Differentiation after dispersal out of Africa in the Early Upper Paleolithic (45,000–20,000 years)

Our direct human ancestors, likely left Africa multiple times, perhaps as early as 200,000 years, but archaeologists and geneticists largely agree that the most significant dispersal of Homo sapiens, our own species took place around 70,000 to 50,000 years ago, and these people ltimately spread to to every corner of the globe.

DNA studies of people living today indicate that modern humans migrated from Eastern Africa to the Middle East, then Southern and Southeast Asia, then New Guinea and Australia, followed by Europe and Central Asia. Perhaps they didn't enter Europe because that region was dominated by Neanderthals. According to research by geneticist at the University of Cambridge in the mid 2000s all modern humans descend from a small number of Africans that left Africa between 55,000 and 60,000 years ago. Another DNA less reliable study determined that an intrepid group of 500 hominids marched out of Africa about 140,000 years ago and they are the ancestors to all modern people today. [Source: Guy Gugliotta, Smithsonian magazine, July 2008]

These studies are based on genetic variations found in different population groups. People in sub-Saharan Africa have more genetic variation than non-Africans. The number of people and the date for the 140,000 year figure was arrived by studying genetic variations in 34 populations around the world, coming up with a rate of genetic change and extrapolated back in time. The fact that people in sub-Saharan Africa have more genetic variation than non-Africa indicated humans that have lived in Africa have lived there longer than other people have lived in their homelands.

The earliest known mutation to spread outside Africa is M168, which developed about 50,000 years ago. It is found in all non-Africans. M9 is a marker common in Eurasians. It appeared in the Middle East or Central Asia about 40,000 years ago. M3 is a marker that developed among Asian people around 10,000 years ago and reached the Americas.

Based on genetic evidence gathered by National Geographic magazine and scientists from around the globe it has been determined that modern humans originated in southern Africa around 200,000 years ago and made to West Africa about 70,000 years ago and the Middle East about 50,000 years ago, advancing rapidly through southern and southeast Asia and reaching Australia also around 50,000 years ago but not reach East Asia and Siberia until 30,000 years ago and southern Europe until 20,000 years. From Siberia modern humans reached North America about 15,000 years ago and migrated southward reaching South America between 13,000 and 15,000 years ago. The group living today with the closest links to our 200,000-year-old ancestors in southern Africa are the Khoisan hunter-gatherers of southern Africa. [Source: National Geographic, November, 2009]

Some scientists feel the migration out of Africa was also accompanied by revolutions in behavior and technology such as more developed social networks and advanced tools and sophisticated language that gave them ability to prosper in new lands and in some cases drive out hominids that already lived there.

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

Out of Africa Theory and Early Modern Humans

Migration map of Haplogroup D (CTS3946) of the human Y chromosome, showing an early divergence between clades D0 (A5580.2) and D1 (M174)

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]

Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Unraveling the first migrations of anatomically modern humans out of Africa has invoked great interest among researchers from a wide range of disciplines. Available fossil, archeological, and climatic data offer many hypotheses, and as such genetics, with the advent of genome-wide genotyping and sequencing techniques and an increase in the availability of ancient samples, offers another important tool for testing theories relating to our own history. In this review, we report the ongoing debates regarding how and when our ancestors left Africa, how many waves of dispersal there were and what geographical routes were taken.” [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]

Migration Routes Out of Africa

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.”

Possible migration routes through the Middle East

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]

