While the majority view remains that the modern human dispersion Out of Africa was a single event around 60,000+ years ago, it is becoming increasingly likely that there were at least two major dispersals of modern humans Out of Africa and through Arabia (Out of Africarabia). The first was prior to the Toba eruption of 74,000 years ago and possibly around 130,000 years ago and the second, post-Toba expansion around 60-70,000 years ago. It is most likely that the pre-Toba dispersal was mainly eastwards and following the coastlines and inland only following the major river corridors. Teeth belonging to modern humans, found in the South of China and dated to around 130,000 years ago adds further support to this view.
Christopher J. Bae, Wei Wang, Jianxin Zhao, Shengming Huang, Feng Tian and Guanjun Shen, Modern human teeth from Late Pleistocene Luna Cave (Guangxi, China), DOI: 10.1016/j.quaint.2014.06.051
Abstract: We present two previously unreported hominin permanent teeth [one right upper second molar (M2), one left lower second molar (m2)] from Lunadong (“dong” = “cave”), Guangxi Zhuang Autonomous Region, China. The teeth are important because: 1) they were found in situ; 2) at least one (M2) can be confidently assigned to modern Homo sapiens, while the other (m2) is likely modern H. sapiens; and 3) the teeth can be securely dated between 126.9 ± 1.5 ka and 70.2 ± 1.4 ka, based on multiple MC-ICP-MS uranium-series dates of associated flowstones in clear stratigraphic context. The Lunadong modern H. sapiens teeth contribute to growing evidence (e.g., Callao Cave, Huanglongdong, Zhirendong) that modern and/or transitional humans were likely in eastern Asia between the crucial 120–50 ka time span, a period that some researchers have suggested no hominins were present in the region.
Of course the predecessors of the Neanderthals and the Denisovans also dispersed – perhaps many times – out of Africa from about 500,000 years ago .
I prefer the narrative of a pre-Toba and a much later post-Toba expansion.
Past Horizons: The discovery of two teeth in Lunadong, a cave site located in Guangxi (southern China), lends weight to the possibility that the exodus of modern humans from Africa may have been earlier than 60,000 years ago, as traditionally thought.
Christopher Bae, a palaeoanthropologist at UH Mānoa, and Wei Wang of the Guangxi Museum of Nationalities in Nanning, China, have been leading a team of researchers at the Lunadong cave site.
Found in stratified deposits dating between 70,000 and 126,000 years ago, a period when eastern Asia was traditionally thought to have been only occupied by more archaic human species, at least one of the teeth can be comfortably assigned to modern Homo sapiens.
Dating results of the Lunadong teeth, which include a right upper second molar and a left lower second molar, indicate that they may be as old as 126,000 years.
“The Lunadong modern Homo sapien’s teeth contribute to growing evidence that modern and/or transitional humans were likely in eastern Asia … [during] a period that some researchers have suggested no hominins were present in the region,”the palaeoanthropologists write in the journal Quaternary International.
“The primary point of our paper is that the human evolutionary record, particularly when accounting for increasing finds in eastern Asia, is a lot more complicated than generally believed,” Associate Professor Bae says. “There were probably multiple dispersals of modern humans out of Africa and into Eurasia, with some degree of interbreeding occurring.”
“The findings from the Lunadong study clearly indicate that certain aspects of the Out of Africa model need to be rethought. That is, that there was at least one other earlier Out of Africa migration event that pre-dated 60,000 years ago. This palaeoanthropological find, in addition to other recent studies from western and southern Asia, suggest that modern humans may have dispersed out of Africa in multiple waves rather than as one major single migration event 60,000 years ago as commonly thought,” said Bae.
The Out of Africa theory presently suggests that modern humans migrated from Africa approximately 60,000 years ago following a southern route along the Arabian Peninsula to Southeast Asia. Recent fossil finds in eastern Asia, including the Lunadong teeth, support the theory of a more complicated dispersal model with migrations not only occurring earlier than originally believed, but also involving later dispersal patterns from Northwest Asia to Europe, and finally into Siberia then the Americas.
Other work also supports pre-Toba dispersals.
Earlier work, published in the journal Science, describes findings from an eight-year archaeological excavation at Jebel Faya (2011) in the United Arab Emirates led by Professor Hans-Peter Uerpmann of Eberhard Karls University in Tübingen, Germany.
The researchers analysed the Palaeolithic stone tools found and the site in Sharjah Emirate and concluded they were technologically similar to artefacts produced by early modern humans in east Africa. But they were notably different from tools created to the north, in the Levant and the mountains of Iran.
In light of their excavation, an international team of researchers suggested that humans could have arrived on the Arabian Peninsula as early as 125,000 years ago — directly from Africa rather than via the Nile Valley or the Near East, as suggested in the past. This is 65,000 years earlier than the generally accepted date for the first substantial human migrations beyond Africa, excepting the recent potential find in Israel, which still has to be confirmed, see (New work casts doubt on Out of Africa theory – 28th Dec 2010).
Professor Adrian Parker of Oxford Brookes University, studied sea levels and climate change for the region and concluded that the direct migration route was possible between 140,000 and 130,000 years ago, as the Red Sea was about 100 metres lower than today due to vast quantities of water stored as ice during an earlier Ice Age.
But the establishment view still remains that there was only a post-Toba dispersal of Anatomically Modern Humans. The earlier evidence is usually attributed to being from some primitive homo erectus members.
Human exodus may have reached China 100,000 years ago
OUR direct ancestors may have found their way out of Africa much earlier than we think. As new fossil remains emerge from China and south-east Asia, the traditional story of how we left Africa is being challenged.
The accepted view is that Homo sapiens evolved in Africa 200,000 years ago and stayed there until 60,000 years ago, when they struck out through the Middle East and spread around the world. Any older hominin bones found outside Africa are deemed dead ends. So although the more primitive Homo erectus made it all the way to Indonesia, and probably gave rise to the Neanderthals and the Denisovans, all of these lines eventually died out. Our own species evolved solely in Africa.
The evidence for this comes partly from dating bones to specific periods, but also from genetics. As you move further away from Africa, across Asia and then the Americas, the genetic diversity of indigenous populations drops. This implies that the source population was in Africa and gradually lost diversity as it expanded. The genetics suggest that human genes went through this bottleneck 60,000 years ago.
The “out of Africa at 60,000 years ago“ scenario remains the majority view. But the orthodoxy is slowly being challenged as ancient bones are uncovered in the east. As yet, though, they remain few and far between. ……
…… A closer look at the genetics also suggests there was an earlier migration. Recently, Katerina Harvati of the University of Tubingen in Germany and her colleagues tested the classic “out of Africa at 60,000 years ago” story against the earlier-exodus idea. They plugged the genomes of indigenous populations from south-east Asia into a migration model. They found that the genetic data was best explained by an early exodus that left Africa around 130,000 years ago, taking a coastal route along the Arabian peninsula, India and into Australia, followed by a later wave along the classic route (see map) (PNAS, doi.org/tz6).
An early exit from Africa is still very much a minority view, says Chris Stringer at the Natural History Museum in London. But he says Harvati’s evidence has left him “open to the possibility”.