Monday, March 08, 2010

60,000 year old decorated ostrich eggshell canteens from Diepkloof, South Africa

Sometimes, it's what a paper doesn't emphasize that's the most thought-provoking and has the most far-ranging implications. A case in point is the recent paper by Texier et al. (2010) on decorated (i.e., engraved/incised) ostrich eggshell fragments from the Middle Stone Age site of Diepkloof in South Africa. The paper provides a lot of ResearchBlogging.org This post was chosen as an Editor's Selection for ResearchBlogging.orginformation about the sequence of deposits at the site, as well as on their archaeological contents. They emphasize specifically the layers attributed to the Howiesons Poort (HP), a prehistoric 'culture' associated with some of the earliest convincing evidence for symbolic behavior as well as sudden - and short-lived - technological innovation. Texier and collegaues refine our picture of the suite of original behaviors associated with the HP by presenting some fascinating data on the decorations they identified on fragments of ostrich eggshell found exclusively in those levels that date to between 58.1 +/- 1.9 and 63.3. +/- 2.2 thousand years ago (kya).

One of the real strengths of their analysis lies in the sample size they have at their disposal: to date, they've recovered fully 270 pieces of decorated ostrich eggshell, a number that dwarfs that of any contemporaneous sample of decorated objects, for instance those from the site of Blombos where only about 20 pieces of engraved ochre have been found distributed in deposits spanning about 25,000 years (Henshilwood 2009). To put this in perspective, this is less than one engraved piece per thousand years at Blombos, while the frequency of decorated objects at Diepkloof in more than an order of magnitude greater (i.e., ca. 27 pieces per thousand years), and likely much more than that in some cases, since most pieces appear to come from two stratigraphic units. What is more, as Texier et al. (2010: 1) argue, the engraved pieces from other MSA sites (including Blombos) "are characterized by a noticeable diversity of patterns, of raw materials selected for marking, and of chronocultural contexts." In contrast, at Diepkloof, "the large smaple size of EOES [engraved ostrich eggshell], its well-documented context, and the unequivocal ature of the markings offers a unique opportunity to study what constitutes the most reliable collection of an early graphic tradition" (ibid). The image below shows some of the decorated fragments in questions, as well as some of the range in engraved motifs:


Note that this is not the same figure as that illustrating the fragments in the actual paper, and they establish that the colors of the different fragments were caused by post-depositional exposure to heat and fire.

The analysis of the fragments themselves is quite interesting, and very well done. The authors document a shift over time in the predominant engraved pattern, from a 'hatched band motif' (as seen in the figure above) in the lower HP levels at Diepkloof to 'series of deeply engraved, straight, subparallel lines' in the upper levels (as seen in vignettes A and C in the figure below):

From: Texier et al. (2010): 2, Fig. 1.

The fact that Texier et al. (2010) manage to convincingly demonstrate the presence of diachronic trends in the patterns used to decorate pieces of ostrich eggshell is cool enough in and of itself (there are also two other, much more infrequent patterns that they identify). However, identifying this begs the question of why this material was being decorated in the first, and how it was used, since it clearly wasn't used as part of, say, ornaments. This is all the more intriguing given the abundance of fragments at Diepkloof, and given that the vast majority of them are very small (less than 20x20mm). An answer to this question is provided, at least partially, by the following figure comes in:

From Texier et al. (2010): 5, Fig. 5.

Texier et al. (2010: 5) indicate that the circular denting seen in both fragments above appears very similar in shape and position to the holes punctured through the top of ostrich eggs today to empty them out and subsequently use them as "a flask to store and transport various fluids, usually water" (which makes you wonder what other fluids people may have needed or wanted to carry around). In the ethnographic record, such canteens are often decorated in various ways to indicate either ownership or what was contained in it. If the analogy is appropriate, then, we have at least two potential interpretations for the meaning of the Diepkloof engravings. If one had to chose between those two, the diachronic trend described above, and the fact that there is some internal variability in both the hatched band and linear line motifs may suggest that it reflects individual 'signatures' of sorts within an accepted iconographic tradition. This is, of course, highly speculative and only one of potentially many interpretations, but no matter how you slice it, it gives us some very interesting insights in the social norms of the Howiesons Poort. Additionally, as alluded to in some of the press coverage of this report, it also provides some strong insights into how people might have dealt with climatic variability at the time to explore and exploit arid landscapes largely devoid of water. This is one of those far-ranging aspects I was referring to in my introductory sentence.

