Why No 14C Dates for Blombos Cave’s MSA? Not Lobbing Aspersions. Just Sayin’ …

If I were a chess player I probably wouldn’t be trying this gambit. But I’m not. So, bear with me.

Worked bone, stone and ochre from Blombos Cave (Wikipedia)

I need help with a question that’s been nagging me for years. I’m curious to know if any of the bone artifacts from the Middle Stone Age (MSA) layers at Blombos Cave have been directly dated using AMS 14C. From my reading it appears not. In fact, it looks as if 14C was abandoned in favour of luminescence techniques once they had excavated deeper than those layers identified as Late Stone Age, the earliest of which were dated to give-or-take 39 ka BP. Everything below that is deemed to be MSA, and organic materials such as charcoal and bone were passed over in favour of grains of sand or burned flints in those strata. 
     Remember that, for most of us, MSA is synonymous with the Middle Palaeolithic in the rest of the world, and, for better or worse, it’s exclusively associated with the Neanderthals and their ilk, for which the jury is still out as to their cognitive equivalency with us modern types. Finding what are clearly modern human artifacts at Blombas Cave and elsewhere on the order of 30 to 50 ka earlier than anywhere else in the world has stunned and amazed scientists from Barrow to Burbank. But it’s never sat well with me. 

Location of Blombos Cave, South Africa (Credit)

     You and I know that 14C is perfectly capable of accurately gauging the age of organic materials until at least 50 ka, notwithstanding the need for calibration that corrects for environmental  and other effects. Why then do we have only luminescence age determinations for the sediments in which the Blombos Cave bone artifacts and charcoal were deposited? Henshilwood et al. (2002) provide some insight, although I’m not certain they realize that by doing so they’ve left themselves exposed to (at a minimum) questions about their decision.
     That (to me) curious decision is explained in what amounts to a throwaway comment, which I will quote here

In radiocarbon terms, the MSA at BBC is of infinite age (Vogel, personal communication).

The MSA levels are being dated using luminescence techniques: single-grain laser luminescence (SGLL), single aliquot optically stimulated luminescence (OSL and IRSL), multiple aliquot OSL on sediments and also TL of burnt lithics and electron spin resonance (ESR) of teeth (Henshilwood et al. 2002:638). 

Being the skeptical type, I was intrigued by what seemed to me to be such a weak citation as to the inefficacy of 14C beyond 39 ka–the date of the oldest LSA at Blombos. Just a ‘Vogel pers. comm.’ No reams of empirical evidence. No other justification. So I endeavoured to discover by what authority Vogel had made such a pronouncement.
     No doubt some among you will think it naïve of me, or worse, that I’m poorly informed and ill-prepared to be taken seriously by the palaeoanthropological establishment. Nevertheless, I had no prior knowledge of Vogel’s reputation in the radiocarbon world and in the South African archaeological community. His work includes a 1997 paper in Radiocarbon in which he attempted to calibrate 14C dates with U/Th dates within the same stalagmite from a South African cave. That work was superseded a few years later by the more widely cited Fairbanks et al. (2005), who honed the 14C calibration curve back to 50 ka using pristine corals from around the globe. Their findings are that 14C underestimates calendar years such that 45 RCYBP works out to 48,934 calendar years (give or take 500). By this means the calendar date of 39,200 BP from the lowest LSA level at Blombos would have been produced by a radiocarbon age of about 34 ka RCYBP (try it yourself by clicking here to go to Fairbanks’s calibration calculator).
     It would seem, therefore, that despite Vogel’s pronouncement, cited in Henshilwood et al. (2002), there is no physical limitation on dating organic material that is older than 39 ka (i.e 34,000 RCYBP), as long as its age doesn’t exceed 45 RCYBP. That would, theoretically, allow the excavator of Blombos Cave to extend use of 14C for at least a further 11,000 RCY beyond the earliest LSA from Blombos Cave. Surely some of the MSA materials could be presumed to date from this 11,000-year window.
     Directly dating the bone and charcoal from the upper MSA strata may prove nothing. However, knowing that there’s no theoretical limit on the use of 14C for that 11,000 year period leaves wide open the question as to why Chris Henshilwood hasn’t attempted to date, directly, some of his bone artifacts or charcoal from the MSA layers. It’s just possible that they would yield dates far younger than those produced by luminescence techniques (about which I’ve had a certain amount to say in previous efforts here at the Subversive Archaeologist).

From Henshilwood et al. (2002)

     After all, the MSA levels in Blombos (at least those illustrated in Henshilwood et al. [2002], shown above) appear to be quite shallow–the sort of depth that you could imagine accumulating in far less than the 35 ka that the luminescence dates would have you believe it took for them to accumulate–and it’s within reason to suspect that they could easily have been deposited in the 11 RCY or so before 39,200 BP.
     And so. For what it’s worth, I’m issuing a challenge from this lofty perch of mine. Chris, try dating some of your MSA bone using good, old-fashioned, AMS 14C and see what you get. A fair few of us are curious to know the result. 

Iain Davidson Guest Comment: Seafaring Neanderthals?

