Part Two of There Ya Go Again! The Putative 500,000-Year-Old Hafted Spear Points From Kathu Pan 1 VS Reality: What’s the DIF?

In the previous blurt I did what I could to point out the problems with the putative spear point OSL dates from Kathu Pan 1. As promised, I’m now going to address the primary claim of Wilkins et al. 2012, that some of Kathu Pan 1’s pointy stone artifacts bear evidence of having been used as the business end of a composite armature, a projectile in fact, specifically, a spear. Let’s have a closer look at their argument. Shall we?
From ‘Evidence for Early Hafted Hunting Technology,’ Jayne Wilkins, Benjamin J. Schoville, Kyle S. Brown, and Michael Chazan. Science 338, 942-946, 2012; DOI: 10.1126/science.1227608

Wilkins et al. begin with a qualified statement of conventional wisdom regarding bipedal apes and sharp, pointy rocks.

Because Middle Stone Age (MSA) hominins and Neandertals probably both had stone-tipped hunting equipment, it is possible that H. heidelbergensis also possessed this form of technology. [Frankly, I’m surprised to see the word ‘probably’ in this passage. Perhaps the Subversive Archaeologist doth not protest too much, after all, and some of the cautionary tales I’ve spun are taking root. Then again, maybe not.]

So, the authors start from the presumption that hafted spears were commonplace in the Middle Palaeolithic. Why not, then, suppose that the last common ancestor of us and them was also capable of putting two and two together, and making a spear? No reason not to, I guess, unless you’re suggesting that there’s a gene that codes for spear-making! Never mind. The authors feel that they must say something of the kind, since they’re getting ready to tell us about stone artifacts that they believe are contemporary with H. heidelbergensis in Europe.
     As you may have read in my previous post, the early dates on the alleged spear points are irrelevant. To summarize. The artifacts in question derived from a spring vent that blew threw Stratum 4 at Kathu Pan 1 some time before the upper reaches of Stratum 4 were stripped away by an erosional process [most likely wind] and before Stratum 3 was laid down. You’ll remember that the very early dates of ~500 ka were estimates based on quartz grains drawn from the spring vent. And, of course you’ll have retained the knowledge that there is no way on God’s green earth to know whether or not the dated sand and the artifacts are in association. So, feel free to throw out the dates. It’s astonishing that the authors didn’t even flinch at the context of this collection of Kathu Pan 1 booty. And, as you’ll see, the rest of the paper is as confusing a a House of Mirrors at an amusement park.
   So, from what amounts to a lag deposit of stone artifacts and faunal remains found in a spring vent of unknown age, the authors recovered 210 pointy stone artifacts like the ones shown above. Of those, a mere 29 have at least one ‘Diagnostic Impact Fracture’ (DIF). These are of two kinds: step termination fractures (see below, item 1), occurring when a bending force is applied to the flake margin, whether that be where the two lateral margins converge (i.e. the ‘tip’) or on the margins proper. The other DIF is a burin removal [per se], which is a flake the axis of which follows a lateral margin for some distance, and terminates  in a step or a hinge fracture or simply feathers out. The first kind of DIF, the step termination, can occur anywhere on a flake margin where the thickness and brittleness are such that a small flake can be removed by a force applied from either the dorsal or the ventral direction. By definition, where pointy artifacts are concerned, the burin fracture DIF can only occur at the tip. Such forces can and do occur at the tip and along the edges of true projectile points. However, other, post-depositional processes are capable of producing such modification, including trampling by all sorts of large mammals, from bipedal apes right on up to elephants.

What’s the DIF? Step terminating fractures and burination. From Villa et al. 2010

The authors are quick to admit that processes other than projectile impact can and do create such scars. Nevertheless, they are equally quick to rule those out, first by argument from authority. They state that ‘Similar-appearing fractures can result from post-depositional processes, although their frequency within assemblages is low.’ In dismissing post-depositional processes in this fashion and for this reason, they cite one paper, by Justin Pargeter, who undertook trampling experiments to see if pressing down on some home-made flakes in an artificial substrate was capable of creating DIFs. His results are tabulated below. Those that have been crossed out are not considered DIFs, per se.

