Southern Route of out of Africa Theory | Middle East And North Africa

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OUT OF AFRICA THEORY AND EARLY MODERN HUMANS

Beginning of the Southern route out of Africa

There are various theories describing how migration patterns played a part in the development of early humans. The traditional, widely-accepted "Single Origin, Out of Africa Theory" of human evolution posits that: 1) earliest hominids evolved in Africa; 2) Australopithecus species evolved into Homo species in Africa; 3) early Homo species migrated to Asia and the Old World from Africa between a million and two million years ago; and 4) Homo sapiens also evolved in Africa and migrated outward from there.

The traditional "Out of Africa" theory holds that there were two migrations of African-originating species. First, Homo erectus began slowly moving into the Middle east, Europe and Asia around 1.8 million years ago. And second, Homo sapiens began migrating into the same areas starting around 100,000 year ago. Scientists that uphold this theory argue that all modern humans have evolved from African Homo sapiens.

Charles Q. Choi wrote in Live Science: “Modern humans expanded out of Africa, spreading rapidly across most of the world's lands to colonize all continents except Antarctica, reaching even the most remote Pacific islands. A number of scientists conjecture this migration was linked with a mutation that transformed our brains, leading to our modern, complex use of language and enabling more sophisticated tools, art and societies. The more popular view suggests hints of such modern behavior existed long before this exodus, and that humanity instead had crossed a threshold in terms of population size in Africa that made such a revolution possible.” [Source: Charles Q. Choi, Live Science, February 22, 2011]

Websites and Resources on Hominins and Human Origins: Smithsonian Human Origins Program humanorigins.si.edu ; Institute of Human Origins iho.asu.edu ; Becoming Human University of Arizona site becominghuman.org ; Hall of Human Origins American Museum of Natural History amnh.org/exhibitions ; The Bradshaw Foundation bradshawfoundation.com ; Britannica Human Evolution britannica.com ; Human Evolution handprint.com ; University of California Museum of Anthropology ucmp.berkeley.edu; John Hawks' Anthropology Weblog johnhawks.net/ ; New Scientist: Human Evolution newscientist.com/article-topic/human-evolution

Migration Routes Out of Africa

single and multiple migration waves into Asia

Modern humans first arose at least 300,000 years ago in Africa. When and how they dispersed from there has been controversial and a topic of fierce debate in the academic community, with geneticists suggesting the exodus started between 40,000 and 70,000 years ago but fossils, artifacts and archaeological evidence saying they left much earlier than that. The currently accepted theory backed up archaeological evidence is that the exodus from Africa followed the “southern route” along Arabia's shores, or possibly through its now-arid interior. Genetic evidence — and some archaeological evidence — supports the “northern route” theory that they traveled through modern-day Egypt, Israel-Palestine to Europe and Asia.

Charles Q. Choi wrote in Live Science: “Scientists had suggested two routes for the exodus from Africa. One, known as the northern route, has humans exiting through what is now Egypt and Sinai. The other, the southern route, brought humans through what is now Ethiopia and Arabia. The available evidence for either migratory path remains inconclusive”. [Source: Charles Q. Choi, Live Science, May 28, 2015]

“The northern route as the preferred way from Africa is supported by the fact that all non-Africans possess DNA from Neanderthals, who were present along the northern route in the eastern Mediterranean at the time. This new finding is also in agreement with the recent discovery of modern human fossils in Israel close to the northern route that date to about 55,000 years ago. Although there is genetic and archaeological evidence that some people did take the southern route out of Africa, perhaps those people got no farther than Arabia, or left no genetic trace in modern Eurasians.”

Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote:“ The consensus view is that if modern humans did exit Africa via a single dispersal, there were two possible routes (not mutually exclusive) at the time: a Northern route, through Egypt and Sinai, and a Southern route, through Ethiopia, the Bab el Mandeb strait, and the Arabian Peninsula. So far, neither archeological nor genetic evidence has been able to resolve this question with confidence.” [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016]