Northern Route Out of Africa

Saioa López, Lucy van Dorp and Garrett Hellenthal of University College London wrote: “Some of the earliest remains of Anatomically modern humans anywhere outside of Africa, the Skhul and Qafzeh hominins, were found in the Levant (present-day Israel) and dated to 120 and 100,000–90,000 years ago, respectively. It has been suggested that these fossils represent an early exit of modern humans approximately 120,000 years ago, traveling across the Sinai Peninsula to the Levant. The next human remains found in the region include the Manot1 cranium, which was dated to around 55,000 years ago, demonstrating a considerable gap in the fossil record of Anatomically modern human occupation in the Levant. This, in conjunction with climatic records, indicating a global glacial period 90,000 years ago, has led some authors to suggest that if the first humans did exit early via the Levant they did not survive, and that the Skhul and Qafzeh hominins are the remnants of this failed exodus. Other authors emphasize the possibility that this group could have already left the Levant before the glacial period 90,000 years ago. That said, the recent presentation of archeological material, primarily stone tools and assemblages dated to 100,000–80,000 years ago, from an empty corner of the Arabian Peninsula suggests early settlements may have been widely distributed and that even if Skhul and Qafzeh do represent a failed exodus, it was broader and more complex than previously thought. [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 ~]

“In addition to the evidence from the archeological and climatic record, genetic studies have also suggested some support for a Northern route. A study of Y chromosome haplogroup distributions together with 10 microsatellite loci and 45 binary markers in different African and Near Eastern populations found that the Levant was the most supported route for the primary migratory movements between Africa and Eurasia. In a more recent paper, Pagani et al sequenced the genomes of 100 Egyptians and 125 individuals from five Ethiopian ethnic groups (Amhara, Oromo, Ethiopian Somali, Wolayta, and Gumuz).64 After attempting to mask West Eurasian genetic components inherited via recent non-African admixture within the last 4,000 years ago, they showed that modern non-African haplotypes were more similar to Egyptian haplotypes than to Ethiopian haplotypes, thus suggesting that Egypt was the more likely route in the exodus out of Africa migration, assuming the efficacy of their masking procedure. However, as noted earlier, one limitation of such studies that analyze modern DNA is that extant populations may not be good representatives of past populations due to factors such as population replacement, migrations, admixture, and drift.” ~

Southern Route Out of Africa

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.” ~

First Humans to Leave Africa Settled in Iraq, Iran and Arabia Before Moving On

Maybe the first wave of modern humans began leaving Africa about 180,000 to 120,000 years ago but large migrations out of the continent didn’t appear to occur until around 60,000 to 70,000 — but where did these peoplego. Reuters reported: After years of debate, a new study offers an answer. These bands of hunter-gatherers appear to have lingered for thousands of years as a homogeneous population in a geographic hub that spanned Iran, southeast Iraq and northeast Saudi Arabia before going on to settle all of Asia and Europe starting roughly 45,000 years ago, scientists said on Monday. [Source: Reuters, March 2024]

“Their findings were based on genomic datasets drawn from ancient DNA and modern gene pools, combined with paleoecological evidence that showed that this region would have represented an ideal habitat. The researchers called this region, part of what is called the Persian Plateau, a "hub" for these people - who numbered perhaps only in the thousands - before they continued onward millennia later to more distant locales. "Our results provide the first full picture of the whereabouts of the ancestors of all present-day non-Africans in the early phases on the colonization of Eurasia," said molecular anthropologist Luca Pagani of the University of Padova in Italy, senior author of the study published in the journal Nature Communications.

Two possible models of L3's dispersal according to the Africa origin hypothesis: (a) Haplogroup N differentiates from L3 in the African continent, with a subsequent spread out of Africa.

Anthropologist and study co-author Michael Petraglia, director of the Australian Research Centre for Human Evolution at Griffith University, said the study "is a story about us and our history - our goal was to unravel some of the mystery about our evolution and our worldwide dispersal. The combination of genetic and paleoecological models allowed us to predict the location where early human populations first resided as soon as they exited Africa."

These people lived in small, mobile bands of hunter-gatherers, the researchers said. The hub location offered a variety of ecological settings, from forests to grasslands and savannahs, fluctuating over time between arid and wet intervals. There would have been ample resources available, with evidence showing the hunting of wild gazelle, sheep and goat, Petraglia said. "Their diet would have been composed of edible plants and small- to large-sized game. Hunter-gatherer groups seemed to have practiced a seasonal lifestyle, living in the lowlands in the cooler months and in the mountainous regions in the warmer months," Petraglia said.

