July 6, 2007...4:45 pm
Mount Toba Eruption - Ancient Humans Unscathed, Study Claims
At about 74,000 years ago, Mount Toba on the island of Sumatra erupted in a massive explosion that supposedly rocked the Middle Palaeolithic world to its very foundations, bringing contemporary human populations to their knees, reducing the global population level to around 15,000 individuals, thereby precipitating a so-called bottle-neck of human evolution, as proposed by Stanley Ambrose, from the University of Illinois at Urbana-Champaign, discussed in this BBC News
article from 1998, and in an essay at the Bradshaw Foundation, in the same year. However, recent discoveries made by Michael Petraglia, from the University of Cambridge, have now cast doubt on this theory…
(the team)…found the stone tools at a site called Jwalapuram, in Andhra Pradesh, southern India, above and below a thick layer of ash from the eruption of the Toba volcano in Indonesia — an event known as the Youngest Toba Tuff eruption.
The tools from each layer were remarkably similar, and Petraglia says that this shows that the huge dust clouds from the eruption didn’t wipe out the population of tool-using people. “Whoever was there seems to have persisted through the eruption,” he says.
This is the first archaeological evidence associated with the Toba super eruption, says Petraglia, and it contradicts theories that the eruption had a catastrophic effect on the area that its ash blanketed.
Following this eruption, a phase of dramatic global cooling ensued, evidenced by a 6-year global winter, which in turn was followed by the onset of the Würm glaciation event. Petraglia proposes that only modern humans could have survived such an event, giving as his evidence the supposed similarity of the lithic assemblage, and purported others, which he claims correspond with those found in Africa dating to around 100,000 bp, by which time modern anatomically modern humans had been extant there for some 100,000 years.
Petraglia thinks that modern humans — rather than Neanderthals or other hominins — are the only species that would have been able to persist through an event as dramatic as the Toba eruption. This theory will spur much debate, he admits, because modern humans were not thought to have reached India, from Africa, so long ago. “It’s controversial,” says Petraglia, “but it makes a lot of sense.”
Petraglia and his team compared the tools they found to others from Africa from different periods in this week’s edition of Science1. The Indian tools look a lot like those from the African Middle Stone Age about 100,000 years ago, when modern humans were thought to have lived, he says. “Whoever was living in India was doing things identical to modern humans living in Africa.” Neanderthal toolkits found in Europe are very different, he says. This is more evidence, he says, that the plucky ash-covered inhabitants of Jwalapuram were modern humans.
However, we know that modern humans weren’t the only individuals capable of withstanding sudden and extreme climate change, as Eurasian Neanderthals lived through the Riss glaciation which occurred from 180,000 bp - 130,000 bp, and they also survived the Mount Toba event, regardless of its supposed global impact. It’s possible too that Homo erectus lived on as late as 50,000 bp in Asia, and if Homo floresiensis turns out to be a genuine new species, they too survived this event (n.b. - but see this latest update from John Hawks, which I’ll attempt to address later)
Moreover, lithic assemblages, whether in India, Africa or Europe don’t always indicate exactly which species of Homo may or may not have been responsible for their manufacture, as pointed out by Stanley Ambrose…
(who) disagrees with Petraglia’s conclusions. “It is highly speculative to say the eruption had no impact,” he says. Ambrose argues that Petraglia’s sample size is too small to make proper comparisons with other tools. And, he adds, “stone artifacts cannot be used to differentiate Neanderthals from African moderns.”
…which raises the question of exactly which species of Homo would have been living in India at the time of the Toba event. At 74,000 years bp, it is generally assumed that anatomically modern humans were still resident only in Africa, from where they would emerge at around 50,000 bp to commence their purported total replacement of all other species across the globe, culminating in the extinction of the Neanderthals at around 24,500 bp.
However, we know this can’t be true, because as John Hawks points out in his post on this topic, Australia was populated by moderns by at least 50,000 bp, and quite possibly even earlier still, at around 60,000 bp, depending on one’s interpretation of the widely different/wildly conflicting dates given for Mungo Man. And if Homo erectus managed to navigate the open seas to Flores at 840,000 bp, it would appear that modern human behaviour is a great deal more ancient than in its comparatively youthful Middle and Upper Palaeolithic claimed origin, meaning that theoretically any species of human from Homo erectus up to and including early Homo sapiens could have prevailed in a post-Toba environment.
But even more crucially, there is evidence of modern and symbolic behaviours coming out of India at dates far earlier than these Middle Palaeolithic dates, as indicated by Robert Bednarik’s paper from here, in which he details what may be evidence of Indian palaeoart dating back to around 300,000 bp, making it roughly contemporary with ostrich shell disc beads from Lake Fezzan in Libya.
On a very generalised basis, it could be argued that there were constant pulses of emigration from Africa to Asia, dating back from the Acheulean, through the African Middle Stone Age, as indicated by the purported modern survivors of Mount Toba, followed by others at around the Middle/Upper Palaeolithic boundary of Eurasia, and especially western Europe, plus many other African exodus which have so far remained undetected.
On the other hand, others might argue that what we are seeing here is evidence for various multi-regional events, in which local populations in Asia and Africa evolved in some kind of parallel, possibly mediated by more or less frequent encounters and genetic exchange between the two populations over the course of hundreds of thousands of years.
