In Brief
- At some point between 195,000 and 123,000 years ago, the population size of Homo sapiens plummeted, thanks to cold, dry climate conditions that left much of our ancestors’ African homeland uninhabitable. Everyone alive today is descended from a group of people from a single region who survived this catastrophe.
- The southern coast of Africa would have been one of the few spots where humans could survive during this climate crisis, because it harbors an abundance of shellfish and edible plants.
- Excavations of a series of sites in this region have recovered items left behind by what may have been that progenitor population.
- The discoveries confirm the idea that advanced cognitive abilities evolved earlier than previously thought—and may have played a key role in the survival of the species during tough times.
More In This Article
With the global population of humans currently approaching seven billion, it is difficult to imagine that Homo sapiens was once an endangered species. Yet studies of the DNA of modern-day people indicate that, once upon a time, our ancestors did in fact undergo a dramatic population decline. Although scientists lack a precise timeline for the origin and near extinction of our species, we can surmise from the fossil record that our forebears arose throughout Africa shortly before 195,000 years ago. Back then the climate was mild and food was plentiful; life was good. But around 195,000 years ago, conditions began to deteriorate. The planet entered a long glacial stage known as Marine Isotope Stage 6 (MIS6) that lasted until roughly 123,000 years ago.
A detailed record of Africa’s environmental conditions during glacial stage 6 does not exist, but based on more recent, better-known glacial stages, climatologists surmise that it was almost certainly cool and arid and that its deserts were probably significantly expanded relative to their modern extents. Much of the landmass would have been uninhabitable. While the planet was in the grip of this icy regime, the number of people plummeted perilously—from more than 10,000 breeding individuals to just hundreds. Estimates of exactly when this bottleneck occurred and how small the population became vary among genetic studies, but all of them indicate that everyone alive today is descended from a small population that lived in one region of Africa sometime during this global cooling phase.
This article was originally published with the title When the Sea Saved Humanity.
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27 Comments
Add CommentWebmaster: links to pages 3, 4 and 5 of this article don't work.
Reply | Report Abuse | Link to thisdon't work.
Who can contest or discuss anything that happened in the evolution 160000 years ago. Maybe one day we'll found there were iceman living and surviving in the hardest nothern hemisphere that were not perserved for the ages. I don't know, do you?
Reply | Report Abuse | Link to thisjohnmcragin
Reply | Report Abuse | Link to thisMan could stand up straight and walk on two feet a million years ago. This article doen't seem to jibe with the five glacial
ages and the intervening four interglacials (we're in the fifth
interglacial that follows the Wisconson ice age-- that's part of the rason for lobal warming). Is the Encyclopedia Britanica
all wet?
# I am a simple star gazer male 85, india. This is about the global effects of the periodic tilts of the earth globe affecting the climates etc: since 1950 it has occured to me that because the tilt of the earth changed to the present ursa minor polaris star, so before that, the poles,equator and the tropics were quite different, and the climates too naturally were not the same. that means that notwithstanding the glacial and other ages, different parts of the globe had been experiencing different climatic effects every time the tilt changed. now they say that Vega? will be the next pole star. will the tilt be gradual or sudden due to a krakatowa burst? a meteorite hit? or a shake up in the bowels of the earth, like even the magnetic pole reversing? naturally the human evolution corresponded to the changes in the tilt and the climates and glacial floods and sea rises, and so on.# There is an interesting observation in the ancient indian vedic lore that the star alpha? centauri [Agasthya?] was over the northern side of the globe India and it dipped south of the Vindhya hills range due to the south migration journey of the Sage Agasthya to South India from the North.===george pradhan,mb.
Reply | Report Abuse | Link to thisVery interesting, but in the same issue is an article by Mr. Shermer explaining why Homo Sapiens Neandertals and Homo Sapiens Sapiens are really subsets of the same species. Rather like the red, white, black, yellow, and brown races of today, Neandertals and Sapiens were able to interbreed, so therefore they were not different species.
Reply | Report Abuse | Link to thisFrom the time I first heard of Sir Alister Hardy's Aquatic Ape theory of human evolution, it simply made sense. The differences between humans and the other apes are too significant and too extensive to be dismissed. They are neither random and causeless, as some have claimed, nor supportable by any other evidence on the planet. Our species must have had a passage through an aquatic era as Hardy described.
Reply | Report Abuse | Link to thisBut external evidence has been painfully absent. Given the fluctuation of sea levels in the past few hundred thousand years, that is no surprise. It was also true that virtually nobody was looking. Yet with no paleo-anthropological evidence, there could be no substantiation of this radical idea.
