Stay-At-Home Modern Humans Stranded in South Africa for 50,000 Years. What’s Up With That?

Pinnacle Point Caves (PPC) in relation to Klasies River Mouth (KRM)  cave and Blombos Cave (BBC), three of the best known southern African localities with modern human accoutrements as early as 70 ka to 100+ ka. 

In the midst of the recent science-media frenzy about bows and arrows at Pinnacle Point, I thought I’d best expand on my reasons for doubting, en masse, the 70 ka to 90 ka [and beyond] dates for what appear to be unequivocally modern behaviours in a growing number of southern African archaeological sites. I’ve been working on this for several days, and the more I look, the more I see evidence of a real problem with optically stimulated luminescence (OSL), the technique used at all of these sites to estimate the age of the deposits. As I’ve mentioned previously [e.g. here], the primary assumption underpinning OSL age estimates is this: each individual quartz grain removed from the archaeological deposits MUST have been exposed to sunlight for long enough to have released any free electrons trapped in its crystal lattice. Given that all of these early dates derive from cave deposits, the primary issue for the OSL specialist is eliminating any quartz grains that have not been exposed in the manner just described. It’s one thing to recognize this pesky problem; it’s quite another to overcome it. And that, I think, is where OSL falls down. Whether or not a given age estimate is accurate becomes a real guessing game, as we’ll see in a moment.  

Three representations of the stratification at Pinnacle Point PP5-6. Source: Brown et al. 2012

As you can see above, in the recently published profile from Pinnacle Point site PP5-6, the OSL picture is evidently not straightforward. The date of 53 ka highest up in the profile is superposed on a date of 60 ka. That is consistent with the stratigraphic relationship between the sediments that yielded the dates. However, the next lowest in the column is, again, 53 ka. Then come 56 ka, 52 ka, 50 ka, followed by 52 ka, 60 ka, 65 ka, 65 ka, 69 ka, then 66 ka, 66 ka, 64 ka, 72 ka, 71 ka,74 ka, 69 ka, 77 ka, 73 ka, 71 ka, 69 ka, 69 ka, and lastly 78 ka. Clearly this is not an ‘internally consistent’ temporal sequence. These age estimates are roughly sorted youngest to oldest, but given the lack of coherence, how is one to assess, much less find acceptable, either the youngest or the oldest dates?
     For example, does one conclude that the real age of this stratigraphic column ranges from 53 ka to 78 ka? How about 53 ka to 69 ka? Or 60 ka to 69 ka? Moreover, with such variance from what one should expect of the age succession in a sedimentary column that has maintained temporal integrity, how do we know that any of these estimates are accurate? All this points to, in my barely savvy opinion, serious difficulty with the technique, most likely due to the intractable problem inherent in the primary assumption of the technique. And, if the very latest results of the best of the best practitioners yields such shaky outcomes, what does it say about all of the other South African site chronologies? Here, then, lies the very real possibility that the OSL technique is single-handedly creating a false picture of modern human origins throughout the southern region.

Stratigraphic profile of La Quina, the type site of the Quina Mousterian. All of the objects illustrated are éboulis, clasts of all sizes and shapes, which have spalled off the bedrock and been incorporated along with the archaeological materials.

     In this I’m reminded of what’s now a discredited relative dating technique that European archaeologists depended on for a good long time. I refer to the technique of éboulis analysis that underpinned [especially] the French Palaeolithic chronology for much of the late twentieth century. Briefly, the analyst qualitatively assessed the angularity of small pieces of bedrock breakdown and assigned an age estimate that coincided with what was then considered to be a four-stage European glacial cycle–Gunz, Mindel, Riss, Würm. The most angular pieces represented cold or dry or both, and the most rounded pieces warm and wet or both. It seems a bit naïve by today’s standards. However, it was gospel for decades. One day it all came crashing down. After that, everyone picked up the pieces and moved on. Thus far archaeologists of the Middle Pleistocene haven’t resorted to OSL for dating. However, they do use thermoluminescence, which depends not on individual quartz grains, but rather on pieces of flint that have been subjected to high heat. There’s certainly less doubt about whether or not a piece of flint has been heated than that a tiny grain of quartz was ever exposed to sunlight. 
     In making this comparison between éboulis analysis and the OSL dates from southern Africa, I don’t mean to suggest that the two techniques are equal. Rather, I make the comparison because, in the past, an error-prone technique was used to provide the chronological framework for an entire sub-continent. That’s the direct comparison to be made. The southern African cave sites are universally dated using OSL or other equally shaky [to my mind] techniques.