As with most reports of 'extraordinary' finds in HP levels, however, this paper also indicates that this remarkable behavioral innovation appears to have been a short-lived one (by Paleolithic standards, anyway!), and that after about 55kya, traces of such behaviors largely disappear from the record. Sooner or later, people are going to have to propose a coherent explanation for this apparently generalized pattern of discontinuous behavioral innovation. Either that, or new finds are needed to 'fill in' the long stretches of the Middle Stone Age that apparently lack the conspicuous evidence that has recently been coming to light in HP assemblages. In that light, I was pretty surprised to see Richard Klein as a coauthor on this paper, given his long-held position that convincing evidence for 'modern' behavior doesn't exist before ca. 50kya... could we be witnessing a change in perspective? I'll be curious to see how he discusses the Diepkloof material in upcoming papers...

Lastly, I have to give a Colbert-like' wag of the finger' to PNAS for its timing in publishing this paper... seriously, 60,000 year old decorated eggs! Had you waited a few more weeks, this paper could have been published in the weeks running up to Easter! I jest, of course; there's no sense in delaying the publication of a good paper, but still... I just can't help thinking about how an angle like that would have worked in the popular press!

References

Henshilwood, C., d'Errico, F., & Watts, I. (2009). Engraved ochres from the Middle Stone Age levels at Blombos Cave, South Africa Journal of Human Evolution, 57 (1), 27-47 DOI: 10.1016/j.jhevol.2009.01.005

Texier, P., Porraz, G., Parkington, J., Rigaud, J., Poggenpoel, C., Miller, C., Tribolo, C., Cartwright, C., Coudenneau, A., Klein, R., Steele, T., & Verna, C. (2010). A Howiesons Poort tradition of engraving ostrich eggshell containers dated to 60,000 years ago at Diepkloof Rock Shelter, South Africa Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0913047107

7 comments:

Maju said...

"which makes you wonder what other fluids people may have needed or wanted to carry around"

First instinctive, jokingly, thought: booze, of course.

Second, still fanciful, idea: well, beer is the typical African drink, .

Third thought: wait a moment, weren't they collecting sorghum in Mozambique about that date? Sure they did, and when I blogged about it two months ago I did consider that possibility: that sorghum was being collected for maybe something less purely pragmatic and more informal than just eating: to make beer.

Not just that, they also collected wine palm, which is also used to make alcoholic beverages.

So carrying around other stuff than mere water is not beyond the realm of the possible, even if it may be quite hard to demonstrate.

"... after about 55kya, traces of such behaviors largely disappear from the record. Sooner or later, people are going to have to propose a coherent explanation for this apparently generalized pattern of discontinuous behavioral innovation".

There was a paper last year discussing this matter. While it's pay-per-view, I got a decent impression of what they mean at Science Daily (and of course mentioned it at Leherensuge).

Powell and colleagues seem to think that there was a marked demographic growth at that time and that it was these raw numbers which pushed cultural innovation. A later decay in such numbers would have caused a decline of these complex cultural manifestations.

No 2001-style magical monolith but just people interacting with others in a more or less intense manner. It's a theory that I find quite suggestive.

glossographia said...

Seems to me that the earlier 'hatched band' motif is notably more representationally complex than the later 'subparallel lines' motif, particularly since the 'hatched band' is used in combination with actual parallel lines (as in B and I of the second plate). Do you suppose this could be related to a lessening of intensity of social interactions in this tradition between 60-55kya?

Really I just wish the media would stop talking about this as an early form of writing, and focus on what it actually represents (Daily Mail, I'm looking at you!).

Maju said...

"Do you suppose this could be related to a lessening of intensity of social interactions in this tradition between 60-55kya?"