Not only does the research by Mr. Marean and his associates reveal substantial evidence, but with a vengeance: a human population of a small enough size - that becomes the dominant variation! The pieces of diverse, independent sets of evidence that integrate into a bigger picture so well is a joy of science!
I have always believed that the rapid change of an ocean shore during the glacial swings would force the evolution of greater intelligence (for a species already fairly intelligent) in a way no other location can match. To know that 120,000 years ago, these people had art, technical multi-step know-how, and generational transfer of non-obvious knowledge should encourage everyone to give credit where it is due.
Sir Alistair had it right: we are the Aquatice Ape.
A quarter of million years ago H. sapiens knew that survival required location, location, location. And that location is waterfront. Where else does a species get the water, protein, fat, carbohydrates, and minerals necessary for existance in hard times? The individuals that made their way to the shoreline survived.
Reply | Report Abuse | Link to thisI might be so bold to suggest that the most hardy species are those in the tidal zone. Evidence being the multi-million year existence of the barnacle.
Poster note: My Sciam just got here yesterday and I haven't read the article yet. So, some of what I just wrote may have been addressed therein.
CAN WE STILL HEAR THE CRO-MAGNON MAN We can go back where Cro-Magnon lived http://independent.academia.edu/pfpuech/Papers
Reply | Report Abuse | Link to thisand have in some cases the possibility to look at individual stories in the “expression” of cognition, culture and cooperation.
The question addressed here concerns:
-the rites of passage, essential for the perpetuation and the strength of the clan;
-body ornaments and feminine sculptures with fertility traits:
-cave decoration including an animal (horse) within the close circle of our ancestors’ remains
Pierre-François PUECH pfpuech@yahoo.fr
Michael Shermer comes from the same world I live on. Curtis Marean is from some other world: different glacial epochs, evidence from genetics alone. What becomes of the data from European sites in the Neanderthal era in Marean's world? How about pre-sapients elsewhere?
Reply | Report Abuse | Link to thisYes! For those interested this theory and the ramifications of this article, please see Elaine Morgan's lecture on Ted, Ideas Worth Spreading, at http://www.ted.com/talks/lang/eng/elaine_morgan_says_we_evolved_from_aquatic_apes.htmled
Reply | Report Abuse | Link to thisAlternatively, simply Google Ted and search aquatic ape on the site. Excellent post!
I found the article by Curtis Marean to be very interesting.
Reply | Report Abuse | Link to thisHe mentions that glacial stage MIS6 ended about 123,000 years ago and this would have ended the genetic bottleneck he refers to in the article. I'm wondering if there was also another genetic bottleneck about 73,000 years ago when the Toba super-volcano erupted in Sumatra.
My congratualtions on Curstis Marean's article. Well done. It is thoughtfully organized and exhibits a respectable balance between data and interpretation. Further, his description of the application of experiment to answer archeological questions is illuminating. Also, the synthesis of a variety of data from disparate sources, i.e. genetic, archeological, climatological, et al, is an absolutely realistic portrayal of the multifaceted problems associated with human evolution. So, again, well done. However, I do have one concern. The resources listed under More To Explore are not accessible, at least some of them, without cost. Why?
Reply | Report Abuse | Link to thisIf human cognitive and technogical skills evolved during thie ice age, does that imply that Neandertals had much more mental development and technical skills than we've come to expect?
Reply | Report Abuse | Link to thisI've been a subscriber for more than 4 decades and still receive the print issue. I noticed in this article in the magazine that you ask for comments on this article. That seemed strange since, although I'm a longtime subscriber, I am not able to access the full article on your website.
Reply | Report Abuse | Link to thisI suspect you will find interesting a proposal that humans did not evolve from a single couple or even a single small group 200,000 years ago based on the fact that female mitochondrial DNA descends according to different laws than nucleus DNA in http://charles_w.tripod.com/eve.html . It also proposes that humans hybridized with other hominids they met as they migrated. If you see any errors in it, please let me know.
Reply | Report Abuse | Link to thisSincerely, Charles Weber
If you lok at p22 of this edition you will see that the latest science shews there was a migration out of Africa into Eurasia c.350kya before Marean's guesstimate.
Reply | Report Abuse | Link to thisThose precursors mated with other hominids (e.g, H. ergaster and/or H. habilis) to produce H neanderthalis and other H subspeciesin. When the Cro-Magnon parvenus arrived in Eurasia they mated with Neanderthals -- and probably others -- to produce modern humans. (About 4& of the modern Eurasian human genome is derived from Neanderthals).