The people inhabiting the hub at the time apparently had dark skin and dark hair, perhaps resembling the Gumuz or Anuak people now living in parts of East Africa, Pagani said. "Cave art simultaneously appeared as soon as people left the hub. So these cultural achievements might have been brewed while in the hub," Pagani said. Their eventual dispersal in different directions beyond the hub set the basis for the genetic divergence between present-day East Asians and Europeans, the researchers said.

The study tapped into modern and ancient genomic data for European and Asian people. "We found particularly useful the oldest genomes, dating from 45,000 to 35,000 years ago," said molecular anthropologist and study lead author Leonardo Vallini of the University of Padova and the University of Mainz in Germany. The researchers devised a way to disentangle the extensive genetic mixing of populations that has occurred since the dispersal out of the hub in order to pinpoint this region.

There were earlier small-scale excursions of Homo sapiens out of Africa before the pivotal migration 60,000 to 70,000 years ago, but these appear to have been dead-ends. Homo sapiens was not the first human species to live outside of Africa - including the area encompassing the hub. Ancient interbreeding by our species has left a small Neanderthal contribution to the DNA of modern non-Africans. "Neanderthals are attested in the area before the arrival of Homo sapiens, so the hub may well have been where that interaction took place," Vallini said.

Modern Humans in Australia 65,000 Years Ago Challenges Migration Models

Fossils of similar age have been found in Asia but the oldest modern man fossils found in Europe are about 45,000 years old. This means that modern man made its way its way from across Asia and took boats to Australia around 20,000 years before they traversed a much shorter distance to Europe. One explanation for the delay in occupying Europe is the presence of Neanderthals there.

Recently discovered archaeological evidence suggesting the first Australians arrived at least 65,000 years ago, Gemma Tarlach wrote, in Discover magazine, is “at odds with the conventional date for our species leaving Africa, and adds fuel to the growing bonfire of what was the evolutionary timeline for Homo sapiens. For decades, the hoary old story of human evolution and migration went something like this: An archaic version of Homo sapiens evolved in Africa around 200,000 years ago, and eventually amassed enough random advantageous mutations to get upgraded to version 2.0 (thanks, natural selection!), aka modern Homo sapiens, by about 100,000 years ago. Then, the timeline gets a bit iffy. Many paleoanthropologists had long argued that our species didn’t leave Africa until 60,000 years ago — some put the date even later, around 40,000 years ago. That’s what the archaeological evidence told them, and that’s what they stuck hard and fast to. [Source: Gemma Tarlach, Discover, July 19, 2017 /]

(b) Haplogroups M and N diverged from L3 outside Africa or during the expansion of L3-carrying AMH out of the continent; later migrations during Early Upper Paleolithic and the Neolithic diffusion led some lineages back to North Africa.

“Since the 1990s, however, a growing number of studies — increasingly driven by genetic evidence — have painted a very different picture of human evolution and migration. Most recently, in 2016 a landmark genomic study of 400 Papua New Guineans suggested that modern Homo sapiens may have arrived in the region 120,000 years ago. And earlier this month, the sequencing of ancient mitochondrial (maternally-inherited) DNA extracted from a Neanderthal femur hinted that African Homo sapiens were interbreeding with European Neanderthals more than 200,000 years ago. /\

“Then there was the announcement earlier this year that Homo sapiens — albeit not quite version 2.0 — were in Morocco 300,000 years ago — the best evidence yet that our species is considerably older than we thought. Enter The First Australians Question. As one of the corners of the world furthest-flung from Africa, it makes sense that our species would arrive there fairly late in its relentless march across the planet. Many old-schoolers believed humans first set foot in Australia anywhere from 20,000-40,000 years ago. /\

Did the Toba Supervolcano Eruption 74,000 Years Ago Facilitate the Out of Africa Migration?