Table 1. Detailed macrofracture results from the trampling and knapping assemblages. (CT: cattle trampling; HT: human trampling. D: dolerite; Mq: milky quartz; Qtz: quartzite; BF: bifacial; UF: unifacial. Note that one tool may have more than one fracture on it). From Pargeter 2011.

     Pargeter attempted to control for the density of the substrate, and to account for differences in the strain resistance from one raw material to the next. However his efforts are a weak hook on which to hang Wilkins et al.’s sweeping dismissal of post-depositional processes. Looking at Pargeters table of results, above, you see that very few DIFs were produced during both the cattle and the human trampling parts of the experiment. He found that step terminating fractures were less common, although any comparison between single-digit results ends up inflating the differences. All up, out of 450 pieces over four trials using cattle and barefoot people, only four [count ’em, 4] flakes were found with step terminating fractures. Burination occurred on a slightly larger number, five.
     Importantly, DIFs occurred on amorphous flakes as well as pointy ones. It is for that reason, I suspect, that Pargeter concludes with the following statement.

[Diagnostic impact] fractures should only be considered diagnostic when found on pieces that are morphologically potential hunting weapon components or together with other use-wear traces.

In other words, they’re not DIFs unless they occur on pointy stones. You can forget about DIFs that occur on amorphous flakes, because, clearly, they wouldn’t have been useful for piercing hide and flesh. So. To paraphrase, it’s random and inconsequential if the flake’s amorphous. It’s okay to think that pointy rocks with DIFs are spear points. Does this sound a bit suspicious to you, too?

     Albeit Pargeter’s experiments were carried out in good faith, their shortcomings aren’t trivial. For example, we know that substrate density will have a bearing on damage from trampling–for example, between sand and bedrock. Every kind of substrate in between sand and rock will yield a different result, as, moreover, would the size of the animal doing the trampling. Presumably giraffes, rhinos, and elephants would be capable of inflicting more damage to all sizes and shapes of flakes than cows or people. In the case of Kathu Pan, one can imagine that the water-seeking animals that congregated when there was standing water wouldn’t have been restricted to people and cows [or gnus, for that matter]. Nevertheless, Wilkins et al. think it’s quite all right to play down the role of trampling on the basis of Pargeter’s single experimental effort. This, as much as anything, gives lie to the remainder of Wilkins et al.’s paper.
     Following their near-effortless dismissal of post-depositional processes, Wilkins et al. report on their own experiment, to demonstrate the kinds of modifications that can occur when a pointy bit of rock is thrust with force into a small dead animal (see previous discussion for a graphical representation of these experiments). In that experiment, 106 trials were successful in penetrating a dead springbok. And how many DIFs resulted from 106 penetrations? A total of 9 points incurred DIFs (i.e. in about 8.5% of the total of 106 trials). So, you gotta hand it to the authors, the experiment was successful in producing DIFs by spearing a dead wild animal, despite the small percentage that displayed damage characteristic of spearing something. Those same 106 trials produced 5 points that suffered ‘crushing’ (i.e. 5% of the trials), which one must presume occurred at the distal tip. Fully 16 times out of 106 the experimental points suffered no damage (i.e. 15%). There were 2 snap fractures (i.e. about 2% of the trials). The residual trials, those which resulted in no notable outcome, make up the remaining 70%. It’s also satisfying to note that their hafts failed 12 times (i.e. in about 11% of the trials). [Bites tongue, blood drips from corner of mouth. If you’ve ever looked at the butt/proximal end of a great many Mousterian points, you’ll know that they’re practically unhaftable–at least compared with the bificially thinned sort that modern humans produce whenever they want to haft something.]
     Now, as most of us are aware, replicative experiments demonstrate that a phenomenon can occur as a result of a particular set of actions. Nevertheless, they do nothing other than to suggest the means by which that phenomenon might occur. It’s a hypothesis. A starting place. Sufficient to explain the phenomenon of interest, but by no means necessary. Thus, while great fun, the authors’ experimental results are patently inconclusive, and oddly have very little bearing on their thesis. In addition, no amount of statistical tap-dancing can replace the kind of contextual evidence that would readily indicate the use they propose for such artifacts–a point embedded in an animal bone, for example, or, at a minimum, one associated with the remains of a carcass in an unequivocal manner.
     True, Wilkins et al. did find the KP1 points in association with animal bones. But, as I pointed out in my last outing, those items almost certainly came together as the result of post-depositional processes, and there can be no no way of knowing if the bones and stones were in association when the animals died or the stone points were discarded or lost. In this, I have to say, the authors’ naïvete is breathtaking.
     Perhaps knowing that their arguments were thin, they conduct one further analysis. They decide to look at plain old damage, rather than DIFs, as a means of diagnosing spear points from cutting tools. Apparently, in addition to the damage categories discussed above, the authors found a considerable amount of simple ‘edge damage’ on their experimental pointed flakes. Here, they think, is a means of getting at the function of the KP1 points without even bothering with DIFs (which, you’ll remember, were meant to be the diagnostic damage that sorts mere flakes from projectile points. Their analysis gets weirder by the minute.