The crux of the southern African OSL dates. In relation to the earliest evidence of modern human behaviour everywhere outside of Africa, and the speed at which Eurasia was ‘colonized’, the southern African dates stand out like a sore thumb. 

     Having made the comparison between éboulis and OSL, I can now introduce what I believe to be several data sets suggesting that the southern African cave age estimates are anomalous when compared to the rest of the world. For, when it comes to the early dates for modern human behaviour in southern Africa there is an absence of parsimony. Parsimony, if you’ll recall, is the central point of Occam’s Razor, the idea that, when deciding which competing hypothesis is the more correct, the one that makes the fewest assumptions should be selected. Occam’s Razor is by no means a law of nature. It merely crystalizes what empirical scientists have know for some time–the more auxiliary hypotheses you need to support your main conclusion, the less likely it is to be the right one. In the case of the early dates for modern human behaviour in South Africa, there is much that flies in the face of Occam’s Razor.
     Take, for example, the overwhelming evidence for the almost instantaneous spread of behaviorally modern humans to the furthest reaches of Asia, which happened about 45 ka. Australia was colonized at this time. So were some of the the furthest reaches of Europe–England, for example, at 44 ka. The best explanation for the absence of modern human archaeological assemblages prior to this time is that there simply were no modern humans outside of Africa prior to that time. The question thus becomes, if humans could expand the length and breadth of Asia in an eye-blink of geological time, why didn’t it happen earlier, when modern human behaviour is claimed to have had its start 70 ka to 90 ka ago in southern Africa?
     To explain the apparent lag between the emergence of modern human behaviour in southern Africa and that which inhered everywhere else in the world post 45 ka, the various archaeological teams must invoke untested, and indeed untestable hypotheses as to the reason for those moderns staying put for anywhere between 164 ka and [taking the youngest date from PP5-6] 53 ka. One hypothesis has that population bottlenecks occurred due to environmental circumstances [as yet unrecorded], after which cultural achievements of the modern populations were stultified, only to reappear some 30,000 years later, at which time the archaeology records the rapid spread of modern humans throughout what’s been called the Old World.
     In July of this year we saw a report from Border Cave of a modern human archaeological assemblage that dates to about 44 ka, a result in accord with the beginning of modern human behaviour in Eurasia. But, because they found no earlier deposits, the authors find it necessary to replay the tape of the ‘early’ teams, that the Border Cave moderns must represent the hypothesized re-fluorescence of modern humans preparatory to world domination. Once again. I think such intellectual reaching is unnecessary, at best, and obfuscatory at worst. I do not mean to suggest that the obfuscation is deliberate. The archaeologists who rely on OSL age estimates have nothing else to go on. Or, at least, they have no reason to think that their information is in error. After all, the best of the best are working at Pinnacle Point. Who could doubt their veracity? Who would, much less?

Modern human artifacts from Border Cave at 44 ka. Touted to be the earliest evidence for the same culture that existed ethnographically in the vicinity of Border Cave. [Take that with an anthropological grain of sand.] Source: D’Errico et al. 2012.

