It’s Official: Timeline For Human Migration Gets A Rewrite

By Gemma Tarlach | December 7, 2017 1:00 pm
The traditional story of human migration out of Africa to points north and east has been on shaky ground for years. Researchers in a new Science paper are finally calling for a revision. (Archaic Homo sapiens photographed at the Smithsonian Museum of Natural History, Credit Ryan Somma/Wikimedia Commons)

The traditional story of human migration out of Africa has been on shaky ground for years. Researchers in a new Science paper are finally calling for a revision. (Archaic Homo sapiens photographed at the Smithsonian National Museum of Natural History, credit Ryan Somma/Wikimedia Commons)

The wealth of new paleoanthropological, archaeological and genetic evidence has passed the tipping point: In a review published today in the prestigious journal Science, researchers acknowledge that the conventional timeline of human migration out of Africa “can no longer be considered valid.”

The idea of an African homeland for our species is less than a century old, rooted in the discovery of early hominin fossils in South Africa in the ’20s and championed by individuals such as Raymond Dart, who were initially dismissed and even ridiculed. Then more fossils were unearthed, particularly in eastern Africa, and the general consensus shifted. In the span of a couple decades or so, the idea that Homo sapiens evolved in Africa went from fringe theory to mainstream thinking*.

(*That said, there is a minority in the field, particularly researchers in East Asia, who believe no single location can claim to be the cradle of humanity. Rather, they argue that archaic populations of Homo erectus evolved regionally. More on this school of thought in a bit.)

Once the idea of an African homeland took hold, the question became how and when did modern humans road trip their way off the continent and across the globe.

Based on what fossils and artifacts they had, researchers constructed a timeline that modern humans evolved in Africa about 100,000 years ago and left the continent 50,000-60,000 years ago, going on their merry way in all directions across Eurasia and wiping out the Neanderthals (oops, sorry, Neanderthals).

Here’s the problem. Almost as soon as this timeline became a thing, new research turned up evidence that contradicted it.

Fossils with modern traits have been found from Morocco to China tens of thousands of years — even hundreds of thousands, in the case of the Morocco find — before the old timeline declared it possible. Analysis of both modern and ancient DNA has revealed a whole new hominin, the Denisovans, as well as multiple episodes of interbreeding between H. sapiens, Neanderthals and Denisovans, sometimes much earlier — and much further from Africa — than that pesky timeline allowed.

It’s About Time

The great thing about science is supposed to be that you come up with a hypothesis and then you and other researchers try to shoot it down and, if the hypothesis doesn’t hold up, you come up with a new one based on what you learned from destroying the old one. And the scientific method generally works, as long as everyone keeps their egos in check.

Unfortunately, many researchers clung to the idea of a single migration out of Africa, no earlier than 60,000 years ago, for too long. Finds such as a human presence in the Levant 100,000 years ago, for example, were dismissed as a single band of early humans that strayed too far from home and went extinct— in other words, an evolutionary dead end.

Today, however, writing in Science, researchers say that no one can ignore the preponderance of evidence. It’s time, at long last, to revise that tired old timeline of human migration.

The timeline they call for is one of multiple migrations out of Africa beginning perhaps 120,000 years ago. While some of these early explorations certainly failed and became evolutionary dead ends, others, say the authors, survived, not only spreading across Asia but interbreeding with Denisovans and Neanderthals.

Both the archaeological and genetic evidence support a large dispersal from Africa around 60,000 years ago, but it was by no means the first — or the last — to occur.

Behold the new map of human migration, approximate dates shown in thousands of years (ka):

Our species left Africa earlier — and more often — than conventional thinking once held. (Credit: C.J. Bae et al., Science (2017). Image by Katerina Douka and Michelle O’Reilly)

Our species left Africa earlier — and more often — than conventional thinking once held. (Credit: C.J. Bae et al., Science (2017). Image by Katerina Douka and Michelle O’Reilly)

The Point of Point A To Point B

Okay, so, science solved that, thanks, we know everything now, right? Nope. The new timeline for human migration still has some big holes to fill. Let’s start with where our species evolved.

Reading the map above, you might think the authors of today’s paper are suggesting our species evolved in Morocco 300,000 years ago. But the team behind the recent stunning Jebel Irhoud finds have stated they do not believe those early H. sapiens are directly ancestral to us. Pointing out other fossils believed to be archaic iterations of our species, such as a skull from Florisbad, South Africa, the researchers noted it’s more likely that H. sapiens were widely spread throughout the continent by the time a population reached Morocco.

