The Raw and the Cooked: Apologies to Claude Lévi-Strauss

As you might imagine, I've been wrestling in silence with Richard Wrangham's cooking hypothesis for some time now. This is what Publishers Weekly had to say about Catching Fire, RW's popular book on the subject.

Contrary to the dogmas of raw-foods enthusiasts, cooked cuisine was central to the biological and social evolution of humanity, argues this fascinating study. Harvard biological anthropologist Wrangham (Demonic Males) dates the breakthrough in human evolution to a moment 1.8 million years ago, when, he conjectures, our forebears tamed fire and began cooking. Starting with Homo erectus—who should perhaps be renamed Homo gastronomicus—these innovations drove anatomical and physiological changes that make us adapted to eating cooked food the way cows are adapted to eating grass. By making food more digestible and easier to extract energy from, Wrangham reasons, cooking enabled hominids' jaws, teeth and guts to shrink, freeing up calories to fuel their expanding brains. It also gave rise to pair bonding and table manners, and liberated mankind from the drudgery of chewing (while chaining womankind to the stove). Wrangham's lucid, accessible treatise ranges across nutritional science, paleontology and studies of ape behavior and hunter-gatherer societies; the result is a tour de force of natural history and a profound analysis of cooking's role in daily life. More than that, Wrangham offers a provocative take on evolution—suggesting that, rather than humans creating civilized technology, civilized technology created us. Copyright © Reed Business Information, a division of Reed Elsevier Inc. All rights reserved.

Ringing praise, I'd say. I could spend weeks going after the plethora of assumptions that the author incorporates in the thesis from a post-modern anthropological point of view. Suffice it to say that I have issues with it.
     But that's not why I've called you here today. Lately, I came across another contribution to the literature on cooked food and primate brains. The only advice I could have given the authors while they were still writing is: 'Look before you leap.' Karina Fonseca-Azevedo and Suzana Herculano-Houzel, ‘Metabolic constraint imposes tradeoff between body size and number of brain neurons in human evolution.’ PNAS 109:18571-18576, 2012 (published ahead of print October 22, 2012, doi:10.1073/pnas.1206390109)* wrests a far-reaching hypothesis from some interesting brain- and body-size data on a range of primates in relation to the number of hours each species spends feeding. And here it is.

... by showing that metabolism is indeed limiting at physiologically relevant combinations of body [mass] and [brain mass], our data provide evidence that metabolic cost is limiting enough to impose tradeoffs in brain evolution, and thus offer direct support for the proposition of Wrangham (Wrangham RW, Jones JH, Laden G, Pilbeam D, Conklin-Brittain NL. 'The Raw and the Stolen. Cooking and the Ecology of Human Origins.' Curr Anthropol 40:567–594, 1999; Wrangham RW. Catching Fire: How Cooking Made Us Human, Basis Books, New York, 2009) that such a metabolic limitation was overcome in the human lineage by the advent of cooking food, which greatly increases the caloric yield of the diet, as a result of the greater ease of chewing, digestion, and absorption of foods (Urquiza-Haas T, Serio-Silva JC, Hernández-Salazar LT. 'Traditional nutritional analyses of figs overestimates intake of most nutrient fractions: A study of Ficus perforata consumed by howler monkeys (Alouatta palliata mexicana).' Am J Primatol 70:432–438, 2008; Carmody RN, Wrangham RW. 'The energetic significance of cooking.' J Hum Evol 57:379–391, 2009; Carmody RN, Weintraub GS, Wrangham RW. 'Energetic consequences of thermal and nonthermal food processing.' Proc Natl Acad Sci USA 108:19199–19203, 2011). In line with this proposition, a cooked diet is preferred by extant nonhuman great apes (Wobber V, Hare B, Wrangham R. 'Great apes prefer cooked food.' J Hum Evol 55:340–348, 2008). Although the earlier addition of raw meat to the diet of earlier hominins may also have contributed to increase its caloric content (Milton K. 'A hypothesis to explain the role of meat-eating in human evolution.' Evol Anthropol 8:11–21, 1999), raw meat is difficult to chew and ingest, whereas cooked meat is easier to chew and has a higher caloric yield (Wrangham 2009; Carmody et al. 2011). Besides increasing the caloric yield and making previous metabolic limitations irrelevant, cooking would also have increased the time available for social and more cognitively demanding activities, which in turn would impose a positive pressure for increased numbers of neurons, now affordable by the new diet. We propose that the combination of a newly affordable larger number of neurons with the accompanying time now available to use these neurons in cognitively demanding tasks that improved species fitness drove the rapid increase in numbers of brain neurons encountered in human evolution from H. erectus onward (Herculano-Houzel S, Kaas JH. 'Gorilla and orangutan brains conform to the primate cellular scaling rules: Implications for human evolution.' Brain Behav Evol 77:33–44, 2011). 