     I know. I know! We’re dealing with Culture. And culture theory says that the early moderns in southern Africa might just have decided that they wanted to stay put and not colonize the known universe. If you think about it, how would they have known they were choosing not to colonize the rest of the world, unless they knew there was a ‘rest of the world’ to colonize. And, if they did know that there was a ‘rest of the world,’ why is there no evidence for those modern humans until about 45 ka everywhere but southern Africa. If, and I have no doubt, the early moderns in South Africa were anything like modern moderns, or a great many ethnographic moderns, they couldn’t have resisted seeing what was beyond the next ridge. Yet it would seem that they ‘chose’ to stay put, enjoying the fruits of their modernity all by themselves, thus endangering their persistence by allowing themselves to be buffeted by the whims of the environment. That doesn’t sound like modern me to me. [N.B.: I’m only being half facetious.]
     I supposes one could suggest that there were natural barriers to their spread out of southern Africa. But, there are no natural barriers to movement in coastal Africa, nor would there have been when the sea levels were depressed during the glacial stages of the Pleistocene. If they could process pigments and decorate ochre, make beads, and arrows, they were equally capable of making boats to cross the broad reaches of Africa’s rivers where they meet the sea. After all, the colonizers of Australia crossed at least 90 km of open ocean at around 45 ka. Surely the precocious moderns in south Africa at 70 ka to 90 ka could have done the same. So, the big question is why did they stay put in southern Africa? Huh? Riddle me that, Batman. Apparently the Wall Street Journal has a suggestion.

     So, you see, reason alone tells me that there’s much wrong about the early dates from southern Africa. And my instinct tells me that the OSL dates must be wrong. As I’ve said to you before, will some kindly physicist not come forward to examine the mathematical filmflammery that accompanies OSL age estimates, and thereby save me from this empirical purgatory??? The flimflammery in question.

Please??? I’m beggin’ ya.


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The ‘MSA’ and Modern Humans: It’s Only a Matter of Time

What counts is not what sounds plausible, not what we would like to believe, not what one or two witnesses claim, but only what is supported by hard evidence rigorously and skeptically examined. Extraordinary claims require extraordinary evidence.   Carl Sagan 

BBC: Blombos Cave PPC: Pinnacle Point Caves KRM: Klasies River Mouth Cave

The southern African publishing machinery is in high gear when it comes to the so-called Middle Stone Age (MSA). It feels like there’s a new claim every week. In this case, similar claims’ve been made before. But this time it’s for … are you ready for this? It’s a big surprise, I know. But this example is…wait for it…Yes! The oldest piece of worked ochre ever reported! A-bloody-mazing! Those MSA people were modern humans for sure! And they were damned good at it, too, if I’m any judge! More on the ochre after I tell you why I’m telling you this.

     All the evidence points to these discoveries being the work of people like us–the skeletal remains from Klasies River Mouth at 75 to 125 kya (modern human, chins and all!), the Howieson’s Poort stone artifacts at Bombos Cave and elsewhere from about 65 to about 60 kya (to all intents and purposes like the Mesolithic of Europe with its backed blades), the beads, the ochre, pigment grinding tools, and more. 
     The MSA of southern Africa is nothing like the Middle Palaeolithic of most other regions. Quite simply, while the Neanderthals and skeletally modern humans in Europe, southwestern Asia and northern Africa were still hacking flakes off ‘Mousterian’ bifacial cores [or handaxes, if you prefer], sometimes taking smaller flakes off the edges to keep them sharp, and trying to rejuvenated their bifacial cores with a prepared platform and a might whack intended to split the core in two (often only resulting in the removal of just a final flake–a ‘Levallois’ flake [if you prefer]), the MSA people of SA were acting just like you and I would have (minus all of the industrial culture accoutrements like white wine [most likely] and Saturday morning cartoons on TV).

Howieson’s Poort lithics (Image credit)

    What to make of all this really early ‘industry?’ It’s not a trivial point. As far as the archaeological record of the rest of the world goes, these people, at 100 ka and more, were upwards of 60 ka ahead of the cultural curve of the rest of the world. So it’s an untrivial, and still open, question what kept people like us from doing, in the first 60 ka of modern human history, what members of the same species evidently did in an instant of geological time once we stepped outside of Africa. Let’s face it, after about 40 to 50 ka ago it was like modern humans were shot out of a cannon. Australia was reached in the blink of a geological eye. Europe? Same story. Eastern Asia? The same. And during an ice age, no less. Eat your hearts out, Homo erectus! Homo sapiens rules!