… we recorded the macroscopic edge damage that was evident on all complete points… . Edge damage was more frequent at point tips than along point edges, and distributions were similar between left and right sides (Fig. 4A [reproduced further down]).
     Taphonomic processes can be ruled out as the sole source of damage on the KP1 points. Post-patination scars, which are easily identified … [see below], reflect damage not related to use of the points and occur as frequently on point edges as point tips (Fig. 4B). In aggregate, the damage along the dorsal surface of the KP1 points was similar to the distributions of post-patination scars … whereas the damage along the ventral surface was different… Therefore, we focused on the ventral edge damage to test hypotheses about the function of KP1 points.

From Wilkins et al. 2012
From the look of the chip indicated in D, above, the ‘post-patination’ scars could easily have been made yesterday, the result of trowel trauma or the banging around that the artifacts must have experienced as the spring was bubbling through Stratum 4 at some unknown time in the past. And, is it just me? Or, do the authors plain fail to adequately explain why they focussed on ventral damage? It sounds to me as if they’re saying, ‘There’s no differences on the dorsal surface that’ll allow us to distinguish between natural and artificial edge damage. However, we see differences on the other surface that do, sort of, therefore we’ll only include the ventral damage in our analysis.’ Huh? I know. We should just write them off right here. But, whadda ya say we give ’em the benefit of the doubt for now.

The illustration above depicts ventral edge damage to 106 of the loverly, pointy flakes–the complete KP1 points. Columns A and B are meant to show us that there is a ‘real’ difference between the locations of pre-patination edge damage (A) and those that occurred post patination (B). The authors recorded an extraordinary amount of damage on the KP1 points–an average of 38 scars per flake! The total of 1,973 in A are considered the result of use, and the 2,145 in B are said to be ‘post-patination’ [or, irrelevant to their analysis]. Notice that in A, a greater degree of use damage occurs distally than either the post-patination damage (B) or that of the presumed cutting tools from Pinnacle Point 13B.
     The authors favourably compare the degree of distal damage between KP1 points and that occurring on their 32 experimental stone points. They see this as proxy evidence that the KP1 points were used for thrusting into live hide and flesh. But, in fact, the experimental flakes sustained an average of only 21 edge-damage scars each. This is no doubt significantly different, statistically speaking, from what the KP1 points experienced in non-post-patination damage. If we are to accept that the spearing experiment is a proxy for what the KP1 points went through during their use-lives, the difference between the two samples in numbers of edge damage events suggests the real possibility that the 17 additional scars suffered by each KP1 points may indeed have been post-depositional, but pre-patination, something that the authors never consider. Instead, the authors seem very keen to focus on the predominance of damage to the distal tip as a means of diagnosing a spear point.
     In all of this focus on edge damage to the exclusion of DIFs, the authors make no mention of the type of scarring–i.e. the morphologies–of the edge damage. You’d have thought that, if one class of damage were qualitatively different from the other there might be more reason to suppose that the differences were due to the different functions for which the points were intended. Especially curious is that the authors make no mention of the most likely reason, in a physical, mechanical sense, for both a qualitative and quantitative difference between edge damage on the dorsal surfaces of the KP1 points and that visited on the ventral surface. I’ll explain.
     Think of the cross section of the vast majority of MSA (Middle Palaeolithic) unifacial lithic flakes, which is how the authors describe their KP1 points. Those shown below are some ‘blades’ from Qesem Cave. Notice the ventral surfaces–the smoothly curved lower sides in the cross sections of examples 2 through 10. The ventral surfaces of these flakes would naturally be much more susceptible to edge damage in comparison to the dorsal side. That’s because of the additional mass on the dorsal side, which provides a natural buttress against bending force. Ask any knapper. A much greater force would be required to remove a flake from the dorsal surfaces of any one of the examples.