But until fossil evidence is retrieved from sites like Jwalapuram, we will have no clue as to the true identity of the makers of the stone tools and other sites alluded to by Petraglia - even if, and when fossil remains are recovered, further clarification as to the geographical origin of those specimens may be in need of yet further clarification. (TJ)
see also: Early Indian Petroglyphs project
44 Comments
July 7, 2007 at 4:58 pm
[…] Mount Toba Eruption - Ancient Humans Unscathed, Study Claims At about 74,000 years ago, Mount Toba on the island of Sumatra erupted in a massive explosion that supposedly rocked […] […]
July 8, 2007 at 11:37 am
It’s nice to see that anthropologists appear to be more willing to state publicly what has been obvious to the interested general public for many years now: The commonly presented model of early hominid/human migration patterns is overly simplistic in the extreme and in at least some respects completely wrong.
July 10, 2007 at 8:30 am
Thanks Steve, although I should point out that I’m not anthropologist in the traditional sense as I’ve never studied the subject academically, so I can’t claim to speak for the profession as such - however, there is more data being published that indicates (to me at least) that the African exodus total replacement model of the Middle/Upper Palaeolithic, supposedly giving birth to modern mankind, does itself need to be replaced completely, and moreover the whole idea of archaic humans being inferior to ourselves, H.Sap, is seriously flawed.
Tim
July 25, 2007 at 8:31 pm
From the studies I have seen, compare it to the Mt. Tambora eruption that was 28 times smaller than Mt. Toba. The destruction of archaic humans would be unavoidable. In 1816, the “year without summer” untold hundreds of thousands of humans died. The eruption would have wiped out all but a few thousand very tough Neanderthals.
Mt. Toba dropped the planet into a 5 year winter, and continued with a 19,000 year ice age. Ancient archaic species that resembled us, and who at that time were hunter-gathers would have be wiped out.
The Cambridge University study released on May 8th of this year confirmed that the DNA of the New Guinea and Australian people are all decedents of the North Africa group coming out at the end of the ice age about 55,000 years ago. The ending of the Mt. Toba ice age.
The whole idea of archaic humans being inferior to ourselves is without doubt true. The modern humans coming out of Africa migrated as hunter-gathers down the sea coasts through to Asia. In 47,000 years we have gone from sitting in a cave around a fire to landing modern humans on the moon. The archaic humans had a much longer time frame than that to exist and never progressed farther nor improved their living habits as shown by their tools and living conditions.
There is no convincing proof other than a few tools above the ash that any archaic humans survived the eruption.
The archaics barely changed the way they made a tool in a hundred thousand years. We change clothing styles every year. There is no doubt they were inferior, that is made plain just by reading this computer.
Ken
July 26, 2007 at 2:38 am
Hey Ken. You say:
The eruption would have wiped out all but a few thousand very tough Neanderthals.
But Neanderthals lived miles away, in Europe. And yet pre-modern humans survived in Southeast Asia, much closer to the eruption. How do you account for that?
July 26, 2007 at 8:34 pm
What pre-modern humans are you speaking of? I know of no findings of an pre-modern humans camps or living areas found after the Toba eruption except for a few tools that are argued were pre-human above the ash. That is the only evidence I am aware of, and that is disputed. As I said, as a hunter-gather species with nothing to gather and no way to store food, the likelyhood of survival was almost non existent. If that were not so, the DNA findings would not indicate that every person alive today is decended from appox. 10,000 modern humans out of North Africa. It would confirm that Southeast Asia was empty as they migrated out of Africa and down the sea coasts. See the May 8th study finally released by Cambridge University on the DNA studies confirming that we all came out of Africa about 55,000 years ago. The 10,000 DNA combinations have been known for sometime. We are all kin.
July 26, 2007 at 8:40 pm
Actually, if you will look at the Bradshawfoundation.com it will explain with much more numbers and facts than I can put on this post. Ken
August 1, 2007 at 9:33 pm
The new Toba discovery looks to be extremely important:
1. If Petraglia et al are correct, it would appear to be the earliest archaeological evidence for modern humans in that part of the world and therefore a huge boost for “Out of Africa.”
2. It also creates some problems, however, because some sort of bottleneck is needed to explain all sorts of things that need explaining — such as discontinuities in the genetic evidence — also human phenotypic (and cultural) diversity generally. If the Toba explosion failed to generate a catastrophe sufficient to produce such a bottleneck, then something else must have done the job — a Tsunami perhaps.
3. If, as Hogan states, the eruption would have produced a truly monumental catastrophe, then perhaps the only logical explanation is that small amounts of exceptionally hardy individuals might have survived in scattered areas throughout Asia. That too would have produced a bottleneck. I guess we just need to wait and see what other types of evidence will be found associated with Toba tuff.
4. As far as hominids surviving in East Asia is concerned, the prevailing winds appear to have been northwest, which might well have spared any humans east of Myanmar.
August 2, 2007 at 2:13 pm
Hi Victor - thanks for your comment - Mount Toba seems to be one of those ongoing mysteries, with no-one really sure about its actual impact on the human population - a few years ago it was thought that virtually the entire human race at the time was almost brought to its knees, causing the so-called bottle-neck, although people like John Hawks dispute this idea - plus, those who opt for the ‘Out of Asia’ paradigm could equally take heart from this story, claiming that the modern tools were part of a regional development - some fossil specimens in context of the site would certainly tell us a thing or two, though whether the picture would be conclusively clarified is anyone’s guess…
August 4, 2007 at 6:47 pm
I think we should put much more study into the effects on humans that Toba caused than has been done. We have basically three species of hominiods before Toba. After Toba, we have a species that arises that is similar to the others, but the brain is different. The species before us had hundreds of thousands of years to develop and simply didn’t. Some of them made their tools the same way for a hundred thousand years.