Some 'modern' humans still exhibit such Neanderthalian traits as a squat, broadchested, hirsute and powerful torso, a broad face and nose, an occipital ridge, a prominent eyebrow ridge, etc. Cro-Magnons tend to be more psyically gracile overall and less hirsute.
Moreover, it seems impossible that Cro-Magnons got from Africa to E Asia and beyond without interbreeding, on route, with some of the half dozen or so other hominid species living in Eurasia between 150-4okya when the ancestors of modern Australian aborigines arrived on that distant island-continent.
It looks as if Marean has beeen so absorbed in his own local archaeological work that he has failed to keep abreast of the latest developments elsewhere in the world.
If the Neanderthals could adapt to living in a frozen Eurasia there seems no reason why the warmer climate of S Africa shouls have caused a problem for the H subspecies living there.
There may well have been an evolutionary 'bottleneck' in Africa c,195kya, but that doesn't mean that the same occurred in Eurasia or elsewhere. Perhaps there was another cause for the 'bottleneck', if it really existed. Maybe, there is a gap in the archaelogical record in Africa due to geophysical events there that have obscured the evidence.
Why, if h. neandertal already existed in Europe, Asia Minor and Asia during the period when our supposed h.sapiens ancestors were inhabiting their S. African caves, did SA picture an imagined cave survivor on the magazine cover with the brow features of h. neandertal? Can't the editors break away from the old worn-out stereotype of cavemen having to have beetlebrows instead of the gracile features of our ancestors?
Reply | Report Abuse | Link to thisI read with great interest your two articles on early man in the August issue. But I cannot help but note that there seems to be a conflict. The feature (cover) article talks about the survival of the human species being a lucky happenstance in the southern tip of South Africa saved by the sea creatures during the worst of the ice ages about 195,000 to 123,000 years ago. It states that this is why there is a "population bottleneck" with the human species. We are fortunate that this and a handful of regions are all that could have supported hunter gatherers during this cold period.
Reply | Report Abuse | Link to thisI must ask then, how does this theory explain how the Neandertal were able to exist in the northern European areas during this same time frame to mingle with the modern humans when the ventured out of Africa 80,000 years ago, as the SKEPTIC piece discuses in the other article in this same August issue? If humans had to just barely hang on along the souther coast of South Africa and eat seafood (because all other land animals were basically gone), what did the Neandertals eat...and how were they able to survive this same ice age up north? If they did survive (and evidence is they did, based on the SKEPTIC discussion) it seems that other pockets of humans were able to exist in possible many other locations. This would bring into question the Feature article's main argument that South Africa or other isolated regions like it, was where we almost became extinct. Or am I missing something?
Joe Wallace
Austin, Texas
This is one of the best long articles I have read in a while. It revealed new ideas to me and is easy to follow. If the human race did pass through a period where only a few survived, and it occurred during a period where human diet was altered and constrained, perhaps the forced altered diet led to other changes such as a larger brain and higher intellect. Perhaps that ice age is a prime contributor to directing human evolution to what we are today.
Reply | Report Abuse | Link to thisPrevious reviewers have tellingly underscored the conflict between Mr. Marean's theory and recent work on Neandertals. I wish to point out further weaknesses in this article:
Reply | Report Abuse | Link to thisMr. Marean states that "mussels, limpets and sea snails live in the treacherous intertidal zone, where an incoming swell could easily knock over a hapless collector." He continues that it's only safe to harvest them during the exceptionally low spring tides. The upper left photo (page 58 of the print edition), however, dramatizes the "risks": those 1/2" swells look pretty scary, don't they?
Mr. Marean's contention that the people living in cave PP13B required a sophisticated lunar calendar to schedule their trips to the water, is, well, lunacy. He's postulating humans who were intelligent enough to construct such a calendar, but too stupid to just wait for a calm day and harvest at any ordinary low tide? And it's not like the shellfish were scarce, or only accessible at an extreme low tide. The same photo's caption reads: "Shellfish . . . abound year-round in rocky intertidal zone."
Suppose somebody got hungry but forgot to check their lunar calendar and arrived at the water's edge at mid or even high tide. They're smart enough to create such a calendar, but too dumb to just reach down into the water for the bounty a couple of feet below the surface, or heaven forbid dive down and snag some mussels off the rocks?