Notice how the dorsal surface is buttressed by the dorsal mass relative to the ventral. From Shimelmitz, Barkai, and Gopher 2011.

With this in mind, one is tempted to ask, ‘Other than the authors’ preference to view their data in whatever way they choose, why should we accept as a given that the thousands of scars inflicted ‘post-patination’ were the result of a completely different set of processes than those scars that they say are the result of use?’
     By now you should be as suspicious as I am about the veracity of Wilkins et al.’s claim to have found evidence of hafting and use of pointy rocks as projectile points. After all, a litany of shortcomings attends this paper. First, they have failed to accurately date the finds. Second, they have failed to imagine a wide enough range of possible sources of damage. Third, they have failed to take into account the greater natural susceptibility of ventral surfaces to incidental chipping compared to that of the dorsal. Fourth, they have failed to give a good reason as to why they didn’t include dorsal damage in their calculations, other than to aver that dorsal damage wasn’t diagnostic or otherwise helpful. But, on what grounds, one wonders? There are no data provided. I believe strongly that we should be allowed to judge for ourselves on this point, yet we’re given no help whatsoever by the authors.
     Once again I’m forced to say, as I did relative to Wilkins’s earlier article on the putative ‘blade industry’ at Kathu Pan 1, that the data presented are inadequate to support this latest, even more spectacular claim to have found evidence for composite tools deep in the Middle Pleistocene of southern Africa. This is going to be my last word on the subject. Promise.
     Sorry. Can’t resist. One more word. I find it sobering that the Science referees failed to notice even one of this paper’s methodological and analytical shortcomings. But then, I guess we should be getting used to that, by now.

Thanks for dropping by! If you like what you see, follow me on Google Friend Connect or Twitter, friend me on Facebook, check out my publications at Academia, or connect on Linkedin. You can also subscribe to receive new posts by email or RSS [scroll to the top and look on the left]. And please don’t forget. Oh, and you can always put me on your blogroll! By the way, I get a small commission for anything you purchase from if you go there by clicking through from this site. 

There Ya Go Again! Part One–The Putative 500,000-Year-Old Hafted Spear Points From Kathu Pan 1 VS Reality: What’s the DIF?

It’s now officially an international media feeding frenzy. –  Stone-tipped spears used by human hunters much earlier in time
National Geographic –  Stone Spear Tips Surprisingly Old—”Like Finding iPods in Ancient Rome”
Science News – Oldest examples of hunting weapon uncovered in South Africa
New Scientist – First stone-tipped spear thrown earlier than thought
Daily Mail – The birth of weapons: Researchers discover man began hunting with stone …
Voice of America – Archeologists Identify Oldest Spear Tips
Scientific American – Human Ancestors Made Deadly Stone-Tipped Spears 500000 Years Ago
Christain Science Monitor – Gone spear hunting: Ancestors used stone spear tips 500000 years ago
Times of India – Man began spear-hunting 200000 years earlier than believed
U.P.I. – Stone-tipped weapons older than thought
Vancouver Sun – Scientists spear animals to make point [my home-town newspaper. *sniff*]
China Post – Early human beings used stone spear points at least 500000 years ago: experts
Windsor Star – Spear study gets to the point
The Independent – Prehistoric arms race started earlier than previously thought
The Daily Telegraph – Man hunted with spears half a million years ago
News 24 – SA spear tip made by earlier ancestor
The Seattle Times – Prehistoric man became deadlier earlier than previously thought – Stone Spear Tips Suggest Weapons Were Developed Much Earlier Than Previously Thought
Science News – Archaeologists Identify Oldest Spear Points: Used in Hunting Half-Million Years Ago
Business Week (!) – Prehistoric Man Was Deadlier Earlier Than Once Thought – Study: Stone spear tip made by earlier ancestor