In about 47,000 years, modern humans circle the globe, killing everything in their way that was dangereous. Giant Cave Bears, Saber-Tooths, Cave Lions, you name it, it’s gone. We let live the dangerous animals we do now out of guilt. Something the other species could not ever accomplish, or even attempt.
50-55,000 years after coming out of Africa, the modern humans land a man on the moon. Something radical happened. What is what we should be looking for. Will we ever find out? Who knows? Not me, but it is the direction for the right people to be going to look closely at. If the Cambridge Univerisity study of May 8th is correct, every person living today came from those migrations. The total DNA combinations come from 10,000 modern adult humans, there is some explaining left to do. The studies I saw would not produce a bottleneck that changes our nature from them to us. We are not them. We adapt, we change, we wonder, we build, we kill our own species in quanity. Something no other species on Earth does. I wonder who is studying this, if anyone? Everyone has the grant money for the DNA studies, but still not understand how we became who we are. Ken
August 5, 2007 at 2:02 am
Ken, you comment,
You leave out another thing they killed that may or may not have been dangerous: the other human species they ran into.
August 5, 2007 at 9:25 pm
Terry T,
If you look at the last paragraph, I noted that we change, adapt, we wonder, we build, we kill our own (I meant humans here) species in quanity. You just missed it, or I wasn’t clear what I meant.
That is what is interesting to me. We are the only species that kill their own in mass quanities. Why is that? What makes us do what other species will not do? Some fight when they mate, and sometimes, but not often it is fatal. But they don’t line up and kill each other in mass quanities like we do. There has never been a sentient being on this planet that we know of.
Evolution has played a trick and produced a species that may wipe itself out because it is so much more intelligent than any other species known. Perhaps so intelligent it destroys itself. That doesn’t sound intelligent, but we are what we are. The most savage, cold blooded killers that have ever walked this Earth. We have no remorse, and for most or all of our history it was kill or be killed by other humans.
We make the dinosaurs look like new born kittens. They just killed for food or grazed, mated and died. Up against us, they would with no doubt, have not a chance to live. We would kill each other for the chance to kill them all. We kill for many other reasons than food. How did we get to this point? Wouldn’t it be interesting to know those answers? Ken
August 5, 2007 at 10:17 pm
Yes. We are an interesting species.
August 5, 2007 at 10:38 pm
Ken. I just went onto your “Veritas” site. You list a few “truths” but a couple of them are actually wrong.
Java man is now thought to have survived until perhaps as recently as 40,000 years ago if not more recently. The so-called Hobbits also survived until even more recently. Humans also survived in Africa.
That’s just the mitochondrial DNA, our mother line. Its common origin seems to be at least 150,000 years ago. The Y-chromosome, our father line, has a much more recent common origin. The two lines are fairly independent of each other. Therefore other DNA from previous species may easily still survive today.
Human ancestors have survived continuously in Africa since we first separated from other apes. Changed through selection over the ages of course, but there’s actually no sudden change within Africa we can use as a cutoff point to define modern humans.
August 6, 2007 at 2:21 pm
Terry,
Thanks for looking at the website. I should have updated it by now and have not. The information I had five years ago has changed. We still believe that 10,000 modern humans are all the combinations we decended from. I have since seen some sites in far eastern asia that could be survivors of the Toba eruption. So a small number could have survived the eruption, but it takes a minumum of 500 different DNA combinations to keep the group from having serious genetic problems and dying out. (Some claim 5,000) We don’t know how long they would have lasted. The Amish are going through some of those problems now. The study of Picarn Island, where the H.M.S. Bounty landed is a really sad tale of not enough combinations. There seems to be no tell tale signs of continued pre-modern humans after the eruption, even in Africa until about 15,000 years after the eruption. Except of course the Neanderthals until I saw the tool finds in Asia above the ash. That debate is still going on. There were no dated material that I could find at the time. I did look and asked everywhere. Nothing. Things do change though, and those statements could be wrong.
What I do stand by is the conclusion that we all decended from those 10,000 adult modern humans, and that they were for some reason either much more intelligent (I believe that) and/or they were much more violent to each other and anything they felt was a threat. You have to remember what I wrote is fiction, and all “facts” are subject to change as we continue to study the evidence. It is just a story, but I used the “facts” available to me at the time. I should update my website. We did apparently appear out of thin air, simply because none of the other species could do what we do. There is no sign of gradual improvements in humans. These 10,000 appeared just as we are today. It is a big mystery as to where they came from and why all of a sudden. In the blink of the eye of time so to speak. Thanks for pointing those things out and I will update my site to reflect the new findings that have been made. Just remember, underlying all that, it is just a fiction book. I meant it to be a interesting alternative to creationism and evolution. We are here for a reason, just not what we have come to believe we are here for. The books reveals there is a very good reason we have no contact with other world civilizations. It’s just a story.
Regards,
Ken
November 6, 2007 at 4:52 am
Petraglia’s team finding does not prove that YTT did not have a devastating effect as suggested by Professor Ambrose. It only tells us that the population that settled in that area made the same tools or similar tools as the population before the YTT event. Why are people so skeptical about the YTT theory? Mass extinction due to volcanic eruption has happen before. One such example is the Siberian Traps that is thought to have caused the Permian mass extinction 250 millions ago. But Ken posed a different question. How did we come to be a species that kills its own kind on a large scale? On that count, humans is not unique. We can see that ant colonies wage war over territory. It may be between different species of ants but they fight to the end nevertheless. But with the level of intelligence humans possess, the destructive nature of our specie can be extreme. New technology and old habits is a devastating mixture. Ken also ask another question, how did the human specie remain unchanged in the stone age for hundreds of thousands of years and in a relatively short time in geologic terms got to the moon? This may sound outlandish but there seem to be evidence that this planet may have had extraterrestrial visitors in the past. If we are to consider Darwin’s theory as true. Then, we must ask, what biological advantage is there in the evolution of golden hair and bright blue irises?
