Prometheus Unfounded: Contradictions and Conundrums at Wonderwerk Cave

Wonderwerk Cave profile (Photo by M. Chazan)

I’ve previously opined on aspects of the claim for very early fire use at Wonderwerk Cave, South Africa here, here, here, and here. In brief, it’s Swiss cheese. Today I’m beginning to look at Peter Beaumont’s 2011 synthesis of the ‘evidence’ for hearths in the cave, published in Current Anthropology. Forgive me if this comes across as unusually pedantic–I find the author’s descriptions to be less-than rigorously scientific, and thus less-than helpful if one’s hoping to cast a critical eye on what amounts to his life’s work. I’ve found it all very difficult to wrap my brain around. See what you think.   
     Beaumont begins his discussion of what he calls ‘hearths’ by mentioning that in places he observed ‘poorly defined ash lenses’ and in other places ‘ash-rich’ deposits, which he thought had been ‘single hearths … largely destroyed (perhaps by trampling).’ It’s unfortunate that there could be so much ambiguity entailed in such a short paragraph.
     First of all, what really is the difference between a ‘poorly defined lens’ and an ‘ash-rich deposit’? Aren’t they both ‘ash rich’ if you can recognize the ash in profile? And what about the other sequelae of burning, charcoal and the reddened substrate. I would have expected any fire that could turn plant fuel to ash would have been sufficiently hot and of such a duration that it would also have reddened the sediments beneath the fire. Moreover, in many cases where reddened sediments and ash are visible in a stratigraphic sequence there is a higher than average chance that there will be a layer of charcoal-enriched or blackened sediment between the reddened substrate and the ash. Trampled or not, Beaumont’s inference that these ash lenses were hearths is hardly to be believed on the face of it.
     Presumably Beaumont wants us to believe that, in the case of the ‘ash-rich’ places, any vertical distinction that at one time would have been evident between the ash and the reddened sediments had been obliterated by treadage. Yet, if that were the case, how is it that he’s able to discern anything that might be called discrete (albeit poorly defined) ash lenses? For Beaumont to be able to observe ‘lenses’ comprising ash, those lenses must have escaped, in large part, the destructive results of trampling. And surely, if the ash ‘lenses’ had escaped the ravages of time and trampling such that they were visible in profile, the underlying reddened sediments would also have retained enough integrity to be visible, too! Yet, the author mentions nothing about the substrate, reddened or otherwise. Odd. On the other hand, one has to agree that in all likelihood it was trampling that transformed what had once been intact ash deposits elsewhere in the cave into something the author calls (merely) ‘ash-rich.’

[My recognizing problems with Beaumont’s after-the-fact verbal descriptions doesn’t ensure that the his inferences are incorrect. However, one does have to wonder. Doesn’t one? One would have thought that a perspicacious referee or editor would have noticed these vague and incongruous descriptions. Wouldn’t one?] 

     Alas, the abovementioned ‘hearths’ aren’t the only curiosities to be found in Beaumont’s treatment of putative fire use at 1+ Ma. In another example he describes stratum MU2, in excavation 5, where as much as 45 cm (!) of the stratigraphic column ‘is very largely composed of white ash with many burned bones and fire-damaged Middle Stone Age artifacts.’ This ash apparently ‘accumulated slowly’ and continuously between about 1,155,000 and about 70,000 years ago. [Get out your calculators!] 
     Depending on what Beaumont means by ‘very largely composed of’ [and it’s not at all clear], it sounds as if he’s suggesting that for 1,085,000 years a very wide area of the cave received little other sedimentary input than that of completely combusted plant material. That’s a prodigiously long time for a single depositional process to have endured, and a phenomenally long time for a large surface comprising a substance as mobile as ash to have survived without either blowing away or being adulterated by larger [especially inorganic], autochthonous clastic input. 
     Even more mysterious: Beaumont claims that the ash was the result of thousands of fires fueled by above 15 tons of fuel. It’s really hard for me to imagine that such a focus of hominid activity could have escaped the inevitable, and destructive, treadage that would have accompanied that use of that part of the cave for what amounts to a single activity–that of making and keeping fire–over such a vast expanse of time. I suppose it’s not impossible. But, probable? I really don’t think so. Plausible? Barely.
     Beaumont’s description of MU 2 in excavation 5 just makes no sense. If his account of its clastic composition is accurate, nothing but a long-lived colony of fire-loving faeries could have produced it! There must be alternative explanations. And, indeed there are, provided by an unlikely source–the latter-day excavators of Wonderwerk Cave, the very ones who have recently reprised Beaumont’s long-standing claim of fire use by Acheulean hominids.
     Here’s what Matmon, Chazan, Porat and Horwitz conclude in ‘Reconstructing the history of sediment deposition in caves: A case study from Wonderwerk Cave, South Africa‘ published in the Geological Society of America Bulletin (First published online October 14, 2011, doi: 10.1130/​B30410.1).