Southern Route Out of Africa

Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “In contrast, mtDNA studies have traditionally favored a Southern route across the Bab el Mandeb strait at the mouth of the Red Sea. From there, modern humans are thought to have spread rapidly into regions of Southeast Asia and Oceania. For example, two studies have concluded that individuals assigned to haplogroup L3 migrated out of the continent via the Horn of Africa. Furthermore, Fernandes et al. analyzed three minor West-Eurasian haplogroups and found a relic distribution of these minor haplogroups suggestive of ancestry within the Arabian cradle, as expected under a Southern route. That being said, many mtDNA studies, including these, are based on the premise that haplogroup L3 represents a remnant Eastern African haplogroup. Groucutt et al have recently theorized that L3 does not provide conclusive evidence for a shared African ancestor, given human demographic history is likely to be less “tree-like” than has been consistently assumed by mtDNA analyses. As an example, they showed that L3 could have arisen inside or outside of Africa if gene flow occurred between the ancestors of Africans and non-Africans following their initial divergence. [Source: Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London, “Human Dispersal Out of Africa: A Lasting Debate,” Evolutionary Bioinformatics, April 21, 2016 ~]

“Short Tandem Repeats (STR) and analysis of LD decay in combination with geographic data have also been used to support a Southern route via a single wave serial bottleneck model. Under this model, it is thought that a group crossed the mouth of the Red Sea and traveled along the Southern coast of the Arabian Peninsula toward India as “beachcombers,” exploiting shellfish and other marine products. Migrations then continued in an iterative wave as populations dispersed and expanded into uninhabited areas. This is consistent with a glacial maximum occurring during this time period, which caused sea levels to fall allowing potential passage across the mouth of the Red Sea. ~

“From an archeological perspective, evidence indicative of maritime exploitation is extremely limited. The discovery of artifacts from the Abdur Reef Limestone in the Red Sea and archeological sites in the Gulf Basin that indicate long-standing human occupation earlier than 100, 000 years ago may offer some evidence; however, whether these represent the activities of the ancestors of modern-day human groups is still an open question. Furthermore, Boivin et al caution that while coastal regions may have been important, a coastal-focused dispersal would still have been problematic and not necessarily conducive to rapid out of Africa dispersal.” ~

Possible migration routes through Arabia and the Middle East to Asia

Tools Found in U.A.E. Imply an Early African Migration Using the Southern Route

Stone tools from the Jebel Faya site in the United Arab Emirates, dated to 120,000 years ago and resembling African artifacts from around the same time, suggest that modern humans migrated out Africa much earlier than thought. Ian Sample wrote in The Guardian: “A spectacular haul of stone tools discovered beneath a collapsed rock shelter in southern Arabia has forced a major rethink of the story of human migration out of Africa. The collection of hand axes and other tools shaped to cut, pierce and scrape bear the hallmarks of early human workmanship, but date from 125,000 years ago, around 55,000 years before our ancestors were thought to have left the continent. The artefacts, uncovered in the United Arab Emirates, point to a much earlier dispersal of ancient humans, who probably cut across from the Horn of Africa to the Arabian peninsula via a shallow channel in the Red Sea that became passable at the end of an ice age. Once established, these early pioneers may have pushed on across the Persian Gulf, perhaps reaching as far as India, Indonesia and eventually Australia. [Source: Ian Sample, The Guardian January 27, 2011 |=|]

“The discovery has sparked debate among archaeologists, some of whom say much stronger evidence is needed to back up the researchers' claims. Some researchers suspect that earlier hominins, not modern humans, made the stone tools, "I'm totally unpersuaded," Paul Mellars, an archaeologist at Cambridge University, told Science. "There's not a scrap of evidence here that these were made by modern humans, nor that they came from Africa." Chris Stringer, a palaeontologist at the Natural History Museum in London, said: "The region of Arabia has been terra incognita in trying to map the dispersal of modern humans from Africa during the last 120,000 years, leading to much theorising in the face of few data. "Despite the confounding lack of diagnostic fossil evidence, this archaeological work provides important clues that early modern humans might have dispersed from Africa across Arabia, as far as the Straits of Hormuz, by 120,000 years ago." |=|

Zach Zorich wrote in Archaeology magazine: Until recently, researchers believed that our species may have made some attempts to travel out of Africa around 120,000 years ago, but had been pushed back by an inhospitable climate and competition with other hominin groups. The prevailing wisdom has been that Homo sapiens didn't make a permanent move into the rest of the world until about 70,000 years ago, presumably when they had achieved some cultural innovations that let them out-compete other hominin species including the now-extinct Homo erectus, Homo heidelbergensis, and Neanderthals. The evidence from Jebel Faya might move that date earlier and add another layer of complexity to the story of modern human migration.[Source: Zach Zorich, Archaeology magazine, May-June 2011]