This article gives me an opportunity to unpack a crucial concept in evolution that I think is lost on a great many, and to counter a few of the ideas floated in the authors' conclusion, quoted above. For example, I could remind the cooked food adherents that a circumpolar subset of the human species subsists almost entirely on raw meat, which these authors have decided is 'difficult to chew and ingest.' [I won't stoop so low as to point out to the authors and to the PNAS referees that in this characterization of raw meat the authors must in fact mean 'difficult to digest,' not 'ingest.' And since when was sushi difficult either to chew or digest?] A case in point. The people known as the Inuit in Canada, heretofore known by the derogatory label 'eaters of raw meat--or Eskimo' can ill afford to cook anything in lands that are almost bereft of combustible vegetation. [Although, I suppose, Wrangham and others would counter by saying that this would explain why the Inuit didn't invent Western, Industrialized society. They obviously lost out in that evolutionary game thanks to their diet depauperate of cooked food.]
     I could also bring up the issue of what primates actually eat, and the difference between a diet comprising largely indigestible leaves--that of gorillas, for example--and one composed largely of ripe fruit or nuts. Or, that humankind's digestive system has the architecture of a frugivore, which is what truly 'allows' shrunken guts [to quote Publishers Weekly again, but also through them, Wrangham himself]. In the same vein, gorillas do not have the gut of an obligate browser, like Bos, and thus not only do they rely on low-quality food, but also they are incapable of extracting more than a small percentage of the nutrients contained therein. If humans were to subsist on a diet of leaves, I can well imagine that we'd be chewing most of our waking lives, with nothing more material to show for it than piles of caw-caw that resemble meadow muffins or more social than a group dump site. But, enough about the Cooking 'R' Us crowd and their sometimes silly assumptions.
     The major point I want to make today has to do with the way these authors seem to be thinking about evolutionary change and natural selection. I'm talking about the idea of what's called 'selective pressure,' or more generally, 'adaptation.' In their final statement, Fonseca-Azevedo and Herculano-Houzel aver that in our fossil ancestors 'cognitively demanding tasks that improved species fitness drove the rapid increase in numbers of brain neurons' [emphasis added]. Perhaps it's just a poor lexical choice, but use of the word 'drove' in this context more than suggests that the authors believe evolutionary change amounts to natural selection for advantageous traits. Indeed, the notion that nature 'selects' anything good in a species' genome allows the authors and their compadres to make the assertions they do.