He also makes a big deal of how far inland the cave was, perhaps two to five kilometers from the water's edge. This is supposed to be a challenge for humans whom we're told at those times routinely traveled 10 miles or more a day? Any decent modern runner can knock off the 10 km round-trip in under an hour. Even over rough ground, I'm sure there are plenty of kids in nearby present-day villages who could do it.
Elsewhere in the article he makes the point that human groups followed the water as sea levels changed, dwelling always near its edge. For all anybody knows, the water was lapping on the rocks 20 yards from that cave at the times when it was occupied.
Bottom line: much of Mr. Marean's work and conclusions are intriguing, but his contention that the cave dwellers used a sophisticated lunar calendar is an egregious example of massaging the rather tenuous facts (caves with shells, source of shells somewhere relatively nearby) to bolster his theory that these earlier members of our species were every bit as intelligent as modern humans. I actually happen to like that concept, but his specious line of reasoning fails to prove it.
On page 60 of the print edition is a photo of stone tools found in PP13B. The caption states they "include sophisticated implements such as microblades which would have been attached to a wooden shaft to form projectile weapons." Is the author postulating that these people possessed bows and arrows? Come on! If they did, though, surely they knew how to notch the arrowheads to more securely attach them to shafts. Lacking bows, as seems far more likely, how did they manage to propel that little affair? Toss it by hand?
Reply | Report Abuse | Link to thisSo what good is a tiny flake of stone (in the photo they're not even pointed!) attached to a small stick? A child's toy at best. I'd like to know the opinion of someone knowledgeable in knapping, but to my skeptical eye these "microblades" are merely flakes discarded by the tool-maker as useless.
As a child of eight visiting near the English coast I was completely aware that the tides came each day about an hour later than the day before. I was completely unaware that the moon had anything to do with it, and so, I suspect, was my grandfather.
Reply | Report Abuse | Link to thisWe may reasonably deduce that ancient woman knew that it was easiest to gather shellfish when the tide was down. Period. Any speculation about cognitive abilities beyond that is just wild.
The logic seems wrong when the author reasons from the narrow genetic diversity of humans, compared with other species, to a "bottleneck" of a few ancestors.
Reply | Report Abuse | Link to thisFor a long time our species has adapted to environmental changes by changing ways of producing food and other necessities. Other species adapt to environmental changes by biological change, typically leaving the old population in one niche and a population with different genetic makeup in another niche.
The comparison between species, therefore, does not support the historical "bottleneck" moment as the source of relatively less DNA variation.
Was Europe under ice during MIS6? If so, were the Neanderthals hibernating for millenia before the invasion of Homo Sapiens?
Reply | Report Abuse | Link to thisNJB
The article "When the sea saved humanity" proposes that our ancestors were driven out to the coast by climatic changes. The hypothesis that the interior plains became uninhabitable resulting in a crash of the population of Homo sapiens would require a corresponding crash in the populations of all the animals they hunted. Otherwise, why would they have left?
Reply | Report Abuse | Link to thisAn alternative explanation for evidence of early humans on the coast is that this is where they had been living all along.
When Homo erectus first started hunting on the savannah, the strongest groups would naturally have occupied the best territory, with the weaker ones pushed out to peripheral areas, including the coast. Scavenging for whatever they could find, these groups would have needed intelligence rather than strength to survive.
Other conditions would have been conducive to changes leading to modern humans:
A coastal environment is much more suitable for experiments with fire than the dry savannah.
Silence is essential for hunting and for evading predators such as lions, whereas on the beach audio communication is advantageous.
A coastal environment would favour those individuals who could catch fish, swim and hold their breath, an essential prerequisite to speech.
I suggest that over a period of several hundred thousand years, the coastal version of Homo erectus developed distinct abilities including the use of fire and speech. This gave such advantage that our ancestors were eventually able to re-occupy inland areas. The climate changes mentioned in the article would have assisted in this process, but would not have been the main cause.
We modern Humans are becoming so pompous. Does anyone believe we can know with any certainty that there were only a few (hundred) breeding pairs of our ancestors, in only one area, 200,000 years ago? Quite a theory.
Reply | Report Abuse | Link to thisIt is generally thought that long before bows, a notched wooden throwing implement (atl-atl)was used to propel a spear. This extends back to Paleo period (15,000 BC)hunting for large mammals, and probably much earlier. Those spear points are very large and finely done. Bows and arrows came much later, we think, but who really knows. You are correct, the points shown look quite simple, and those tpyes were produced up to modern times, by quickly knocking a single blade off of a pre-shaped core of flint or obsidian.
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