“While the findings are somewhat circumstantial, they place this migration at roughly the same time that other groups of Homo sapiens are believed to have made their way across the Sinai peninsula at the northern end of the Red Sea to settle sites in modern-day Israel. One additional problematic issue is that the archaeological data doesn't currently match well with the information provided by genetics research. DNA points to the idea that Homo sapiens was present in Southern Asia by 70,000 to 50,000 years ago, but this may just mean that a migration that took place around that time had a much larger impact on the modern gene pool, essentially wiping out any genetic evidence of earlier migrations.

Did Climate Changes Prompt Early African Migrations on the Southern Route

Ian Sample wrote in The Guardian: One strand of the archaeologists' work at Jebel Faya, described in Science, focused on climate change records and historical sea levels in the area. They show that between 200,000 and 130,000 years ago, a global ice age caused sea levels to fall by up to 100 metres, while the Saharan and Arabian deserts expanded into vast, inhospitable wastelands. But as the climate warmed at the end of the ice age, fresh rains fell on Arabia, opening up the region to human occupation. "The previously arid interior of Arabia would have been transformed into a landscape covered largely in savannah grasses, with extensive lakes and river systems," said Adrian Parker, a researcher at Oxford Brookes University and co-author of the paper. “The revival of Arabia coincided with record lows in sea level, which left only a shallow stretch of water about three miles wide at the Bab al Mandab Straits separating east Africa and the Arabian peninsula. Uerpmann said early humans may have walked or waded across, but added: "They could have used rafts or boats, which they certainly could make at that time." The new arrivals would have found good hunting grounds at the end of their journey, with plentiful wild asses, gazelles and mountain ibex, Uerpmann said. [Source: Ian Sample, The Guardian January 27, 2011 |=|]

Project archaeologist Anthony Marks of Southern Methodist University thinks the shifting climate opened new territory for human exploration. He told Discover: We now know that 130,000 years ago, the Indian Ocean monsoons pushed farther north, and Arabia became grassland.” [Source: Mary Beth Griggs, Discover, December 22, 2011]

Zach Zorich wrote in Archaeology magazine: “When glaciers in Europe and Asia were at their largest, from about 200,000 to 135,000 years ago, the Arabian Peninsula was drier. The expanding deserts would have served as barriers to people attempting to migrate from Africa at that time. Earlier hominins, such as Homo erectus, had the advantage of leaving Africa millions of years earlier, probably while the Arabian Peninsula was relatively wet, making it easier to travel and find food. Homo sapiens may not have been able to expand into the rest of the world because they hadn't developed techniques to carry enough provisions to cross the deserts. They may only have been capable of leaving Africa when the wetter conditions created by retreating glaciers made it possible for them to do so. Uerpmann says, "Now we see that it was the environment that was the key to this [leaving Africa]." According to the climate data assembled by the team's paleoclimatologist, Adrian Parker of Oxford Brookes University, between 135,000 and 120,000 years ago, the water level in the Red Sea would have been low enough to make the crossing to the Arabian Peninsula possible and it would have had a mild enough climate to make it inviting to people looking for a new home. [Source: Zach Zorich, Archaeology magazine, May-June 2011]

“The climate, however, is believed to have become, once again, much drier by some 90,000 years ago. The earliest people at Jebel Faya may then have gone back to Africa when the climate became inhospitable and it may be that this early attempt by Homo sapiens to expand their range beyond Africa failed — even if temporarily. The sites of Skhul and Qafzeh in modern-day Israel contain evidence that Homo sapiens lived at those sites around 120,000 to 81,000 years ago, but then evidence of them also disappears. And while stone tools recovered from the site of Jwalapuram in India indicate that Homo sapiens may have made it there by about 78,000 years ago, there are no human bones to confirm conclusively that the species lived at the site. It is still possible, then, that the migration that led Homo sapiens to finally spread across the globe took place later.