      Remember your introduction to evolution? You learned, for example, about the English moths during and after the worst depredations of the Industrial Revolution. During the time of maximum air pollution and the accumulation of what amounted to soot on tree trunks, the lighter coloured moths all disappeared and dark-coloured moths predominated. Know what was happening? No, Nature wasn't gracing the dark-coloured moths because they blended into the colours of the soot-covered tree trunks. Nature was showing its callous side by arranging it so that the light-coloured moths stood out like sore thumbs on the tree trunks where they used to blend in, and were thus being preyed on more readily, and more thoroughly than ever before, and all that was left were the darker coloured variants that had always existed, but which were always genomically swamped by the better-camouflaged lighter coloured variety. In short, evolution works by selection against, rather than for any latent or novel genetically determined trait in a population. 
     As such, I think it's clear that it's altogether misguided [nay, wrong!] to conclude that the encephalization of Homo erectus and later hominids was the result of a 'combination of a newly affordable larger number of neurons [and the] time now available to use these neurons in cognitively demanding tasks that improved species fitness [which] drove the rapid increase in numbers of brain neurons ... from H. erectus onward.' In like wise, Wrangham's major conclusion-- that 'cooking enabled hominids' jaws, teeth and guts to shrink'--is failed before it even gets off the page. Not just, mind you, for the same reason as Fonseca-Azevedo and Herculano-Houzel's thesis. Instead, there are any number of possible explanations as to why cooking might have conferred an advantage on the larger-brained hominids that were capable of using fire. One possibility that comes to mind is that spending more time making, tending, and using a fire to cook would require a sheltered and in that way protected environment, such as a cave or rock shelter, or a forest glade. That alone might have lessened the chance that bigger-brained hominids would be preyed upon. So, you see, by coat-tailing on the claims for fire use more than a million years ago [about which you know what I think], Wrangham and others have generated a host of 'just-so' evolutionary scenarios that are sufficient to explain encephalization in hominids, but which are certainly not necessary for it to have occurred.
     I'm done with cooking for now. But be relieved. I could have totally gone off on Wrangham for his ideas about Homo erectus cooking, 'table manners,' 'sexual division of labour,' 'pair bonding,' and what. ever.

* Did you ever wonder what they name the kids when two people with hyphenated last names get married? 

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Possibly an Act of Desperation. We'll See... Rule #1 Applies Here

It had been a brutally hot summer, and the earth looked as if it had been scorched even before dry lightning ignited the wilderness. The devastation covered over a million hectares. The same gray landscape stretched beyond the horizon in every direction. Blackened, leafless trees stood silent watch over nothing. No birds. No ground dwellers. Not a plant. Not a single living thing, save for the three bipedal creatures making their way up the dry valley. 
     There had never been much water in this region, where streams suddenly disappeared beneath ground, and elsewhere emerged from gaping holes in the rock. The three were stumbling up the steep hillside. Their breath was rasping, and they frequently coughed. One was spitting blood after each paroxysm of coughing. The smoke had been thick in the air for weeks as the world around them was slowly and inexorably consumed by the fire. Now they were debilitated by it, and they needed to stop often to catch their breath. 

Photo source

     They had survived the summer before the fire because there'd been many drought deaths amongst the animals in their range, and having a decent olfactory sense the three knew where to look for a feed. Precious water was available in the dead one's gut. But now even the carcasses were inedible, and whatever water their tissues once had held was either too meagre or so befouled as to make it worse than unpalatable. They seemed to be the only things moving on the landscape. And in truth they were. They alone had survived the fire because they knew the location of many holes in the rock, and had sheltered in one while the fire had burned outside. There had been a small seep in the wall of the fissure in which they'd huddled, and it had been enough to sustain them until it was possible to move about outside the hole.
     At first they could find grass seed and nuts, survivors only because of the their hardened outer coverings. Day after day they combed the ground for the insubstantial rewards. Their saving grace was no doubt that they expended little energy and never moved very far from their den. As they depopulated one area after another of the seeds and nuts, they moved further away from the hole in their search.  
     Now, at the top of a ridge the three stopped, then stooped and began scraping at the dirt with the stones that each carried. Here and there they could see the charred tops of edible tubers that had been growing just beneath the surface. The three ate ravenously whatever was left of the acrid, starchy roots, as they had now done for more than a month since the ground had cooled enough to make walking possible. They would need to return to the hole each day, since it was the only place they could get water. Without water the end would come swiftly.
     Instead the end would come slowly for the three, and in all likelihood they would die in the hole that had given them a reprieve from the inevitable. 
     