Katie Hunt of CNN wrote: About 74,000 years ago, Sumatra’s Mount Toba experienced a super-eruption, one of the largest in Earth’s history, potentially kicking off a massive disruption in the world’s climate.Some scientists have suspected a volcanic winter resulting from the eruption was a big enough shift to wipe out most early humans due to genetic evidence suggesting a steep drop in the human population. But now a study on an archaeological site in northwest Ethiopia once occupied by early modern humans has added to a growing body of evidence that suggests the event might not have been so apocalyptic. [Source: Katie Hunt, CNN March 22, 2024]

Instead, the new research found humans in that location, known as Shinfa-Metema 1, adapted to the arid conditions brought on by the volcanic eruption in a way that may have facilitated humanity’s pivotal migration out of Africa to the rest of the world.Microscopic fragments of volcanic glass found alongside stone tools and animal remains in the same layer of sediment at the Shinfa-Metema 1 site, near Ethiopia’s Shinfa River, show humans were occupying the site before and after the volcano erupted more than 4,000 miles away.“These fragments are less than the diameter of a human hair. Even as tiny as (that) they are still big enough to analyze the chemistry and the trace elements,” said John Kappelman, a professor of anthropology and geological science at the University of Texas at Austin and lead author of the study, which published Wednesday in the journal Nature.

By piecing together clues from the fossils and artifacts found at the site, along with geological and molecular analysis, the team began to understand how the humans living there forged ahead despite the likely climate shift that the volcanic cataclysm triggered. To understand the climate around the time of the eruption, Kappelman and his colleagues analyzed oxygen and carbon isotopes, variations of the same element, from ostrich eggshells and fossilized mammal teeth. That work shed light on water intake and revealed the animals ate plants that were more likely to grow in drier conditions.“The isotopes are incorporated in the hard tissues. So for the mammals, we look at their teeth, the enamel of their teeth, but we also find it in the eggshell of the ostrich,” he said.

An analysis of the site’s flora and fauna also found an abundance of fish remains in the aftermath of the eruption. The finding is perhaps not surprising given how near the site was to the river, but fish are rare in other Stone Age sites from the same period, the study noted. “People start to increase the percentage of fish in the diet when Toba comes in. They’re capturing and processing almost four times as much fish (as before the eruption),” he said.“We think the reason for that is because if Toba is in fact, creating more aridity, that means it’s going to be a shorter wet season, which means longer dry season.” The team theorized that the drier climate, counterintuitively, explains the increased reliance on fish: As the river shrank, fish were trapped in water holes or shallower streams that hunters could more easily target.

The fish-rich water holes may have potentially created what the team described as a “blue corridor,” along which early humans moved north out of Africa once they were depleted of fish. This theory contradicts most other models that suggest that humanity’s main migration out of Africa took place along “green corridors” during humid periods. “This study … demonstrates the great plasticity of Homo sapiens populations and their ability to adapt easily to any type of environment, whether hyper-humid or hyper-arid, including during catastrophic events such as the hyper-explosion of the Toba volcano,” said Ludovic Slimak, a researcher at the French National Centre for Scientific Research and the University of Toulouse, in an email. Slimak was not involved in the research.

Humans in the Arctic 45,000 Years Ago?

Ann Gibbons wrote in Science: “In August of 2012, an 11-year-old boy made a gruesome discovery in a frozen bluff overlooking the Arctic Ocean. While exploring the foggy coast of Yenisei Bay, about 2000 kilometers south of the North Pole, he came upon the leg bones of a woolly mammoth eroding out of frozen sediments. Scientists excavating the well-preserved creature determined that it had been killed by humans: Its eye sockets, ribs, and jaw had been battered, apparently by spears, and one spear-point had left a dent in its cheekbone—perhaps a missed blow aimed at the base of its trunk. [Source: Ann Gibbons, Science, January 14, 2016 ^]

“When they dated the remains, the researchers got another surprise: The mammoth died 45,000 years ago. That means that humans lived in the Arctic more than 10,000 years earlier than scientists believed, according to a new study. The find suggests that even at this early stage, humans were traversing the most frigid parts of the globe and had the adaptive ability to migrate almost everywhere. ^