From Wilkins et al. 2012
This is beginning to feel like one of those squirmily popular horror series like Hallowe’en. You know? Freddie of the long fingernail knives. A tip o’ the hat to Physorg for pointing us in the the direction of the November 16 print edition of Science, where one finds this:

Evidence for Early Hafted Hunting Technology,’ Jayne Wilkins, Benjamin J. Schoville, Kyle S. Brown, and Michael Chazan. Science 338, 942-946, 2012; DOI: 10.1126/science.1227608

Yes, sports fans, the same Jayne Wilkins who gave the Subversive Archaeologist fits a while back [here, herehere, and here] with her claim of a ‘blade industry’ at Kathu Pan 1 in South Africa. It’s also the same Kyle Brown who was the lead author on the Pinnacle Point microliths and ancient heat-treating of lithic raw material. [South African archaeology is obviously a closely knit community.] These latest claims from Kathu Pan 1 are made for stone tools recovered from the same site as the earlier ‘blade industry,’ an infilled sinkhole, or doline. This time around, some pointy artifacts with step fractures on the distal (pointy) end and huge proximal (butt) ends are claimed to be evidence for, as the title would suggest, composite tools. And, once again, the claim is made for a VERY early date, and I quote ‘~500 ka, coeval with H. heidelbergensis [or H. antercessor, if you prefer].’
     I hope you’ll forgive what will undoubtedly end up being a very long blurt this time around. It’s dead necessary. If your Subversive Archaeologist is going to spot shortcomings that undermine the arguments made in a paper like this, he’s going to have to spend way more time, and marshall ten times the breadth of expertise than did the referees. And, remember, these are Science referees. There’re no flies on them [at least in the opinion of the Science editor(s)]! So, this is not a task that lends itself to brevity.

Vicinity of Kathu Pan 1 (from Wilkins et al. 2012). 

The authors are well aware that such claims cannot be made simply by bold assertion. In today’s case, the extraordinary conclusions are accompanied by some truly impressive morphological and metrical analysis, and actualistic experiment with a purpose-built crossbow, some hafted spear stand-ins, and a deceased wild springbok [small ruminant artiodactyl]. Unfortunately for the clever archaeologists, the basis of their claim rests not in their analysis, but rather in their arguments. It’s the same old story that the Subversive Archaeologist has told before. Funny thing is…few, it would seem, are listening. Maugre their ultra-scientistic approach.

Notice the veritable totem pole used to ‘analogize’ a throwing weapon. The ‘business end’ is a flake hafted to a 1-1/8″ (2.8575 cm) clothes-closet dowel, inserted into a piece of 1″ galvanized pipe joined to a piece of 1-1/4″ pipe. Not that it makes any difference to their conclusions, but this is less analogous to a javelin than it is a small tree-trunk! (From Wilkins et al. 2012)

I’ll save my mirthful response to the use of a springbok for such an experiment for a quiet moment alone in my mother’s basement. But, seriously, unless the thing were lying dead on the pan, can you imagine H. heidelbergensis [or you or me, for that matter] sneaking up on a nimble beast like this one and driving home such a weapon? They might as well have chosen a dead elephant [but that might not have impressed the authorities].
     This article has two major shortcomings, as I see it. The first is in convincing a sceptical archaeologist that the dates are from contexts in which the association with artifacts is well-warranted. Their second mistake comes in the background knowledge that they draw on in making their claim that the only way their bits of stone could have been modified in the way they were because they were hafted to a stick and poked into an animal. I’ll deal with the dates in this part; the stones themselves will have to wait.
     Wilkins et al.’s troubles have their origin in the Kathu Pan 1 doline’s depositional history, and in their evidently weak expertise in interpreting the depositional agents of various sized clasts. There is no indication that the authors are even aware of the potential for mixing in a sediment trap like the one in which they’re excavating, much less the action of the occasional spring that came into being during the site’s depositional history. The authors appear to treat each excavated artifact and sand grain chosen for OSL [yup, again] as if they had been, for all time, temporally associated. How else could you explain their naïve acceptance of the OSL age estimates?