The cave sediments comprise a sequence of fine sands and silts that were transported naturally by wind to the environs of the cave and later into the cave by water. Transport within the cave occurred by low-energy water sheetflow, which distributed and deposited the sediment in its final location. Field observations and grain-size distribution analysis of the sediments inside and outside of the cave imply the following sediment transport scenario: eolian transport of Kalahari sand to the Kuruman Hills, slope wash of the eolian sediment into the intermontane valleys, fluvial transport of the sediment from the intermontane valleys to the entrance of the cave, and final deposition of the sediment inside the cave by low-energy water action.

 These are the verbatim conclusions. Unfortunately for the authors, this sequence of transport processes leading to the input of allochthonous sands and silts at Wonderwerk Cave can equally explain the presence of anything that would be as easily transported as sands and silts. Indeed, anything lighter than fine sand–if it shows up at the doorstep–would have been subsequently transported into the cave by sheetwash. Sheesh! They’ve done my work for me! 
     Their conclusions also solve a riddle that I found while wandering through the images from Wonderwerk. This one shows non-conformable and curiously wavy strata. I’ve drawn yellow rectangles where I see evidence of what appear to be erosional events overlain by non-conformable strata. These observations support the conclusions of Matmon et al. It appears that there have been numerous erosional episodes during the build-up of sediments in Wonderwerk Cave. The wavy contacts suggest an agent even more energetic than sheetwash. If these observations are borne out it’s clear that at times the input of material and liquid from outside the cave was considerable.     

After Berna et al. 2011

Make of it what you will. 
     Beaumont describes ‘grass mats’ in various stages of combustion that occur here and there in the cave. Regardless of how they arrived at the cave’s doorstep, in they went–wind-whipped dry grass, partly combusted grass, grass ash [try saying that five times really fast without saying something unfit for polite company], small bits of burned bone made as light as fine sand by partial combustion. You name it! Matmon et al.’s conclusion opens the door to serious questioning of Wonderwerk’s depositional history. How can they claim, unequivocally, that any wind-transportable allochthonous sediments came to rest in the cave by the hands of hominids?
     Seriously! They are way past the bounds of logical inference when they claim that any of the tiny particles that Berna et al. describe in exquisite micromorphological detail were left there as a result of hominid behaviour. Somebody’s gotta tell them. I’m trying me best. But they appear not to be listening.
     So, get out there to the meetings and to your classrooms and call out the litany of overwrought inferences of hominid behaviour that keep emanating from Wonderwerk Cave!     

One thing’s for sure: the excavations at Wonderwerk Cave are looking more and more like job security for this Subversive Archaeologist.

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Are There Bats In Beaumont’s Belfry? Once More Down the Wonderwerk Cave Rabbit Hole.

Okay! Ready for another visit down the Wonderwerk Cave rabbit hole? Keep in mind the main points of Berna et al.’s paper claiming million-year-old fire use at Wonderwerk. First, lots of burnt stuff–animal bone, grass, ash. Second, no bat guano ’cause there wasn’t any Berlinite in the deposits [long story, that]. Their conclusion: no spontaneous combustion. That leaves Homo erectus [or a reasonable facsimile] as the only actor that could have been responsible for the fires in the cave. And Berna et al. report that the senior archaeologist, Beaumont, ‘reported macroscopic evidence for burning.’ 
     I had to see what he had to say. So I’ve collected the pertinent portions of 

‘The Edge: More on Fire-Making by about 1.7 Million Years Ago at Wonderwerk Cave in South Africa,’ by Peter B. Beaumont (Current Anthropology52585-595, 2011). 