“Most researchers had long thought that big-game hunters, who left a trail of stone tools around the Arctic 12,500 years ago, were the first to reach the Arctic Circle. These cold-adapted hunters apparently traversed Siberia and the Bering Straits at least 15,000 years ago (and new dates suggest humans may have been in the Americas as early as 18,500 years ago). But in 2004, researchers pushed that date further back in time when they discovered beads and stone and bone tools dated to as much as 35,000 years old at several sites in the Ural Mountains of far northeastern Europe and in northern Siberia; they also found the butchered carcasses of woolly mammoths, woolly rhinoceros, reindeer, and other animals. The Russian boy’s discovery—of the best-preserved mammoth found in a century—pushes back those dates by another 10,000 years. A team led by archaeologist Alexei Tikhonov excavated the mammoth and dubbed it “Zhenya,” for the child, Evgeniy Solinder, whose nickname was Zhenya. ^

“The big surprise, though, is the age. Radiocarbon dates on the collagen from the mammoth’s tibia bone, as well as from hair and muscle tissue, produce a direct date of 45,000 years, the team reports online today in Science. This fits with dating of the layer of sediments above the carcass, which suggest it was older than 40,000 years. If correct, this means the mammoth was alive during the heyday of woolly mammoths 42,000 to 44,000 years ago when they roamed the vast open grasslands of the northern steppe of the Siberian Arctic, Pitulko says. Researchers also have dated a thighbone of a modern human to 45,000 years at Ust-Ishim in Siberia, although that was found south of the Arctic at a latitude of 57° north, a bit north (and east) of Moscow. “The dating is compelling. It’s likely older than 40,000,” says Douglas Kennett, an environmental archaeologist who is co-director of the Pennsylvania State University, University Park’s accelerator mass spectrometry facility. However, he would like the Russian team to report the method used to rule out contamination of the bone collagen for dating—and confirmation of the dates on the bone by another lab, because the date is so critical for the significance of this discovery. ^

“Mammoths and other large animals, such as woolly rhinoceros and reindeer, may have been the magnet that drew humans to the Far North. “Mammoth hunting was an important part of survival strategy, not only in terms of food, but in terms of important raw materials—tusks, ivory that they desperately needed to manufacture hunting equipment,” Pitulko says. The presence of humans in the Arctic this early also suggests they had the adaptive ability to make tools, warm clothes, and temporary shelters that allowed them to live in the frigid north earlier than thought. They had to adapt to the cold to traverse Siberia and Beringia on their way to the Bering Strait’s land bridge, which they crossed to enter the Americas. “Surviving at those latitudes requires highly specialized technology and extreme cooperation,” Marean agrees. That implies that these were modern humans, rather than Neandertals or other early members of the human family. “If these hunters could survive in the Arctic Circle 45,000 years ago, they could have lived virtually anywhere on Earth,” says Ted Goebel, an archaeologist at Texas A&M University, College Station.” ^

The find also indicates that early Siberians were 4,660 kilometers (2,895 miles) from what was then a land bridge between modern Russia and Alaska. According to the Siberian Times: “A long distance, for sure, but far from insurmountable, opening the possibility that Stone Age Siberians colonised the Americas at this early point.” [Source: Anna Liesowska siberiantimes.com May 30, 2016]

should start with humans in Morocco 300,000 years ago but gives a good idea of how the migrations worked

Where Modern Humans Innate Explorers

“No other mammal moves around like we do,” says Pääbo told National Geographic.“We jump borders. We push into new territory even when we have resources where we are. Other animals don’t do this. Other humans either. Neanderthals were around hundreds of thousands of years, but they never spread around the world. In just 50,000 years we covered everything. There’s a kind of madness to it. Sailing out into the ocean, you have no idea what’s on the other side. And now we go to Mars. We never stop. Why?” [Source: David Dobbs, National Geographic, January 2013]