Filled circles are OSL age estimates; filled triangle is U-series/ESR age estimate. From Wilkins et al. 2012.

To get the critical ball rolling, check out the schematic excavation profile above. The authors describe the sediments thusly:

From top to bottom, stratum 1 [not shown] is characterized by 1.5 -2 m of interdigitating calcified sand and organic peats. Stratum 2 [not shown] is characterized by well-sorted aeolian sand that becomes increasingly calcified toward the top. Artifacts in strata 1 and 2 are very sparse, but Beaumont tentatively suggests a ceramic LSA or Iron Age designation for stratum 1 and potential Robberg affiliation for stratum 2.

In other words, too young to be of interest to the authors.

Stratum 3 is … gravel with sub- angular to sub-rounded pebbles in a greyish sand matrix. 

Stratum 3 is dated at 291 ka.

Stratum 4 consists of two substrata, 4a and 4b, which are distinguished from each other based mainly on the lithic and faunal assemblages, though Beaumont … also reported a thin pebble lens that divided the substrata. The artifacts were recovered from a yellowish sand matrix.

Stratum 4 sounds like well sorted sand. Most probably wind-borne. In fact, I’d bet my lower central left incisor that these are fine to medium-sized sand grains, typical of aeolian transport and deposit. [I should tell you that I can make good on this bet. The orthodontist that the tooth be extracted before they put braces on my pearly whites, and I still have it under my pillow, waiting for the tooth fairy.] Moreover, I’d bet that the period during which the sands were deposited was an extraordinarily dry and windy one. That’s because there is evidence of what could only have been scouring out by wind in the non-conformity between 4 and 3. Stratum 3’s coarser, unsorted sediments bespeak a later, wetter period when surface water flow was transporting a range of small-sized sedimentary grains into the doline.
     But, here’s the kicker. The really old dates are from an intrusive geomorphic feature, one that would undoubtedly have brought older fine sediments up to the level of the excavations, and described by the authors as follows.

In the process of cleaning the section, two well-defined vertically-oriented spring vents in stratum 4a were revealed and described as the ‘Upper Vent’ and ‘Lower Vent’. The Upper Vent, which is in the uppermost levels of stratum 4a and truncated at the top by Stratum 3, is densely packed with lithic artifacts and fauna, and the area outside the vent contains few, if any, artifacts. [The 464 ka sample] was recovered from sediments in direct association with the concentrated lithic artifacts and faunal remains within the vent. 

What does this tell us? And how does this relate to the veracity of Wilkins et al.’s claims? Plenty.

A brief accounting of karst features.

To begin with, think of how a big hole in the ground [the doline] came to be, and then filled up. There’s a clue in the name of the site, Kathu Pan. A ‘pan’ is what would be called a playa in North America. It’s a broad, nearly horizontal valley bottom that seasonally collects water from precipitation, hosts a shallow lake for a time, then dries up and awaits the next wet season.
     For a doline to form, the pan must be underlain by lithified fine sediments, such as limestone, siltstone or mudstone. These are the kinds of geological strata that are susceptible to karst processes–cave formation, among others. The illustration above is a succinct depiction of the kinds of geomorphic features that can occur in areas of karst. Those below are real-life dolines.

Guatemala City, Guatemala, 2007. A ‘swallow hole.’ It will need to be bridged. Filling it in is out of the question.
Florida. This is more of a ‘sink’ than a sinkhole. But just as devastating. 