I’m very pleased on this Friday to introduce the Subversive Archaeologist‘s good friend, Iain Davidson. He has a few words to say about the just-announced claim that Neanderthals were paddling around the Ionian islands in boats even before boats were invented. 
     But before I turn you over to Professor Davidson, I think it only host-worthy of me to give you a little bit of his background and, I suppose, his credentials for commenting on Ferentinos, et al.’s ‘Early seafaring activity in the southern Ionian Islands, Mediterranean Sea’, the latest bit of real archaeological science from the Journal of Archaeological Science‘s Very Serious Referees and Editors.
     Since before he and I became acquainted in about 1988, Iain and I have shared what I facetiously refer to as an ‘intellectual pathology.’ We both think that a lot of the claims for modern-human behaviour in the Middle Palaeolithic are misguided at best, misinterpretations for the most part, and, at worst, mythical.

Iain Davidson

     Iain has recently retired from his Professorial duties at the University of New England, in Armidale, New South Wales, where he plied his trade for several decades. His research and fieldwork have spanned the length and breadth of Australia, from the dream time to the European occupation. He has expertise in, among other fields, animal bone archaeology, taphonomy, lithic replication and lithic analysis (including having to do with the Near Eastern Middle Palaeolithic). He has published a good number of books, including a ground-breaking treatment of cooperative ties with Aboriginal groups. But the ones that are most closely connected with our favorite subject are one on the evolution of cognition and language and another on the relationship between lithic ‘technology’ and how we became human. [By the way, Iain, I had to put technology in inverted commas, because technology is a word that implies mindedness, and as you know, it’s still an open question whether it existed throughout the history of stone artifact production.] If you check out the Subversive Archaeologist‘s Emporium, you’ll see Stone Tools and the Evolution of Human Cognition, and a ‘little’ volume titled Human Evolution, Language, and Mind, which has been virtually ignored by all the wrong people, who seem disposed only to listen to Very Serious linguists like Steve Mithen. Iain and co-author William Noble got it right–I won’t say the same for the competition. So, as you read Iain’s comments, keep in mind that he’s seen more lithics in situ, and studied the archaeology of Europe and Australia for more years than you and I’ve had hot dinners [that last bit might have been a slight hyperbole]. 

I received this from Iain this afternoon, after what was surprisingly little prodding. 

This is a very careful study of the bathymetry by a team well qualified to do that. I am less certain that the authors are on top of the issues about archaeology. But we are used to that by now. What can possibly be difficult about archaeology? So let us ask some questions.

Where are the artefacts? One of the island sites is said to be Lower Palaeolithic. My antennae immediately send me a signal. How are these artefacts being attributed? It is, by now, well established that it is not as straightforward as it once seemed to attribute surface finds to any of the subdivisions of the palaeolithic. What is needed is well-stratified finds from well-dated strata before we can go from ‘There are some flakes here which do not look like Upper Palaeolithic blades’ to ‘These are Mousterian artefacts’ to ‘These artefacts date to the same date as Mousterian artefacts on the mainland’ to ‘These artefacts were made by Neandertals.’  In each case there is an inferential leap that is not substantiated. 

My question would be ‘Are there no artefacts that look like these in any of the Upper Palaeolithic assemblages?’ My guess is that there are, but that, as elsewhere, they have been ignored because of the dominant expectation that Upper Palaeolithic industries consist of blades. In the absence of even one illustration of artefacts it is impossible for anyone to know whether the attribution is reasonable. Even if the authors are qualified to be wedded to the inevitability of the Lower, Middle, Upper Paleolithic sequence, they need to establish the veracity of their claim that the occupation was genuinely a) Mousterian and b) of the same date as the Mousterian on the mainland and c) that only Neandertals made Mousterian assemblages (well, at least we know the answer to that–skeletally modern humans made Mousterian assemblages at Qafzeh in the east Mediterranean).

Finally, because this has been an exhausting week for silly claims about archaeology by people unqualified to make them, the maps are disturbing.    Figure 8 looks as if the short crossing between Lefkada and Kefallinia when sea-level was -120m was in the order of 2-3km.

Fig. 8. Palaeoshoreline reconstruction when the sea level was at —80 and
–120 m showing the most likely used short range route crossings to the islands from Middle Palaeolithic to Mesolithic. P: Peloponnesos, AA: Aetolo-Akarnania, IZ: Zakynthos Island, IK: Kefallinia Island, IL: Lefkada Island. [From Ferentinos, G., et al., ‘Early seafaring activity in the southern Ionian Islands, Mediterranean Sea,’ Journal of Archaeological Science (2012), doi:10.1016/j.jas.2012.01.032]

 The question we need to be asking is: what sorts of water crossing were possible for hominins at different times. I have always championed the importance of the sea-crossings that brought people to Australia. (And forgive me a moment’s rage–there are some quite good sources about this published by people who actually know something about Australia. Why do European scholars think that the only good source is a European one?) But the point is that to make those crossings, watercraft did need to be constructed, because to get to Australia several crossings were needed and one of them was more than 70km. But the point I have tended to neglect is that there were also rivers to be crossed on the way: at very least the Nile, the Euphrates/Tigris and the Ganges. How wide were these crossings and how were they made? If we accept all of the other unsubstantiated assumptions involved in this paper, we may simply be looking at crossings that must have been commonplace at the time modern humans were moving out of Africa.

Iain Davidson, March 3, 2012.

He’s wired into the comments, so fire away. And may the best paradigm win!