November 6, 2007 at 11:25 am
I won’t comment on the “extraterrestrial” angle, but do want to add a few more cents worth of commentary regarding the Toba findings. The evidence Petraglia found by no means tells us that the eruption of ca. 70,000 years ago would not have had a devastating effect on any humans living in India at the time. We are talking, after all, about an 8 foot thick layer of volcanic ash spread over many thousands of square miles! If Petraglia found very similar stone implements both above and below that ash, what that tells us (assuming he didn’t get sloppy) is that SOME humans in that place somehow managed to survive the catastrophe. Hawks wants to believe these findings put the bottleneck theory to rest, but they most certainly do not. An event of that magnitude would certainly have led to population annihilations and/or bottlenecks in all parts of the affected region. The very meaning of a bottleneck requires at least a few survivors, after all.
What Petraglia’s findings seem to indicate, if his comparisons with African artefacts are to be taken seriously, is that “modern” humans were in that area during the time of the eruption. If his interpretation is correct, then “bottleneck” theorists like Oppenheimer must be taken very seriously indeed.
What Ambrose wants to believe is that the Toba eruption precipitated some important and fundamental change among humans living in Africa, a change responsible for the Out of Africa exodus and the morphological diversity we see among humans in various parts of the world today. I’ve never been able to make much sense out of that. First of all, Toba is nowhere near Africa. Secondly, all the characteristics of modern humans, including language, are found equally througout both Africa and the rest of the world, so it would seem rather pointless to associate some sort of fundamental intelligence spurt with the Out of Africa migration. Finally, if human morphological diversity originated in Africa, why do we find so much of it outside of Africa?
If Toba precipitated modern human diversity, then modern humans would have had to be living downwind of the eruption when it occured and would thereby have been affected by at least one and possibly more bottlenecks. Humans living to the east of Toba would NOT have been so affected — and would still resemble Africans, which so many indigenous groups in SE Asia and Melanesia in fact do.
Petraglia’s findings reinforce such a theory, contrary to what individuals such as Hawks might want to believe.
November 7, 2007 at 1:15 am
Victor wrote, “What Petraglia’s findings seem to indicate … is that “modern” humans were in that area during the time of the eruption”. This puts modern humans in India by 70,000 years ago. This makes an occupation of Australia by 60,000 years possible but contradicts many dates given for a single out of Africa origin. In fact the greatest difficulty with the theory is that no-one can come up with any real evidence for a date. A date of 40,000 years seems consistent with a possible movement INTO Africa though. And we know from fossils that modern-looking humans had reached the Middle East by about 90,000 years ago. They were then replaced there by Neanderthals until about 60,000 years ago, so perhaps the single origin theory should be more like a double origin theory.
Free Citizen wrote, “what biological advantage is there in the evolution of golden hair and bright blue irises?” It would pay us to remember that there characteristics are usually associated with pale skin. In fact people with that pale skin become darker under the influence of summer sun. How would we explain any other creature that changed from white to brown with the seasons and had pale coloured eyes? Do we perhaps assume humans obey a different set of biological rules to the rest of nature?
November 7, 2007 at 6:31 am
The first paragraph of Petraglia’s report ends with this sentence, “Its impact on Earth’s atmosphere and climate (5–7) and on local animal and plant populations remains a matter of contention.” Note how a biased view was exhibited before the piece began to describe the findings at the site? The report offers no explanation to counter the evidence of ice core oxygen isotope indicating that after the YTT event, the earth did experience the coldest temperatures in the last glacial period for a thousand years. The piece also does not state with a higher degree of accuracy how much immediately after the YTT it is implied that humans were present in the area. That was and still is tropical area. Flora and fauna would have recovered relatively quickly after the ash had settled. It would take no more than a few generations for humans to reach there from Africa. But if Petraglia’s team were to find stone tools in the ash layer itself, that would reinforce his argument further. However, that is not the case. So, his findings proves nothing.
As regard to TerryT assertion about association with pale skin, this argument doesn’t hold much water. If skin can have pigment that turns darker with the summer sun, why does the hair not turn darker too during summer? Unlike humans, polar bear hair do change from white to yellowish during summer but the skin is black all the time and the eyes certainly isn’t blue. What makes humans so unique that it should have a different evolutionary trait apart from other animals? There shouldn’t be and there is no satisfactory answer to explain the need for golden hair and blue eyes.
When General MacArthur landed on some remote island in the Pacific with his fleet, the aborigines thought he was god. Is it so hard to imagine that some time in our ancient past, similar things could have happened?
November 7, 2007 at 7:58 am
TerryT wrote: “In fact the greatest difficulty with the theory is that no-one can come up with any real evidence for a date.”
It’s true that there has been no tangible evidence for an “Out of Africa” migration date — until now. Petraglia’s research does in fact provide us with evidence consistent with the presence of “modern” humans in India at the time of the Toba explosion. He could be wrong, of course, and the tools he found could be the product of some type of homo erectus or neaderthal population. If he is right, however, then the stone tools found beneath the Toba ash would represent the first solid evidence of “modern” humans in that region at such an early date.
