly along the coast of Asia and reached Australia by around 65,000-50,000 years ago, (though some researchers question the earlier Australian dates and place the arrival of humans there at 50,000 years ago at earliest, while others have suggested that these first settlers of Australia may represent an older wave before the more significant out of Africa migration and thus not necessarily be ancestral to the region's later inhabitants) while Europe was populated by an early offshoot which settled the Near East and Europe less than 55,000 years ago.
More information: Science Daily
In the 2010s, studies in population genetics uncovered evidence of interbreeding that occurred between H. sapiens and archaic humans in Eurasia, Oceania and Africa, indicating that modern population groups, while mostly derived from early H. sapiens, are to a lesser extent also descended from regional variants of archaic humans.
Recent African origin, or Out of Africa II, refers to the migration of anatomically modern humans (Homo sapiens) out of Africa after their emergence at c. 300,000 to 200,000 years ago, in contrast to Out of Africa I, which refers to the migration of archaic humans from Africa to Eurasia from before 1.8 and up to 0.5 million years ago. Omo-Kibish I (Omo I) from southern Ethiopia is the oldest anatomically modern Homo sapiens skeleton currently known (around 233,000 years old). There are even older Homo sapiens fossils from Jebel Irhoud in Morocco which exhibit a mixture of modern and archaic features at around 315,000 years old.
Since the beginning of the 21st century, the picture of recent single-origin migrations has become significantly more complex, due to the discovery of modern-archaic admixture and the increasing evidence that the recent out-of-Africa migration took place in waves over a long time. As of 2010, there were two main accepted dispersal routes for the out-of-Africa migration of early anatomically modern humans, the Northern Route (via Nile Valley and Sinai) and the Southern Route via the Bab-el-Mandeb strait.
Fossil evidence also points to an early Homo sapiens migration with the oldest known fossil coming from Apidima Cave in Greece and dated at 210,000 years ago. Finds at Misliya cave, which include a partial jawbone with eight teeth, have been dated to around 185,000 years ago. Layers dating from between 250,000 and 140,000 years ago in the same cave contained tools of the Levallois type which could put the date of the first migration even earlier if the tools can be associated with the modern human jawbone finds.
An eastward dispersal from Northeast Africa to Arabia 150,000-130,000 years ago is based on the stone tools finds at Jebel Faya dated to 127,000 years ago (discovered in 2011), although fossil evidence in the area is significantly later at 85,000 years ago. Possibly related to this wave are the finds from Zhirendong cave, Southern China, dated to more than 100,000 years ago. Other evidence of modern human presence in China has been dated to 80,000 years ago.
The most significant out of Africa dispersal took place around 50,000-70,000 years ago via the so-called Southern Route, either before or after the Toba event, which happened between 69,000 and 77,000 years ago. This dispersal followed the southern coastline of Asia and reached Australia around 65,000-50,000 years ago or according to some research, by 50,000 years ago at earliest. Western Asia was re-occupied by a different derivation from this wave around 50,000 years ago and Europe was populated from Western Asia beginning around 43,000 years ago.
Beginning 135,000 years ago, tropical Africa experienced megadroughts which drove humans from the land and towards the sea shores, and forced them to cross over to other continents.
By some 50-70,000 years ago, a subset of the bearers of mitochondrial haplogroup L3 migrated from East Africa into the Near East. It has been estimated that from a population of 2,000 to 5,000 individuals in Africa, only a small group, possibly as few as 150 to 1,000 people, crossed the Red Sea. The group that crossed the Red Sea travelled along the coastal route around Arabia and the Persian Plateau to India, which appears to have been the first major settling point.
The dating of the Southern Dispersal is a matter of dispute. It may have happened either pre- or post-Toba, a catastrophic volcanic eruption that took place between 69,000 and 77,000 years ago at the site of present-day Lake Toba in Sumatra, Indonesia.
More information: The Guardian
I got interested in palaeontology and vertebrate history
-sparked by books on human evolution
-then vertebrate evolution.
Studying with palaeontologists kindled
my interest in fieldwork.
Greg Graffin
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