I call Wonderwerk Cave a rabbit hole mostly because the logic of what’s been claimed can be a little hard to follow [to say nothing of ‘swallow’]. 

     One of the first bits we learn is that
the cave was exploited for “agricultural fertilizer” between 1940 and 1944, when the cave interior was largely dug out to a depth of up to 2.5 m     
Here’s a link to the full-sized version on my Flickr account. 
A back-of-a-napkin estimate of the volume of cave earth removed by the ‘diggers’ yields a figure of 375 cubic metres. I know that most of you know what a cubic metre is, since most of you have had the experience of digging a 1 by 1 to a depth of a metre. But, really, how much Wonderwerk dirt was bagged for fertilizer? 
     A 40 lb (~22 kg) bag of fertilizer works out to about 40 litres. A cubic metre contains 1000 litres (doh!). So, those 375 cubic metres removed from Wonderwerk would have yielded about 9,375 bags of fertilizer. That’s a lot of dirt! That’s a lot of labour, too. Yet, as you’ll discover a little further down, Beaumont surmises that there can’t have been much in the way of effective fertilizer in the dirt the diggers removed. Keep that in mind as we work through the rest of Beaumont’s ‘observations’ on Wonderwerk Cave.
     Next Beaumont muses on the likelihood that there was ever a significant number of bats ‘hanging’ around in the cave. He turns first to a modern observation     

Zoological studies at regional bat caves show that all have dark interiors, little or no air movement, and relatively high humidity levels; the only place in Wonderwerk that partly matches those conditions is a deep roof cavity at its rear, where a small number of bats were seen in 1988, briefly replacing the barn owls that usually reside there…

My guess is that we’re to assume nothing has changed during the time that the upper 2.5 metres of the stratigraphic column had built up–i.e. that dirt removed for the presumed phosphate-depauperate fertilizer. I find this to be an astonishing assertion. But, there’s more. 

As for bat dung/guano, this was originally linked to the red sand strata …, a claim not supported by a study of the sediments …, which showed that all levels are mainly (>90%) made up of sand and roof fragments, or by the finding that the microfauna indicates a preponderant avian occupation of the cave by barn owls…, with only modest amounts of bat guano likely confined to lenses below the roof cavity near the back wall.

Here the author tips his hand. Of course! There never were bats in the cave in any number! The presence of rodent remains convinces him that the major avian residents had been barn owls–for a million bloody years! 
     This strikes me as an odd conclusion to make for three reasons. First, the rodent remains wouldn’t have been in the cave had it not been for the owls. But that’s not germane to this question, since bats don’t eat small furry creatures and therefore would have left nothing other than dead bats, which are in evidence in the cave sediments.   

     Second, does he think that bat guano fossilizes? Well, if he does, he’s very wrong. It decomposes like any excrement, leaving phosphate minerals. Thus, if at present it’s invisible in the cave sediments we should expect nothing less. And until Berna et al. publish the complete list of phosphate minerals they did find in the cave, we’re left in the dark as to the likelihood that bats ever left much behind in the cave [that wasn’t mined by ‘diggers’ that is].  
     Lastly, it’s laughable when the author asserts that bat guano would have accumulated only where bats have been observed to roost in the cave in the past hundred years. We’re talking about a MILLION years, fer gawd’ sake! Beaumont must be the most extreme proponent of uniformitarianism that ever set foot in a palaeontological locality! 

     His conclusion, which appears below, is a case of special pleading, if ever I heard one.

From these data it is evident that the 1940–1944 diggers were marketing a product that contained little in the way of fertilizer

If so, they must have been running a con. And, if it was a con, this might be the only time in criminal history that such a gambit involved hard labour on the part of the grifter! Hey. Maybe not! Maybe the cons were so good at their game that they did a Tom Sawyer on some unsuspecting yokels, and had them dig out half the cave! 

Please, make your own conclusions. I’m happy to hear your reasons why anyone should accept Beaumont’s assertions at face value.  


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