A doline [or sinkhole] is the surficial expression of a subsurface void, or cave, the ‘roof’ of which became too thin near the surface and collapsed. Sinkholes are common in the middle of the US, and anywhere that the bedrock can be dissolved by surface water percolating downward. [The Santa Cruz campus of the University of California, where I’ve worked for the past 8 or so years, is built on mudstone that hosts a cave system, and in many places there are sinkholes at the surface.]
     So, once formed, the Kathu Pan 1 doline and its associated solution features began to fill in with any sediments that were transported by wind or water to its gaping maw. According to the authors, the pan in question is still somewhat depressed relative to the surrounding surface, and is thus still filling in. [It’s likely that, as the underlying bedrock evolves, voids get larger, leading to settling of the fill material. Thus, a feature like the Kathu Pan 1 doline will always be a dynamic sedimentary environment, and might never be, truly, filled in.]
     The basal geology of Kathu Pan 1 would be of no intrinsic value to this discussion of the OSL age estimates were it not that Wilkins et al. observed ‘spring vents’ in their site. Your subversive imagination should, upon hearing such a statement, see a red flag. A spring vent is an opening in the surrounding sediments that concentrates ground-water discharge to the Earth’s surface. In other words, it’s like a do-it-yourself geological pressure release valve. In the case of Kathu Pan 1 these spring vents could only have occurred at a time when the underlying karst system was chock full of water under pressure from the local water table. Some of that pressure was relieved through a ‘vent’ that formed in the unconsolidated sediments of the doline’s fill. Think of it. Everything in the vent would be turned into a slurry as the water passed through it toward the surface. As in any transport process involving moving water [even water moving vertically through sediment] the smaller and lighter clasts would be more mobile, and the heavier pieces would tend to form a lag deposit. [Exactly fitting the authors’ description: ‘concentrated lithic artifacts and faunal remains.’] In a vertical column that contains fines like sand and larger pieces like stone artifacts, the heavier artifacts would literally sink as the smaller grains were randomly removed from beneath them–just the way your feet sink when you’re standing on a beach and a wave washes ashore and then recedes.

     It simply can’t be argued away or ignored. The authors’ concentration of artifacts and faunal remains is almost certainly the result of the these processes I’ve described. I’m not makin’ this stuff up! Karl Butzer, one of the lions of geoarchaeology in the early days, thought that a spring vent was an important enough disturber of archaeological traces that he put a wonderful illustration in Archaeology as Human Ecology, shown below.
     So, quite apart from the claims of hafted stone artifacts, the authors have a big problem with their dates. If it isn’t already patently obvious [and there’s no reason it should be] the dates from Stratum 3 and the spring vent are suspect. We have no way of knowing the stratigraphic origin of the coarser sands and pebbles in Stratum 3. All we know is that they came from somewhere else further up the fluvial train. They could have been eroded from the older sediments in which the doline formed, or any deposit created since then. How to know? [More OSL mathematical flim-flammery, I suspect.]
     In a different way, but with the same result, the fines selected for OSL dating from the spring vent were undoubtedly a porridge of old and young clasts. Since the water was pushing upward through older sediments, we can have NO WAY OF KNOWING where they came from or indeed how and if they are related temporally to the artifacts that almost certainly derived from a younger level or levels. The spring vent could be as recent at Holocene in age, given the other uncertainties raised by the depositional circumstances in Stratum 3. Bottom line: we could never know the true age of any artifact in the spring vent that passed through Stratum 4 (a and b).

There is no question that a spring vent, such as that occurring at Kathu Pan 1, would wreak havoc with the sediments in its path, and those nearby.

I’ve raised a lot of questions in this piece. So, to summarize, the OSL dates from Kathu Pan 1 cannot be relied upon. Because of the depositional environments–a sinkhole and a spring vent–there are too many unknowns when it comes to the association between the artifacts that interest the authors and the sediments selected for dating. Too. Many.

     I’m truly sorry if this comes across as a harangue. I get so frustrated by the way people working in my business are so concerned to get a spectacular result that they ignore very basic principles of stratigraphy and geomorphology, to say nothing of informal logic. The present authors are no exception [as we’ve seen before].
     Watch this space for a discourse upon the stones, coming soon.

Thanks for dropping by! If you like what you see, follow me on Google Friend Connect or Twitter, friend me on Facebook, check out my publications at Academia, or connect on Linkedin. You can also subscribe to receive new posts by email or RSS [scroll to the top and look on the left]. And please don’t forget. Oh, and you can always put me on your blogroll! By the way, I get a small commission for anything you purchase from if you go there by clicking through from this site.