I know that the foregoing could easily be construed as a desperate act, considering that I've failed in my efforts to discover alternative natural sources for the organic compounds found in the dental calculus of the El Sidrón hominids. This left me wondering as to the possible natural circumstances under which those Neanderthals could have inhaled sufficient wood smoke for it to be recorded in the calculus adhering to their teeth, and have ingested quantities of cooked, starchy vegetables with the same effect. 
     I believe that the word picture I've painted here, rather than being the desperate act of a beaten skeptic, is not just possible or plausible, but must have been experienced by hominids throughout history. The degree to which they could survive such devastation would've been determined to a large degree by the areal coverage of the wildfire. Too widespread and the bipeds couldn't have weathered the vicissitudes of the natural world.
     Remember Rule #1: Rule out the natural before imputing your observations to the actions of bipedal apes.

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The Paleo Diet and the Question of Cooking at El Sidrón Boils Down *cough* to n-alkanes. Who Could've Predicted?

Allright! Allright! I was wrong. The last words out of my mouth on this matter were that they would be my last words on the matter. Well, I was wrong. 
     I'm talking about the Neanderthal dental calculus chemical characterization undertaken by Stephen Buckley, and which was published under the title of 'Neanderthal Medics?' [catchy title] by Hardy et al. 2012. Certain organic compounds led the authors to infer that cooked vegetables were the source. Neanderthal chefs?
     Stephen was kind enough, and a responsible enough scientist [are you listening, all who're guilty of avoiding the Subversive Archaeologist?], to confront my suggestion that he and his colleagues may have overlooked some alternative sources for the organic compounds they found adhering to the El Sidrón Neanderthals' teeth [in the form of calculus--hardened plaque]. His comments on my previous attempts, here, here, and  here, are to be found by clicking here, here, and here. [It's all enormously edifying and entertaining. You should go.]  
     Today Stephen responded to what was to have been my last word, and in his characteristically mild and amicable way, he acknowledged that insects do indeed produce hydrocarbons. Then he said something odd. Even after I quoted from a scholarly paper that mentioned finding 'a homologous series of n-alkanes (n-C21 to n-C31) [graphically cited below],

Would I Lie to You? Click here for web access.

Stephen, maven of mass-gas chromato-stratigraphic-oscopy [or something equally unpronounceable and technically so far beyond my abilities as to be completely embarrassing ], states that insects are capable of producing hydrocarbons [well known to everyone else, it would seem, besides me], however 

'...[insects] are usually accompanied by branched alkanes and alkenes too – you actually quote these in your piece. Plant wax esters, on the other hand, produce n-alkanes (and n-alkenes – these are often absent in archaeological samples, where they have undergone decay)...' [comment on Buzz Off!]

'Bummer,' I said to myself. Another beautiful theory bapped in the face by a brutal fact. I was just about ready to slink off and back into the intertubes where I belong, when it hit me. Not the fact; the anomaly. Stephen was writing as if the species of parasitic wasp about which my article was talking contained only 'branching' alkanes. ]The anomaly, by the way, is that Stephen seemed to be making a rare slip.] 'What's up with that,' I asked myself. [Such protracted conversations with myself are occurring with frightening regularity, nowadays. Maybe I'm spending too much time alone. Ya think, Rob?] 
     So, I went to check. There they were. Branching alkanes. [Who'd've thought this archaeologist would one day find himself talking about branching organic molecules?] Undaunted [or so I'd want Stephen Buckley to believe] I soldiered on. And, my perseverance paid off. I wasn't imagining it! That pesky wasp was making n-alkanes, too. 'What a trooper,' I thought to myself [more concerned, this time, that I was personifying a wasp than that I was talking to myself again]. I have the proof right here. And, it's even more exciting than I thought it was the first time!
     Immediately below I'm reproducing the table showing the actual values, by weight, of each of the compounds that were found in the wasps' Dufour glands. BEFORE you go all weird about the size of the type, chill. The table is just for show. I'll extract the important data for you. But don't be surprised by the miniscule quantities reported. Wasps are small, mind you. So their little Dufour glands don't hold much of anything--according to this table, ~332 nanograms of organic compounds [that's billionths of a gram to the SI-challenged among you]. The truly gloatable bit from this table is that ~30% of the stuff in each gland comprises...you should be sitting down, Stephen...n-alkanes. They run the gamut from n-C21 through n-C31. 30% by weight! Wriggle out of that one, Mr. biochemically savvy El Sidrón dental calculus man! 