As far as the earlier presence of modern humans in the Middle East, ca. 90,000 bp, the genetic evidence indicates that this lineage did not survive. There may indeed have been several “Out of Africa” excursions, but apparently none of the lineages survived — and only one left tangible evidence, in the form of fossil bones.
The preponderance of genetic evidence tells us there was one and only one Out of Africa migration that produced the Asiatic, European, Oceanic and American populations extant today. As for the date of that excursion, it’s hard for me to understand why so many anthropologists have been so conservative with their dates. 40,000 bp is way too late to account for either Europe or Australia. 50,000 bp is still too close to the dates for the earliest occupation of Australia. 60,000 bp could be right. But Petraglia’s evidence suggests an even earlier date. Why would that be so difficult to accept?
November 8, 2007 at 2:59 am
Victor askes, “Why would that be so difficult to accept?” It’s not. But even earlier is even easier to accept. After all just because the Y-chromosomes outside Africa probably go back no more than 60,000 doesn’t say anything about mitochondrial DNA. In spite of popular beliefs the two lines are remarkably independent. Mitochondrial DNA outside Africa could easily go back more than 80,000 years, close to “the earlier presence of modern humans in the Middle East, ca. 90,000 bp”.
I’m afraid it’s impossible to conceive of any sort of genetic evidence that could prove “there was one and only one Out of Africa migration that produced the Asiatic, European, Oceanic and American populations extant today.”
Free Citizen asked, “What makes humans so unique that it should have a different evolutionary trait apart from other animals?” That was my point. The explanation for seasonal colour change is likely to be the same for humans as for any other animal or bird from the same region. Not necessarily the same mechanism of course. Hence the hair needn’t change colour. Polar bears live much further north than humans would have been able to until they had invented warm clothing.
November 8, 2007 at 1:55 pm
Terry — it’s important to realize that the dating of genetic markers is extremely iffy and vague, so the 60,000 bp figure for Y may well be off by a considerable amount. mtDNA can be traced much farther back, apparently, but that has no bearing on Out of Africa. African “Eve” was born in Africa sometime between 150,000 and 200,000 years ago, apparently. And the “founding’ markers for Eurasia are also located in Africa way back when. Forget about the Middle Eastern migrants, their line seems to have come to dead end, there’s no evidence of it anywhere else.
And yes there IS evidence supporting the “one and only one” Out of Africa migration. At least as far as mtDNA is concerned, I’m not sure about Y. All the mtDNA of all living non-Africans can apparently be traced to a single individual. If multiple OOA lineages had survived, the human mtDNA genome would look different. That’s my understanding, at least.
As far as blond, blue-eyed, and like that, I see no reason why these have to be adaptations. They could also represent mutations that survived and then prevailed purely by chance, as the result of a severe population bottleneck, most likely in Europe, maybe due to Ice Age conditions. I see no advantage in blondeness or blue-eyedness. Black people survive very well in all parts of Europe as do light skinned people in Africa. Humans are remarkably adaptable and always have been.
November 8, 2007 at 9:04 pm
Victor. I was thinking about this mtDNA and Y-chromosome problem today. Now, we are fairly sure Y-chromosome line C for example evolved in Asia, probably the Iranian plateau but I’m not prepared to place a large amout of money on that. But the mutation must have occurred in a single individual. He must have had male children but they would have only half his autosomal or nuclear DNA. His grandsons in turn would only have one quarter of his genes, his greatgrandsons one eighth, and so on. Of course they may have been breeding with close relations so there may have been many shared genes but, say, members of the C Y-chromosome line moved a small way they would have had children with women who were even more different. The genes would even more rapidly become diluted. We do know Y-chromosome C’s descendants eventually reached Australia. I think we can presume that neither the individual with the original Y-chromosome mutation, nor even his grandchildren actually took part in that movement. It would have been a slow migration across Asia, picking up resident genes as it moved. Therefore, in effect, we can say the Y-chromosome itself moved independently of the autosomal DNA or genes. Resident elements of these genes could easlily remain in spite of the expansion of Y-chromosome C. The same thing with mtDNA. But mtDNA is replaced less readily than Y-chromosome, therefore even though “the dating of genetic markers is extremely iffy and vague” mtDNA’s root is more ancient than the Y-chromosome root. The root of both is in Africa but there is no reason at all why they might go back to a single migration, led by a Moses perhaps?
A similar process has been assumed to account for many more modern Y-chromosome and mtDNA expansions but the probability it has been happening continuously throughout our evolution is usually conveniently overlooked. It seems people have an emotional need to believe we can point to a particular time and place for our origin. This need probably derives from beliefs we grow up with. We always have to fit new information with what we already believe.
I agree “As far as blond, blue-eyed, and like that, I see no reason why these have to be adaptations.” However, whenever such things have happened in any other species we have assumed they are adaptations. Why the different approach?
November 12, 2007 at 11:47 am
Well, first of all - Petraglias findings may be very interesting in and of themselves, but they do not prove that it was the same people living before and after YTT, as already pointed out. (Assuming so on the basis of what evidence Petraglia’s article cites seems terribly flawed to me. What it says is that the people that lived before and after, were on the same technological level.) The evidence doesn’t even say conclusively that they were of the same species.
The stone tool manufacturing techniques that are indentified in the findings as Middle Paleolithic, spans some 300,000 years. That is a time period / level of technology that comprise both Homo Neanderthaliensis and Homo Sapiens (and maybe other coexistent species as well). In what sense then should this be intrepreted as remnants of “modern man” (in the sense most commentators here seem to mean)?