Elizabeth Kolbert wrote in The New Yorker: “From the archeological record, it’s inferred that Neanderthals evolved in Europe or western Asia and spread out from there, stopping when they reached water or some other significant obstacle. (During the ice ages, sea levels were a lot lower than they are now, so there was no English Channel to cross.) This is one of the most basic ways modern humans differ from Neanderthals and, in Pääbo’s view, also one of the most intriguing. By about forty-five thousand years ago, modern humans had already reached Australia, a journey that, even mid-ice age, meant crossing open water. Archaic humans like Homo erectus “spread like many other mammals in the Old World,” Pääbo told me. “They never came to Madagascar, never to Australia. Neither did Neanderthals. [Source: Elizabeth Kolbert, The New Yorker, August 15, 2011 ^^]

“It’s only fully modern humans who start this thing of venturing out on the ocean where you don’t see land. Part of that is technology, of course; you have to have ships to do it. But there is also, I like to think or say, some madness there. You know? How many people must have sailed out and vanished on the Pacific before you found Easter Island? I mean, it’s ridiculous. And why do you do that? Is it for the glory? For immortality? For curiosity? And now we go to Mars. We never stop.” If the defining characteristic of modern humans is this sort of Faustian restlessness, then, by Pääbo’s account, there must be some sort of Faustian gene. Several times, he told me that he thought it should be possible to identify the basis for this “madness” by comparing Neanderthal and human DNA. ^^

““If we one day will know that some freak mutation made the human insanity and exploration thing possible, it will be amazing to think that it was this little inversion on this chromosome that made all this happen and changed the whole ecosystem of the planet and made us dominate everything,” he said at one point. At another, he said, “We are crazy in some way. What drives it? That I would really like to understand. That would be really, really cool to know.”“ ^^

Explorer Genes?

David Dobbs wrote in National Geographic:: “If an urge to explore rises in us innately, perhaps its foundation lies within our genome. In fact there is a mutation that pops up frequently in such discussions: a variant of a gene called DRD4, which helps control dopamine, a chemical brain messenger important in learning and reward. Researchers have repeatedly tied the variant, known as DRD4-7R and carried by roughly 20 percent of all humans, to curiosity and restlessness. Dozens of human studies have found that 7R makes people more likely to take risks; explore new places, ideas, foods, relationships, drugs, or sexual opportunities; and generally embrace movement, change, and adventure. Studies in animals simulating 7R’s actions suggest it increases their taste for both movement and novelty. (Not incidentally, it is also closely associated with ADHD.) [Source: David Dobbs, National Geographic, January 2013 ||]

“Most provocatively, several studies tie 7R to human migration. The first large genetic study to do so, led by Chuansheng Chen of the University of California, Irvine in 1999, found 7R more common in present-day migratory cultures than in settled ones. A larger, more statistically rigorous 2011 study supported this, finding that 7R, along with another variant named 2R, tends to be found more frequently than you would expect by chance in populations whose ancestors migrated longer distances after they moved out of Africa. Neither study necessarily means that the 7R form of the gene actually made those ancestors especially restless; you’d have to have been around back then to test that premise with certainty. But both studies support the idea that a nomadic lifestyle selects for the 7R variant. ||

“Another recent study backs this up. Among Ariaal tribesmen in Africa, those who carry 7R tend to be stronger and better fed than their non-7R peers if they live in nomadic tribes, possibly reflecting better fitness for a nomadic life and perhaps higher status as well. However, 7R carriers tend to be less well nourished if they live as settled villagers. The variant’s value, then, like that of many genes and traits, may depend on the surroundings. A restless person may thrive in a changeable environment but wither in a stable one; likewise with any genes that help produce the restlessness. ||

“So is 7R the explorer’s gene or adventure gene, as some call it? Yale University evolutionary and population geneticist Kenneth Kidd thinks that overstates its role. Kidd speaks with special authority here, as he was part of the team that discovered the 7R variant 20 years ago. Like other skeptics, he thinks that many of the studies linking 7R to exploratory traits suffer from mushy methods or math. He notes too that the pile of studies supporting 7R’s link with these traits is countered by another stack contradicting it. “You just can’t reduce something as complex as human exploration to a single gene,” he says, laughing. “Genetics doesn’t work that way.” |

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

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