Not bad, eh? Perhaps those El Sidrón Neanderthals weren't eating cooked plants after all. [crickets chirping]
     Moving on. Even if the vegetable-cooking inference of Hardy et al. falls flat on its face when faced confronted by the alternative, my efforts haven't made so much as a dent in their other major conclusion--that the Neanderthals were inhaling a lot of wood smoke. Gimme a break! I'm workin' on it. Let's see... Those Neanderthals prolly expired from smoke inhalation while huddling in their cave until the palaeo-firestorm was over, only the cave just concentrated the smoke and bits of it got stuck to the teeth of the Neanderthals, who were by think time gasping, mouths agape, for the last nanogram of breatheable air... [Hey, I'm allowed to make up stuff, too! Ain't I?]
      
     I'd like to acknowledge the patience and persistence that you're demonstrating, Stephen, in this protracted conversation with a total know-nothing-about-organic-chemistry type. Thanks. As for the other stuff--philosophy and absent evidence and all that--maybe some day soon we can sit down over a pint No! a Pimms No. 1 Cup in the back garden at the Wheat Sheaf in Oxford. That'd be perfect. Later.

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Spoilers! Next Up: Hardy et al.'s "Neanderthal medics? Evidence for food, cooking, and medicinal plants entrapped in dental calculus"

Phenanthrene

Fluorene

Pyrene

Fluoranthene

[Update: Please have a look at the four-part response from the biologist who undertook the chemical composition study of the El Sidrón Neanderthal's dental calculus. It's in the comments, at the foot of this post. 2012.08.21]

You may be wondering why I didn't jump on this when it was first announced. Published online on July 18 Hardy et al. claim to have extracted *cough* hard evidence of Neanderthal behaviours akin to those of modern humans from the dental calculus that formed on the teeth of 5 individuals from the Iberian Peninsula.
     I've been waiting for the time to look in detail at their claims, and although I haven't finished the fact-checking, I can say that Hardy et al.'s inferences are looking awfully shaky. As before when Very Serious Archaeologists have published chemical analyses, my focus is the authors' interpretation of their findings. I'll give but one example of this from their paper.
     They claim the following:

The additional presence [in the calculus] of the main combustion markers, fluorathene [sic], and pyrene, along with smaller amounts of fluorene and phenanthrene, strongly supports the evidence for cooking/smoke inhalation in this sample (621).      