It may well be that the pre-YTT deposits were made by later extinct individuals of Homo Neanderthaliensis and the post YTT-deposits were made by individuals of Homo Sapiens, living on a similar technological level. (Or both may be from cultures of Homo Neanderthaliensis, who were later replaced by Homo Sapiens.)
Stone age technology at this level is just to uniform in complexity to prevent an accurate identification of who deposited the material i all but some cases. Look at figure 3 in the article - it doesn’t prove what the article seem to imply (continuity)…
The technological spread indicated by functions 1 and 2 - the dimensions in the plot - show a very pronounced grouping (South African MSA). A kind of “mainstream” with variations, that completely dominates all findings.
That means that, as far as these functions may be used to differentiate between different “strands” of stone age technology, only those that occupy a position outside of the main group can be used as conclusive evidence of continuity! Why? Because when the finds are all within the mainstream, they may originate from two wholly different sources who are both also within the mainstream. So we may have two cultures - both of whom belong within the mainstream technology - leaving behind evidence that we cannot tell appart.
That would have been highly unlikely if both the pre-YTT and post-YTT deposits belonged to a smaller subgroup - and almost unthinkable if they showed some unique characteristics. (If they do, I can’t find any evidence of that in the article.)
As far as i know, much of the variation in stone tool manufacturing techniques is attributed to “physiological” reasons, such as what resources - types of stone et.c. - are available at the location, more then “cultural” reasons.
Two very different cultures in the same environment would tend to produce more or less the same tools in the same manner, because banging stones together can be done in only so many different ways…
Secondly, even if the evolutionary development that is assumed to occur during the bottleneck is a necessary cause of the later developement is not in itself a sufficient cause.
The first humans (Homo Sapiens) after the divide would still be on the same technological level as their predecessors. Therefore nearly indistinguishable from them (in these kind of material deposits). Even if the technological evolution picked up a tremendous speed later on, it was still a slow start. It would still be consistent with the findings.
Oh, and thirdly - blondness IS an adaptation; to lack of sunlight. Less pigmentation allow for more effective synthesis of vitamin D in the skin (by ultraviolet rays). In a sun-rich environment that is no problem. (But sunburn is a big problem, hence pigmentation.) But close to the arctic circle the production of vitamin D is severely hampered. (It is recomended that people of darker skin adjust their diet if they live in northern Sweden for example, for this very reason.)
Blonde hair and blue eyes are - as far as I know - two traits that have no function but can be explained anyway, since they are the result of deficient DNA. Exclude certain protein encoding alleles, and the hair and irises loose pigmentation. These traits are recessive - in any large population they would eventually disapear. But the population that adapted to the cold climate was small enough for them to “catch a ride” with other and more valuable genes.
Although cross breeding with both aliens and Neanderthals have been suggested as the source, there’s absolutely no need for so fanciful explanations…
November 12, 2007 at 5:15 pm
I’m neither a geneticist nor archaeologist, so not in a position to argue strongly with regard to either of the above posts. Terry, the point of your argument regarding Y and autosomal markers eludes me. While it’s true that the autosomal markers from any individual are going to get diluted over time, the assumption, as I understand it, is that the overall statistics for relatively static populations will remain fairly stable over time. I’m not sure what the significance of Y chromosome line C is, but if it wound up in Australia and started in or around Iran, then it could have originated via a bottleneck event somewhere in S. Asia, very possibly due to the Toba explosion, no?
What I do know something about is the musical evidence, which tells me that there is a huge stylistic gap between Africa and SE Asia and Melanesia, that could be traced to something that happened during the original OOA migration. We find an African musical signature only north and east of Toba, nowhere west of it, until we reach Africa itself, of course. We find most of the populations with an African DNA signature north and east of Toba as well. That, plus the need to explain human morphological and genetic differences, makes a strong case for a Toba bottleneck. If not that, then possibly some sort of huge Tsunami at a somewhat later time perhaps.
Australian aboriginal music is also remarkably different from anything African, suggesting that the aborigenes could have originated somewhere in S. Asia as a result of the same bottleneck. That would explain morphological similarities with certain “Australoid” tribal peoples of S. India.
Sapient — What Petraglia is saying is that the stone tools he found under the Toba ash were very similar to stone implements found in homo sapien sites in Africa. AND different from earlier types of tools employed by pre-homo sapien populations. If that turns out to be the case, then modern humans were indeed in S. Asia during the Toba explosion. He could also be wrong and the tools could have been produced by Homo Erectus or Neanderthals.
My point about “white” skin, blonde hair, etc. was that such traits could also be explained as the result of a population bottleneck in Europe that had nothing to do with adaptation. Just because a trait could have been the result of adaptation doesn’t mean it had to have been. Paleosiberians and Eskimos are not caucasian and do not have blonde hair, despite their living close to the Arctic Circle.
November 12, 2007 at 8:29 pm
Sapient: “Less pigmentation allow for more effective synthesis of vitamin D in the skin (by ultraviolet rays) … close to the arctic circle the production of vitamin D is severely hampered.
Two problems. How long ago did humans get close enough to the Arctic Circle for lack of sunlight to be a problem, and didn’t they have clothes by then? As Victor says, “Paleosiberians and Eskimos … do not have blonde hair, despite their living close to the Arctic Circle.”
So what does that do to the lack of vitamin D theory? And why is the possibility of hybrids between Neanderthals and humans of African origin part of “so fanciful explanations”. Their separation probably had much the same cause as the separation between modern Europeans and the different humans they have ran into over the last few hundred years.