     As you might imagine, I’m troubled by all this precocious behaviour on the part of antipodean Late Pleistocene southern Africans. It’s a conundrum that I can’t get out of my head. And every time a new claim comes down the ‘pike I get more irked by my inability to explain it, or even to conjure up a plausible scenario. Believe me, this enigma is nothing like the other stuff that irks me [of which you’re all aware by now]. This is us–unequivocally modern–but it’s us when we shouldn’t be there. I know. I know. That’s not scientific, Rob. You should have an open mind. [That’s all well and good, but an open mind isn’t the same thing as an empty one–I need an answer, not a reminder of my shortcomings!]
     I’m confused, too, about use of the term Middle Stone Age for what is obviously the work of both skeletally and behaviorally (and cognitively) modern humans. Someone in the know might be able to help me here [if I could get the bleeping comments to work again!]. Is it called MSA because it’s older than a certain arbitrary cut-off on the geological time scale? Why don’t they just call it ‘Earliest Upper Palaeolithic’ or something like that? Somebody please explain!
     All of this very early modern human evidence from southern Africa reminds me a bit of the myriad claims for Pre-Clovis occupation of the Americas that have been erected, assailed, and finally collapsed under the weight of skepticism that usually accompanies such assertions. The artifacts are real. The dirt’s real. But something’s always wrong with the dates [except, perhaps, Calico Hills, where the eye of the beholder was just too clouded by its infatuation with broken rocks to see the forest for the trees]. That’s the way it always ends, with a dying fall. The claims, one after another, are justifiably questioned. No resolution. But the claims fall by the wayside, and no one makes an effort to get them back in the mainstream. It’s happened over and over and over again. My strong suspicion is that it’s happening in South Africa, but without the questions, without the doubt. And that, alone, worries me, and suggests that there’s a systemic problem.
     I have a fearless prediction. One day either the late dates for everything outside of Africa are going to be shown to be too young, or the inverse will prove to be the case. I think you know where my money is.
     One final thought. For years it’s been the orthodoxy to think of the human lineage as having been on a slow march from ape-dom to humanity. You’ve heard it. Sure you have. For ‘99% of human history we were egalitarian hunter-gatherers.’ [Stan: I remember you saying that in Old World back in ’86–no shame implied. It has been the mantra for decades.] Then agriculture happened and we all went to Hell in a hand-basket and we ended up (some of us) Capitalists, and look where that’s gotten us! [Ruth: I’ve always had a bone to pick with that one!]
     What if we weren’t human until recently? In a way I think it lets us off the hook. After all, the first stone artifacts are 2.5 MILLION years old. If we’ve been thinking like we do now for 2.5 million years, I’d say we probably don’t deserve to survive as a species, given the mess we seem to have made of things in just a few tens of thousands of years. BUT, if we only became human give or take 40,000 years ago, and if the first 30 of those were spent coping with an ice age, that means we’ve only had about 10,000 years to figure things out. I like that better. Because I think we’re better than the long chronology paints us. I like to think that we’ve come a LONG way in 10 ka.   
     Think of it. Domestication at give or take 10. Cities and monumental architecture, art, writing, by, say, 8 or so. Philosophy, drama, mathematics, geometry, science, by 4 or so. I mean, if you look at it from the short chronology point of view, we look a lot better. I’d hate to think that we’d been at this whole human thing for 100,000 years.
     We’d seem REALLY pathetic.

Back to the ochre that persuaded me to write the above. With all due respect to Francesco d’Errico, Renata García Moreno, and Riaan F. Rifkin, authors of ‘Technological, elemental and colorimetric analysis of an engraved ochre fragment from the Middle Stone Age levels of Klasies River Cave 1, South Africa‘ (Journal of Archaeological Science, 39, 942–952, 2012), I fail to see why this publication is so effing important. Imagine someone in Europe publishing this: ‘Ooh, ooh, another piece of ochre from the Upper Palaeolithic of France!’ They’d be laughed out of the academy–even if it were the oldest such artifact ever found. So, forgive me if I’m less than fired up about this amazingly complex and scholarly article about a lump of iron oxide with a bunch of scratches on it. Mind you, if the scratches spelled out the first five verses of Genesis, there might be a story there. Otherwise…yawn.

From d’Errico, Moreno and Rifkin 2012

I hope this, my attempt to explain more of my mystification with the MSA of southern Africa, hasn’t kept any of you from your naps!
     Be well. Have a good weekend. Thanks for dropping by.