finger bones from Saudi Arabia

90,000-Year-Old Human Middle Finger Bone Found in Saudi Arabia

In 2016, archaeologists in Saudi Arabia announced the discovery of a human fossil bone — the middle section of the middle finger — which was dated to be 90,000 years old, the oldest evidence modern humans on the Arabian Peninsula, an official from the Saudi Commission for Tourism and National Heritage told Al-Arabiya. The Saudis claimed it was the oldest human bone ever found. [Source: Jack Moore, Newsweek, August 19, 2016 -]

Jack Moore wrote in Newsweek: “Researchers from a joint Saudi-U.K. project, which included the Saudi archaeologists and University of Oxford experts, made the find at the Taas al-Ghadha site near to the northwestern Saudi city of Tayma. The project is an extension of the Green Arabia Project, which is studying sites near ancient lakes in the Nafud desert. Archaeologists began digging in the area in 2012. -

“Its historic discovery suggests that human life dated back as far as 325,000 years, head of the Saudi Commission for Tourism and National Heritage Ali Ghabban said. He did not elaborate on why the find of a 90,000-year-old bone led to this assumption. The Board of the Saudi Commission for Tourism and National Heritage, said that the discovery is “considered an important achievement for the Saudi researchers who participated in these missions and one of the most important outcomes of Prince Sultan’s support and care for the archaeology sector in the Kingdom.” -

While the Saudis are claiming to have found the oldest ever human bone, the oldest bone ever discovered belonging to the lineage that developed into human beings, the Homo genus, is a jaw bone found in Ethiopia in 2015. It is dated to 2.8 million years ago. The oldest modern human discovered at that time was a 195,000-year-old fossil from Ethiopia. Since then 300,000-year-old modern human fossils have been found in Morocco.

Oman Artifacts Suggest Early Humans Traveled Inland in Arabia Rather Along the Coast

It has been presumed that when modern humans emerged from Africa and traveled through the Arabian Peninsula, they did so by hugging the coast, which had a less harsh climate and easier-to-obtain food sources. However, 100,000-year-old stone tools found in the Dhofar Mountains suggest that some people traveled over the now arid — though once wet — interior. The find adds another layer of complexity and understanding to the path that modern humans took on their way around the world. [Source: Archaeology magazine, March-April 2012]

Charles Q. Choi wrote in Live Science: “More than 100 newly discovered sites in the Sultanate of Oman apparently confirm that modern humans left Africa through Arabia long before genetic evidence suggests. Oddly, these sites are located far inland, away from the coasts. "After a decade of searching in southern Arabia for some clue that might help us understand early human expansion, at long last we've found the smoking gun of their exit from Africa," said lead researcher Jeffrey Rose, a paleolithic archaeologist at the University of Birmingham in England. "What makes this so exciting is that the answer is a scenario almost never considered." [Source: Charles Q. Choi, Live Science, November 30, 2011 *]

“The international team of archaeologists and geologists made their discovery in the Dhofar Mountains of southern Oman, nestled in the southeastern corner of the Arabian Peninsula. "The coastal expansion hypothesis looks reasonable on paper, but there is simply no archaeological evidence to back it up," said researcher Anthony Marks of Southern Methodist University, referring to the fact that an exodus by the coast, where one has access to resources such as seafood, might make more sense than tramping across the desert.. *\

“The 100-to-200 artifacts they found there were of a style dubbed Nubian Middle Stone Age, well-known throughout the Nile Valley, where they date back about 74,000-to-128,000 years. Scientists think ancient craftsmen would have shaped the artifacts by striking flakes off flint, leading to distinctive triangular pieces. This is the first time such artifacts have been found outside of Africa. *\

“Subsequent field work turned up dozens of sites with similar artifacts. Using a technique known as optically stimulated luminescence dating, which measures the minute amount of light long-buried objects can emit, to see how long they have been interred, the researchers estimate the artifacts are about 106,000 years old, exactly what one might expect from Nubian Middle Stone Age artifacts and far earlier than conventional dates for the exodus from Africa. *\

“Finding so much evidence of life in what is now a relatively barren desert supports the importance of field work, according to the researchers. "Here we have an example of the disconnect between theoretical models versus real evidence on the ground," Marks said. However, when these artifacts were made, instead of being desolate, Arabia was very wet, with copious rain falling across the peninsula, transforming its barren deserts to fertile, sprawling grasslands with lots of animals to hunt, the researchers explained. "For a while, South Arabia became a verdant paradise rich in resources — large game, plentiful fresh water, and high-quality flint with which to make stone tools," Rose said. *\