November 13, 2007 at 7:11 am
Petraglia et.al. may of course be right - but I cannot see that the article proves that. I find their conclusion under-determined by the facts presented. Maybe I was a bit wordy an unfocused in my critique, so I’ll try to sum it up tighter:
We have two contradictory hypothesis:
A) Continuity between pre- and post-Toba cultures in this locale
B) A bottleneck (due to the Toba-event) cause a global repopulation/OoA
The artifacts found from before and after YTT, are more or less similar in technological level, composition, manufacture et.c. At least enough so that the findings are compatible with hypothesis A. But it is not enough to rule out competing hypothesis B.
The material finds - as I read the article - could be the result of two wholly different populations, that just happened to leave similar enough material deposits. (Because both their origins had similar enough technology - i.e. were part of the “mainstream” group in figure 3, in the article.)
Maybe I’m missing something, but I can’t find that the article presents enough data on the tool-findings that are at the same time supporting continuity between pre- and post-Toba cultures, yet distinguishes them from other possible sources.
Yes, there are some distinguishing characteristics, but I don’t think that they are strong enough to rule out the possibility of parallel origins since a great part of them may very well be the result of adapting the same general technology (shared by many cultures) to the material circumstances at hand (what I called ” ‘physiological’ reasons” in my first post). Therefore the conclusion is underdetermined.
As to the other issue, the adaptive value of pale skin, lack of blonde hair et.c. among innuites and paleosibirian populations, doesn’t constitute a counterexample to my argument.
The mutations that give rise to the differences of, on the one hand, eye and hair coloration, and on the other skin tone, are separate and independent.
There exists a marked evolutionary pressure to adapt skin coloration to the level of UV lighting. The correlation between skin coloration of indigenous populations and level of UV-light, can be described with a very neat equation.
Innuite and some closely related peoples are exceptions - who don’t have suficiently light skin to correlate to the latitude of their habitats. But the reason for that is in their diet. The vitamin D insufficiency that produces the need of adaptation in the first place, is not a risk for them since their traditional diet is very rich on vitamin D.
November 13, 2007 at 8:53 pm
Sapient wrote, “We have two contradictory hypothesis:” Surely the easiest way to decide between them is to examine extinction in the wider mammalian comunity. Were there other extinctions in India associated with the Toba eruption? If so the bottleneck looks likely, if not it’s unlikely.
As for “The vitamin D insufficiency that produces the need of adaptation in the first place, is not a risk for them since their traditional diet is very rich on vitamin D.” So why do they have an eyefold, greatly reduced facial hair and extra keratin in their skin? Presumably nothing to do with the environment they evolved in?
November 14, 2007 at 9:19 am
TerryT wrote: “So why do they have an eyefold, greatly reduced facial hair and extra keratin in their skin? Presumably nothing to do with the environment they evolved in?”
Yes, precisely that. But not the environment they live in NOW, they were pre-existent. The arctic environment don’t select for these traits. (As far as we know, anyway. And we probably would.) But neither are they a problem - there’s no evolutionary “encumberance” in carrying these traits so they stay in their genome.
About comparison to animal taxa before and after the Toba-event. Yes, that could be one way. Maybe someone will try it (either trying to draw conclusions from what data may already exist or by making new examinations).
But it may not prove anything. There’s no way to know what kind of animal fossils there “should be”. And even if we don’t find what we expect, that doesn’t necessarily prove that animals of that kind didn’t live in the indian subcontinent anyhow. Maybe they didn’t but without leaving any fossil remains… Or, if they left remains, we might not find it because we look in the wrong place.
That’s the problem with archaeology. Absence of evidence, isn’t evidence of absence.
November 14, 2007 at 6:19 pm
Sapient wrote: “Absence of evidence, isn’t evidence of absence.” I’ve only ever heard that argument from creationists and IDers. Am I correct in my conclusion in this case?
November 15, 2007 at 5:40 am
As I see it, an 8 foot thick layer of volcanic ash is all the evidence anyone should need of the devastating effects of the Toba eruption. It may not have been so devastating as to cause major extinctions, but it would certainly have produced genetic bottlenecks. The real mystery is not whether a bottleneck could have been produced, but whether or not modern humans were in the area at the time. If Petraglia’s analysis of the stone artefacts is correct, they were. And if they were, it’s hard to see how they could not have been profoundly affected by the Toba eruption.
November 15, 2007 at 6:56 am
TerryT wrote: “I’ve only ever heard that argument from creationists and IDers. Am I correct in my conclusion in this case?”
You could not be further from the truth. I am as far as possible from a creationist point of view.
The maxim - although sometimes abused by religious appologists - is one of the fundamental laws of scientific reasoning.
But it IS possible to abuse it, of course. In this “catchy” wording, it is not very elaborate - it avoids one crucial thing that I find many creationists are ignorant about (or just don’t care about); the issue of positive or negative hypotheses.
There are times when abscense of evidence IS evidence in itself. If you say “there is a coin in my pocket” and we investigate that without finding any evidence to support your claim, that disproves it. But only as long as our investigation would reasonably find evidence if there was a coin in your pocket.
If, on the other hand, I say “you don’t own any coins!” I cannot prove that by saying “Look, I’ve checked your pants and there were no coins in the pockets” because you may own coins without keeping them in your pockets.
The difference between the hypoteses demands radically different methods of proof.
To make a very streched analogy to Petraglias article - he reports having found two coins, but that doesn’t prove that they were owned by the same person.
November 15, 2007 at 6:21 pm
Sorry for the insult Sapient. As soon as I posted it I looked back at your comments and realised I was totally wrong. Again, humblest apologies.