Our birthplace remains a mystery. Also big questions: how the first modern H. sapiens left Africa and where they went.

The authors of today’s paper note that crossing from Africa to what’s now Yemen in the southernmost part of the Arabian Peninsula would have been no easy task. The strait between the two landmasses, currently about 12 miles wide, may have shrunk to a mere 3 miles wide during certain climactic conditions, but crossing it still would have required some kind of watercraft. It’s unclear whether the humans of 120,000 years ago could have built a raft or other basic vessel.

The Sinai Peninsula to the north, however, has provided a land corridor for the past few million years, and topologically at least appears to be the most likely route of dispersal — so it’s perhaps no surprise some of the earliest H. sapiens found outside of Africa are at Skhul and Qafzeh, just beyond the Sinai.

But early populations moving across the Sinai wouldn’t logically then take a sharp turn southeast, which is where the trail of artifacts and fossils seems to lead. Fragmented finds in southern and eastern Asia suggest that at least one group of early H. sapiens spread out along the coasts, eventually reaching Indonesia and Australia.

And some of these early exiters from Africa appear to have reached Siberia and northern China, interbreeding with other hominins along the way. The details, say today’s authors, remain to be worked out, as does our understanding of how these early populations on the move adapted to often radically different environments and ecosystems.

There’s Just One Little Problem…

Acknowledging that our Out of Africa saga has many chapters stretching farther back in time is an important advance for the field. But some paleoanthropologists are unlikely to sign on: that small but vocal group of researchers who advocate a regional model for our species’ evolution.

Modern humans, goes this school of thinking, are an amalgam of regional archaic H. erectus populations that evolved in situ and the much later H. sapiens interlopers arriving from Africa. Claiming that H. sapiens were already dispersing from Africa tens of thousands of years earlier, as this new timeline does, suggests that our species really does have a single homeland — Africa — and puts a crimp in the regional evolution model, which is a source of pride in areas of Asia.

So, while the conventional timeline that has dominated for half a century finally takes a tumble, don’t think that this is the end of the great debate regarding the early days of our species. There are doubtless more studies, more discoveries and more contention to come.

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  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    Give it up for Berbers’ ancestors, the kings of ka! ‘Tis a pity Spain did not grok intellectual evolution re the Moors, Catalonia excepted. “The Catalan region, the County of Barcelona, later joined the Kingdom of Aragon…and focused on what’s important: making money.” One appreciates the contemporary discord with Spain.

    • AQ

      What the fuck are you talking about.

      • OWilson

        He’s talking about how history got us to where we are today!

        Good “info” and “intel” in those old library books.

        And you don’t need cable or wi-fi!

  • FluffyGhostKitten

    ‘The authors of today’s paper note that crossing from what’s now Yemen to the southernmost part of the Arabian Peninsula would have been no easy task.’
    I don’t have access to the full paper, but shouldn’t that be crossing from what’s now Somalia TO Yemen? Yemen IS ‘the southernmost part of the Arabian Peninsula’, unless it was an island then, which I doubt.

    • GemmaTarlach

      Thanks for the close read, FluffyGhostKitten (Fluffy, if I may?)! This is what happens when I am multitasking and fail to catch typos. I will be updating the post momentarily.

  • Erik Bosma

    So how about “Peking Man”? Oh yeah, they were another species of Homo… We have a ridiculous way of always trying too categorize things because that’s how we find it easier to think, especially in the West. Homo isn’t a group of separate species – it is one species on a millions of years long spectrum with many many side branches. When famines of some description came along, some of these tribes discovered that the ocean could give them all the nutrition they desired and more. Enough of this fruit and roots and raiding carcasses. So, as their populations increased, they were forced to move since one spot could only feed so many people. They weren’t going back to the forests and savannas although some dumber ones probably did. But many followed the shorelines and set up camp where the sea could again provide. Do this for a few hundred thousand years and you’ve made it to Australia. They obviously also realized that rivers were a good thing. Not only fish but also fruit. Many turned up the river valleys and followed them one camp at a time. Now you can’t tell me that after all these years on the water someone didn’t figure out how to use a piece of wood to float across a river or a gulf. And you can’t tell me that others didn’t improve on this floating piece of wood. Voila… you’ve made it to Australia. You’ve made it to Polynesia and South America and possibly even Antarctica (poor fools). This all occurred in the past million years not the past 50 to 60 thousand. ‘Homo Habilis’, ‘Homo Erectus’, ‘Neandertal’, you name them… they were all humans. Just on a different scale.