“Instead of hugging the coast, early modern humans might therefore have spread from Africa into Arabia along river networks that would've acted like today's highways, researchers suggested. There would have been plenty of large game present, such as gazelles, antelopes and ibexes, which would have been appealing to early modern humans used to hunting on the savannas of Africa. "The genetic signature that we've seen so far of an exodus 70,000 years ago might not be out of Africa, but out of Arabia," Rose told LiveScience. *\

“So far the researchers have not discovered the remains of humans or any other animals at the site. Could these tools have been made by now-extinct human lineages such as Neanderthals that left Africa before modern humans did? Not likely, Rose said, as all the Nubian Middle Stone Age tools seen in Africa are associated with our ancestors. It remains a mystery as to how early modern humans from Africa crossed the Red Sea, since they did not appear to enter the Arabian Peninsula from the north, through the Sinai Peninsula, Rose explained. "Back then, there was no land bridge in the south of Arabia, but the sea level might not have been that low," he said. Archaeologists will have to continue combing the deserts of southern Arabia for more of what the researchers called a "trail of stone breadcrumbs." The scientists detailed their findings online November 30, 2011 in the journal PLoS ONE.” *\

Ancient Arabian Stone Tools Hint of Multiple Migrations Out of Africa

Arabian stone tools from different periods of time tens of thousands of years ago hint of multiple migrations out of Africa. Charles Q. Choi wrote in Live Science: To help shed light on the role the Arabian Peninsula might have played in the history of modern humans, scientists compared stone artifacts recently excavated from three sites in the Jubbah lake basin in northern Saudi Arabia with items from northeast Africa excavated in the 1960s. Both sets of artifacts were 70,000 to 125,000 years old. Back then, the areas that are now the Arabian and Sahara deserts were far more hospitable places to live than they are now, which could have made it easier for modern humans and related lineages to migrate out of Africa. "Understanding how we originated and colonized the world remains one of the most fascinating and enduring questions, because it is our story as humans," said lead study author Eleanor Scerri, an archaeologist at the University of Bordeaux in France. [Source: Charles Q. Choi, Live Science, August 27, 2014]

"Far from being a desert, the Arabian Peninsula between 130,000 and 75,000 years ago was a patchwork of grasslands and savanna environments, featuring extensive river networks running through the interior," Scerri said. The northeast African stone tools the researchers analyzed were similar to ones previously found near modern-human skeletons. The scientists found that stone artifacts at two of the three Arabian sites were "extremely similar" to the northeast African stone tools, Scerri told Live Science. At the very least, Scerri said, this finding suggests that there was some level of interaction between the groups in Africa and those in the Arabian Peninsula, and might hint that these Arabian tools were made by modern humans.

Surprisingly, Scerri said, tools from the third Arabian site the researchers analyzed were "completely different." "This shows that there was a number of different tool-making traditions in northern Arabia during this time, often in very close proximity to each other," she said. One possible explanation for these differences is that the artifacts were made by different human lineages. Future research needs to uncover skeletal remains with ancient tools unearthed from the Arabian Peninsula to help solve this mystery, Scerri noted. Unless skeletal remains are found near such artifacts, it will remain uncertain whether modern humans or a different human lineage might have made them.

"It seems likely that there were multiple dispersals into the Arabian Peninsula from Africa, some possibly very early in the history of Homo sapiens," Scerri said. "It also seems likely that there may have been multiple dispersals into this region from other parts of Eurasia. These features are what make the Arabian Peninsula so interesting." Ancient migrants out of Africa and from Eurasia might have encountered a number of different populations in the Arabian Peninsula, Scerri said. Some of these groups may have adapted to their environment more than others had, which raises the intriguing question: "Did the exchange of genes and knowledge between such groups contribute to our ultimate success as a species?" Scerri said. The scientists detailed their findings online August 8, 2014 in the Journal of Human Evolution.

Image Sources: Wikimedia Commons except Africa sites, Science magazine, and Middle East migration routes, researchgate.com

Text Sources: National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Live Science, Discover magazine, Discovery News, Natural History magazine, Archaeology magazine, The New Yorker, Time, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.

Last updated April 2024