Some time back Victor wrote: “the point of your argument regarding Y and autosomal markers eludes me”. The point I was making is that we can’t assume the presence of a particular Y-chromosome or mtDNA line says too much about population migrations. A single gene can move through a population without being intimately associated with a suite of genes.
November 25, 2007 at 12:12 pm
According to Sapient:
“We have two contradictory hypothesis:
A) Continuity between pre- and post-Toba cultures in this locale
B) A bottleneck (due to the Toba-event) cause a global repopulation/OoA”
I don’t see A and B as contradictory. A bottleneck is consistent with continuity, not extinction. If the tools found under and over the Toba ash were products of the same culture, as Petraglia claims, that does not mean no bottleneck occurred — even if there were only a few survivors in that locale, they would still have been making and using the same type of tools. Considering the 8 foot thick layer of ash it’s hard to understand how there could not have been a bottleneck.
TerryT:
“Sapient wrote, “We have two contradictory hypothesis:” Surely the easiest way to decide between them is to examine extinction in the wider mammalian comunity. Were there other extinctions in India associated with the Toba eruption? If so the bottleneck looks likely, if not it’s unlikely.”
According to a recent paper, “Big Cat Genomics” (http://home.ncifcrf.gov/ccr/lgd/staffInfo/staff/pdf/johnson_annReviewHumanGenetics2005_big_cat_genomics.pdf), there could have been at least one:
“Tiger genetic diversity dates back to only 72,000–108,000 years ago, when a founder effect established an ancestry for all modern tigers (Table 2). The dates correspond roughly with the catastrophic eruption of the Toba volcano in Sumatra about 72,500 years ago (82).” (p. 418)
November 29, 2007 at 11:50 am
The Toba event made people wonder and the wandering ended up on the moon. This … until they found out that they were from Africa themselves.
November 29, 2007 at 7:11 pm
Victor, thanks for that. I’ve only just noticed your reply. The link doesn’t come through here but I’ll google it.
November 29, 2007 at 7:13 pm
No. Doesn’t work. If you find it again could you please let me know?
November 29, 2007 at 8:39 pm
I’m not sure what the problem is, but here it is again:
http://home.ncifcrf.gov/ccr/lgd/staffInfo/staff/pdf/johnson_annReviewHumanGenetics2005_big_cat_genomics.pdf
It’s a long pdf file so takes a while to download.
November 30, 2007 at 12:16 am
Very interesting Victor. Thanks. I notice that Asian leopards didn’t suffer a bottleneck at that time, which is surprising, although the authors mention Asian elephants did.
November 30, 2007 at 7:29 am
Terry, it would be important to know where in Asia each of these species was centered at the time of the Toba blast. It would have affected those west of Toba but not anywhere else, as the prevailing winds were apparently toward the west — or northwest. Note that many indigenous peoples now living east and southeast of Toba tend to have African morphology and genetics and also share certain important cultural traits with Africa (including what I call the “African signature” in their music) while those living to the west, including the Indian “tribals” apparently do not.
December 23, 2007 at 4:05 am
Sapient -
I simply had to let you know that I very much enjoyed reading over your extremely reasonable and completely logical arguements. You solidly clarified in so many words on a simple blog things that I have been desperately trying to explain to one of my extremely knowledgeable but damn stubborn professors for the most of my semester thus far! Even while that Terry T. fellow was trying to pick a fight you very confidently and indubitably provided explanations and the like. You sound like a seasoned debater to be honest!
I myself am technically a Christian creationist (not all Creationists’ ideas go along with the scriptures in a literal sense) and a very religious one at that. I appreciate the value of symbolism in the scriptures that most religious persons do not. I do not quite understand how or why suggesting that an individual is a creationist would be considered an insult (frankly I can only assume that an individual would only qualify such an idea as an insult out of complete ignorance and bias). Nonetheless, the assertion that you yourself were a creationist made me laugh. Once again, I wholly appreciate your obvious insight on the studies of the paleoanthropological world… even the ideas - though they may be few - presented in your response to this article. By the by, sorry if this sounds like a nonsensical ranting compliment - it’s almost 5am over here and I haven’t gotten any sleep!
December 25, 2007 at 1:41 am
Rebbecca K wrote, “that Terry T. fellow was trying to pick a fight”. Not really. I was merely drawing attention to the fact that the difference between humans pre- and post- Toba may not have been that great. There is actually nothing we can use to categorically distinguish “modern” humans from “ancient” humans. That brings up the question of when were humans “created”?
January 7, 2008 at 4:44 pm
It is pretty difficult to refute the “out of Africa” hypothesis when you look at the physical evidence. Humans were running sophisticated mining operations in the Lebombo Mountains of South Africa 100,000 to 80,000 year ago. These mines include tunnels worked by thousands of miners who dug tons or red ochre. The oldest known counting device was also found in these mountains: the Lebombo Bone, which represents a binary calendar. The Toba eruption, while later, does not seem to have effected populations in Africa directly, but it doubtless did contribute to teh global climate changes that would led to the Guirian Wet Period (likely the time of Noah’s flood). For more on this see: http://jandyongenesis.blogspot.com/2007/10/africa-in-days-of-noah.html
January 7, 2008 at 9:10 pm
So Noah’s flood has now shifted to Chad? I thought it was in the Black Sea. Or in Mesopotamia. I suppose that’s the advantage of myth, it’s very flexible. Noah’s flood can be anytime you choose.
And the Toba eruption was long before what your link claims as a date for the Gurian Wet period.
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