    • Philip A. Rutter

      We’re on the same page- almost. Its the “species concept” thing. As an evolutionary ecologist, I’ve participated in “what is a species” and “is a species a real thing or only a human construct” arguments – for decades. Evolutionists still argue- but one thing that is clear is that the old idea that a “species” is static and does not breed with other species – is pure nonsense. All species are always changing; some very slow, some very fast. And hybridization with other species is ALWAYS going on- sometimes a little, sometimes a lot. Ma Nature is flexible as all get-out; and so are “species”.

      My own position- a species is a real natural “thing”, and represents a group of characteristics that are well adapted here, today. Crossing barriers evolve to keep that set of genes functioning together- because more of those progeny are successful; but when anything destabilizes in the environment, crossing barriers can become lower, as more of the rare hybrids start becoming more successful – voila, hybrid swarms and new species.

      I think it’s fair to call Neanderthals, for example, a different species of Homo. But the idea that therefore we couldn’t breed with them is ridiculous.

    • Chuck Johnston

      All good points.

  • Bruce Fenton

    60,000 years ago modern humans expanded from Africa into Eurasia, finally reaching Australasia…around 70,000 years ago. This study fails to address the situation but is a step forward for the consensus view. http://brucefenton.info/2017/09/08/the-colonisation-and-recolonisation-of-eurasia/

    • Armand Bourque

      So many interwoven populations well never know about,except by the most wild accident. Check out how the connection between the dine in u.s. southwest and the dine here in b.c. was discovered. At the chicago worlds fair!! Until then noone had a clue. Wild.

  • Jake Turk

    Instead of that unlikely sharp turn southeast after Sinai, how about following the Fertile Crescent all of the way to the Persian Gulf basin? Through most of the Pleistocene until ~15kya, the PGB was boggy but well above sea level and had a far more humid climate, plus it was the drainage basin for a single huge river (the conjoined Euphrates and Tigris) which flowed all of the way down through the Strait of Hormuz into the Gulf of Oman. From there, humans could’ve followed the Pleistocene coast of Asia east to the subcontinent, the Far East, old Sundaland, Australia, etc.

  • Philip A. Rutter

    A substantial part of the problem is the persistent use of the word “migration.” It’s absurd.

    It puts the idea into everyone’s head that early humans somehow “decided” to just up and move a couple thousand miles, next week. Didn’t happen. You will even find serious discussions among credentialed anthropologists that “this hominin could not have left Africa, because its legs are too short” – or some similar nonsense. Never mind that species from mice to trees somehow manage to “migrate” to new regions, other continents.

    We “expanded” our range- just as any other mammal does. Babies happen, conflict happens, the family/clan moves 30 miles away, and resettles. Rinse, repeat. With generation times of something like 20 years, there is abundant time for our ancestors to have just ambled and settled – not migrated like wildebeest or geese- across the globe.

    Once you get that scenario into your head- the picture looks very different; and far more compatible with known fossils. (And don’t forget- we’ve found maybe 0.1% of what fossils exist – which represent 0.00001% of the live population…)

    • OWilson

      Liberal education must provide fast if erronious answers to this Kardashian, Iphone generation who have been told that they are the pinnacle of evolution. The planet is dying in their paltry lifetimes too!

      It is settled science!

      (But the 4,500,000,000 year old mother Nature just smiles!)

  • C Armstrong

    We do need to update our migration theories.
    But, tossing Leakey’s (and his team’s) insights and discoveries would be a mistake.

    We can chart human evolution for millions of years in the Afar Region around many Leakey sites, and true there are other places with million, even close to 2 million years old, human cultural sites, NONE date as far back and as numerous as in Afar Triangle or Olduvai Gorge.

    H. sapiens archaicus clearly developed deep sea culture 200000 years ago in S Africa. There are clear and well documented sites over 100000 years in Australia, Indonesia, and China, cultures and people related to each other. There is a Leakey site that has a fire ring that dates to 130000+ year ago (and artifacts that are dated 200000+ BP) in S California, and if you check your archaeological news feed for this year and you were to visit the San Diego Museum and read the article published in Nature: University and state archaeolgists discovered a mastodon with worked bone and hammerstones and stone anvils, (enough to identify which hammerstone’s were used on a specific anvil) also 130000 years ago, and 160 miles South of Leakey’s California site.