For this exciting discovery they cite two studies: one on the chemicals produced during charcoal production, and the other on smoked salmon. Seems reasonable. No? Well, not really.
     Pyrene and fluoranthene are the products of combustion, it's true. However, they are characteristic of incomplete combustion, i.e. combustion in a reducing atmosphere--one in which there is insufficient oxygen for complete combustion to occur. That describes perfectly the 'cooking' environment only if you're producing charcoal or, indeed, smoked salmon. Phenanthrene is found in tobacco smoke and that of coal-burning appliances. Fluorene occurs naturally, and according to the EPA, '[f]umes from vehicle exhaust, coal, coal tar, asphalt, wildfires, agricultural burning and hazardous waste sites are all sources of exposure.'
     Now, remember that it was the authors' intention to produce evidence for cooking, fire, and plant use. Their inference here--that the Neanderthals were inhaling smoke-- depends entirely on the erroneous claim that the four compounds are present in the Neanderthal's dental calculus because of smoke inhalation. I have to ask, 'How likely is it that this group of Neanderthals inhaled smoke from charcoal production or salmon smoking in a reducing environment, tobacco smoke, vehicle exhaust, or hazardous waste?      
     I think you can guess the answer to my rhetorical question. But that doesn't address the possibility that the Neanderthals in question weren't dry-distilling birch or coal tar, and sniffing asphalt. After all, as the authors remind us others have made claims that Neanderthals were capable of dry-distilling birch tar and using asphaltum to haft points on wooden shafts. Why couldn't these Neanderthals have been doing just that? 
     I suppose they could have been dry-distilling birch or coal tar (if either Betula or coal were components of the El Sidrón environment--an open question at the moment). Except, if so, they'd have been inhaling the smoke from the wood fires used to 'cook' the two substances, rather than inhaling any of the compounds given off while the birch or coal were 'cooking,' because it's necessary to keep the substances being 'cooked' in hermetically sealed vessels throughout the process! Likewise, they might have been inhaling asphaltum while they were gluing a rock to a stick. But...well, I think you get the point.
     And the point is this. The authors have done nothing, not a thing, to rule out the natural sources of the chemicals they report on. And that is a subversive's take on but one of the claims made by Hardy et al. I'll have more on this cockamamy paper in a subsequent post.

     

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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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Still Waiting For Some Response From Francesco and Paul...

Berna et al. 2012 Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. PNAS online.

I'm starting to feel slighted. Tell me why I shouldn't.
     Either Francesco Berna and Paul Goldberg are so far out in the field that they're incommunicado and have been for a while, or they're too embarrassed by their fireplace faux pas at Wonderwerk Cave that they're playing it cool. 
     Paul is someone I've known for decades. I've never met Francesco. When my recent blurt on the matter called into question their claims, I expected an immediate response--so devastating is the overlooked evidence. Yet, crickets chirping was all I heard. Then I emailed Don Grayson, well-known to most of you, who was the National Academy member who acted as the editor for the paper in PNAS. He was intrigued, and thought I ought to pursue the publication route. But I thought it better to email Francesco and Paul instead, a week or so ago, hoping to stir them into some sort of response to my contention, i.e. that finding no Fourier Transform Infrared Spectrographic evidence of Berlinite in the sediments at Wonderwerk Cave can't be used to rule out spontaneous combustion of bat doo-doo in the 1.0 Myr old deposits. 

Home, Sweet, Homo erectus Home (Source):
Home is Where the Hearth Is.

     Theirs is no small inference. An Acheulian Prometheus is big news. No doubt about it! It's not the sort of thing you want to make a mistake about, especially when the mistake you're making is to ignore or to be, evidently, ignorant of the formation temperature of Berlinite [something you would have thought a geochemist and a geomorphologist might have thought to investigate before they made their claim for the controlled use of fire so long ago by Homo erectus--or H. ergaster, whichever you prefer--a species long since extinct--unless you accept that H. Floresiensis is a dwarf relict population, which I happen to do, but which is beside the point in this discussion, albeit really interesting and kewl].
     Remember that no 'hearths' were recorded at Wonderwerk Cave; the excavators instead base their inferences on the presence of heat-altered sediments across a wide area in the million-year-old cave deposits. Unfortunately, the authors report no evidence for temperatures above 550° C, and Berlinite will not form below 583° C. But then, you already know this, 'cause I've written about it here. 
     So, although I'm repeating myself, I'd like to call on the authors--either, any, or all--to respond to my question about their observations, and to comment on the temperatures required to alter the chemistry of the plant and animal remains they recovered, together with their conclusions that Berlinite would surely have been visible if spontaneous combustion of bat guano (a well-known and well-documented phenomenon) had been responsible for the raised temperatures in the cave sediments. 
     I'm waiting, gentlemen.

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