    One assumption (and modern Archaeology is heavily based in culturally biased assumptions) that should be considered:

    a group of humans adapted to savanna and coastal life would not survive–as a group–trying to cross the Himalayas, and their connecting Mountain chains, which form an ecological blockade to early migrations. Only groups that have made mountains their homes with generations of adaptations would survive together navigating those mountains–they probably would not leave the mountains then for the savannas. The ancient evidence for humans in Indonesia, China, Australia, and San Diego (and they all share similarities in tech and choice of materials and choice of foods), the evidence does not point to a group among them that were descendant from groups migrating from extreme elevations and the ice of the Himalayas. In general, humans of any age, the majority are not attracted to ice living, which is why we do not see many sites linking cultures in Siberia, Alaska, and Canada.

    The common theory that is taught in major Universities (from class notes) and taught by published & well respected experts in the field of paleontology–the reason there are monkeys in Africa and S. America is the theory that a group was trapped on a natural raft of tangled reeds and roots that breaks off from the coast of one continent, and the monkeys survived the Atlantic crossing.
    When I took the class only a few years ago that was the consensus theory for monkey migration millions of years ago. My professor published a peer-reviewed paper (one of many) in a scientific journal on dental evolution of primates while I was taking that class on primates.

    This reaction to a 60000 year Out of Africa Theory is a knee jerk from archaeologists where many are only knowledgeable of their region or even their site’s background only. Archaeologists are very territorial and prefer to draw lines in the sand, both in time and space. Not all archaeologists just those that sit in their elevated offices and the same ones that are too old to do proper field work. Otherwise they would see the writing on the walls, literally.

    They get students to do the actual field work (and not asking for their student’s interpretation, only their [political] donors) then those archaeological directors, they draw the boundaries to interpret the data to support educational paradigms that their University(s) promote. I had a professor that was Native and studied the links between the Maya and New Mexico’s Chaco Canyon, he would teach in his class that his perspective was not adopted Nationally because if we give credit to the idea that Pre-Columbian Mexican culture is connected to areas in the USA then that would give Mexicans a cultural right to New Mexico and other states. From that professors perspective, there was an academic wall built to subvert research that interconnected Mexico and USA. I think we tend to forget that traditional Mexicans are Native Americans.

    I too am an archaeologist with geo-archaeology as my 2nd Masters. I will say that archaeology that is driven by accepted paradigm’s of regional (especially National) cultures, many times steeped in religious or ideological beliefs in stories told while they were a child of where we came from and how.

    Look I was raised in the Bible belt and had perfect church attendance growing up, mom was Sunday School Teacher. I believe in the teachings of the Bible, but I disagree with many politically driven interpretations. If you have to ignore science in order to be religious then you are useless to the future generations–to your kids. History will judge you based on that political agenda to put science down and force feed their specific brand of religion.

    Believing that the world is 6000 years old is just stupid (no really, shows no education based on facts), and not based on anything but an Arch-Bishops interpretation of all the lineages mentioned in Old Testament added up together on his pad of paper.

    If there was a H. sapien Adam and Eve then they lived in Africa a million years ago, if there was a cultural Adam and Eve then they existed in the Holy Land 100000 years ago, not 6000 years ago in Sumer and not 13000 years ago around the megalithic buildings of Gobekli Tepe, Turkey. If there was a human Adam and Eve, then they existed 7 million years ago (and likely much longer ago) in Africa.

    All nations want to prove that they are the 1st peoples, so regional independent evolution always raises its head in times of paradigm change.

    Current world level archaeology is not based in the scientific method–as stated in this article. We are here to explore the facts together and produce experiments together, not just try your best to shoot down new theories and so-called ‘facts’. We should not base the archaeology process on proving ideological assumptions at all costs.

    For example, there is no actual proof of a Beringia Migration 12000 years ago into Canada, there is proof against it–namely glaciers without life supporting “corridors”. Assumption based on cultural and ideological perspective of Europeans. The American Dominators wanted to show that Natives were interlopers that had wandered into a land, savages without culture, they new not what to do with and only within hundreds or maybe 12000 years (that was a hard sell–Natives owned America over 10000 years throws a wrench into selling genocide to a European citizenship in the 1500-1600s. They concluded the American Moundbuilder Culture were European because of the assumption that Natives did not have the technology. Largely a cover up, since Spain conquered the cities around Lake Texcoco in Mexico, the main metropolitan area was a bigger city than any Spanish city of that time. They had elevated technology, just not ships that could haul around horses in armor and tons of steel swords. The Spainish came prepared for implementing genocide and above all culture-cide. Only European religious perspectives would govern the savages.

    No archaeology is still where Galileo and Newton were when they tried to suggest methods akin to scientific facts. Religions of many conflicting regions control current world archaeology, but with the internet that is falling to the wayside. The scientific method is systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypothesis. Tests of hypotheses come from carefully controlled experiments that gather empirical data. As we can see in this article archaeology is trying to move into a scientific based process. A person needs to reproduce the fieldwork and the lab work and openly discuss all possibilities that explain the evidence before they shoot down–this is generally not done. Great claims require great evidence from the opposing view that proves the weaknesses of the scientifically produced data, not just saying: there is no evidence of culture in that area prior, so your data must be wrong. Which is what they say about California’s Leakey site and the new Mastodon site. They used to say that since the Bering Land Bridge only formed 12000 years ago that any evidence that concludes an older date is “obviously” crackpot theories. Only recently did Pre-Clovis sites start to be honored in Archaeology.

    The scientific method is not “come up with a hypothesis and then you and other researchers try to shoot it down..[then] you come up with a new one based on what you learned from destroying the old one”. This method will generally not produce a new theory, but reinforce old theories instead.

    This is however how archaeology sees the scientific method.
    Most of the time archaeologists from another region will not do the fieldwork or the experiments or the collecting of facts about a site, but they will be the first to shoot down ANY theory that deviates from their ideological perspective on the ancient world, generally simply “shooting down” by saying that stone tools could be produced by nature that resemble pebble tools, or they say that extreme claims require extreme evidence of which none will be enough for these University program “attack-dogs” defending their territory and their dated published articles, and not having to change their curriculum for established classes. Belief drives world archaeology NOT scientific method.

    There is evidence of Neanderthals reaching Islands. Many of the ancient sites away from Africa involve islands, but ancient archaeologist in general across the world will not even think to look for island evidence because they assume ancient humans were stupid and could not paddle tangled logs across a waterway. It is likely boats turned us into modern humans hundreds of thousands of years ago, possibly a million or more. But as an archaeologist I am supposed to whisper about this kind of evidence, or not mention it, because of world wide “consensus”. In general, I trust the field workers interpretations, over the accepted views of University leaders. Many governments have been accused over the last few decades of not letting this evidence into the public realm, sometimes they flood a site with water to stop excavations, erect military fences around the evidence, pour concrete over it, or they just send “attack-dogs” with a prepared lexicon after the offenders, which is generally a team of Ph.D.s attempting to practice the scientific method.

    This collapse of the 60000 year Out-of-Africa paradigm is long overdue, but we still originated in Africa as far as the recovered scientific evidence is concerned, we (our human ancestors) just left a million years ago, at least–60000 years ago is a joke, pushing that to 100000 years ago will not help the scientific process (when evidence is building for much longer), across the world there are sites well over that age that have cultural and advancing technological achievements that show up on other continents.

    For many years Directors of University programs and regional/state/national level programs, because the assumption is that culture does not extend beyond a certain time period into the past, then to dig further or publish evidence that contradicts the consensus, this would destroy careers. Directors would say, do not dig further down if you want a career in this region of archaeology.

    We will begin to see more and more evidence from sites where fieldworkers have been afraid to show their scientific conclusions for fear of ideological persecution.

    The world is changing, including the ancient world.

    We are the world, for a million years, at least. Boats make that understandable.

  • Welder Batista de Oliveira

    I have a hypothesis. As Neanderthals in several places in Europe got extinct possible due to human competition, several human groups who early left Africa might be got that same fate for the same reason – others homini competition. That would explain why we have found earlier out of Africa modern humans remains, despite most of today non african DNA relates to the 60 thousand years old migration

  • 6Kiazer6Souze6

    My DNA, of Armenian ancestry from National Geographic links my Y and maternal chromosomes to 2 US presidents (Lincoln and Jefferson), Benjamin Franklin, Akhenaten, King Tut, Genghis Khan, Tesla and the French and British Royals and many others. My grandparents were born only 30 miles from Gobekli Tepe. Gobekli Tepe is the source and cradle of civilization for all humanity and races.

    • Armand Bourque

      Hm. My advice,dont spout that patriotic nonsense if youre ever on a tour of peru…

      • 6Kiazer6Souze6

        Take your advice and stick it up your sphincter. Your advice and $3.50 will buy one a cup of Mediterranean coffee at Starbucks.

        • Armand Bourque

          Lol. Always takes a few generations to get out of a 3-goat village,eh?

  • stargene

    Hublin is quoted as saying, “..We did try to extract DNA but to date there is none,..”. Did they look for DNA in just bones or also teeth? If I under-
    stand correctly, teeth can function as better and more secure ‘containers’
    of ancient DNA.

  • Brian Bauer

    Why do all models suppose a migration west towards asia? I fathom it were possible at one time in the past to cross iceland to greenland by foot if not by ship.

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