If you ask me, I don't know. I'm not satisfied with the "property" theory that Julien seems to suggest (individual property is generally non-existent among hunter-gatherers everywhere) but I can't really explain why the changed the decorative patterns (apart from the meaningless "fashion" explanation).

Julien Riel-Salvatore said...

Maju -
re: beer, I wouldn't disagree with you, it's certainly possible, and the eggs, especially is sealed at least part of the time, would provide good vessels in which to ferment various sugar-rich liquids. One way of testing this would be to look for residues on the inside of these ostrich eggshell fragments and, if some can be found, to try to characterize them chemically. Given how socially important and relatively conspicuous alcohol production seems to have been from the very beginnings of various plant domestication economies, it certainly suggests that humans would have been aware of it much earlier.

The paper you mention by Powell et al. (2009) is a good one and does provide a mechanism to explain fluctuations in symbolic behavior. That said, it begs the question of what prompted these population density fluctuations (paleoenvironmental change is one explanation), and challenges the popular notion that these were the behaviors that gave modern human an 'edge' over other archaic populations of the Old World. This conceptual challenge is a good one to pose, in my opinion, and one that likely to force people to think about old problems differently, which is always useful.

Julien Riel-Salvatore said...

Steve -
That's a good observation... I'm not exactly sure what to make of the changing complexity of the patterns incised on those eggshell containers. This may be mitigated by the presence of two other designs in the collections ('curved lines crossing a central line' and 'cross-hatching'), each identified on single fragments, but since the authors don't indicate where these two pieces were found stratigraphically, it's difficult to say whether this is definitely the case. Certainly, I agree with you that it is no way, shape or form an analog to 'early writing.' If anything, it's probably most likely to have signified group identity rather than anything else, although some of the within-moitif variability detailed by Texier et al. suggests individuals may have had some latitude in how that identity was expressed. Getting back to your original question, though, since the amount of decoration doesn't really seem to vary much over the course of the Howiesons Poort at Diepkloof, I probably wouldn't say that the changing engraving tradition reflects less intense social interactions - maybe it reflects the development of something akin to an MSA version of minimalism!

Julien Riel-Salvatore said...

Maju -
re: the notion of property, was emphasis here was really on group identity as opposed to individual ownership , and markers of group identity are conspicuous - if sometimes expressed in rather subtle ways (e.g., projectile point shape) - in the material culture of forager groups. In that sense, I think that complete decorated eggs would actually fit in pretty well with what we know from the ethnographic record about the nature of decoration on hunter-gatherer artifacts. They could have been traded between groups of HP foragers to develop and reinforce social ties, as well as to signify group identity at a distance when exploring new territories, for instance, more arid areas as described in my original post. As I mentioned in my response to Steve above, the fact that tehre is some internal variability in how these stereotypes motifs were produced suggests that there also may well have been some individual liberties that were taken by individual engravers. What that individual variability means, and whether it is in fact purposeful, however, is open to debate and unlikely to be resolved on the basis of the evidence we currently have available.

Maju said...

"re: the notion of property, was emphasis here was really on group identity as opposed to individual ownership"...

That makes sense, yes.

However I doubt anyone is in condition to decide whether the pattern change responded to a change of the clan or tribe inhabiting the cave or a mere change on these identitarian markings along time because of "fashion" or whatever other subjective decisions that are nearly impossible to judge, right?

The fact that different communities do things (particularly symbolic things) in different ways is well established, I think, but these same communities also change customs sometimes and this process of change, of innovation, is less well understood.

"Given how socially important and relatively conspicuous alcohol production seems to have been from the very beginnings of various plant domestication economies, it certainly suggests that humans would have been aware of it much earlier".

Yes, I find it kind of ironic within human nature that maybe one of the strongest motivational triggers for the "hard work" of agriculture might have been precisely leisure... in the form of alcohol.

"... it begs the question of what prompted these population density fluctuations (paleoenvironmental change is one explanation)"...

This increase of symbolic findings appears to correlate well with the Abbassia pluvial at least at the Mediterranean (the arrival to Southern Africa seems of later date). But the question certainly remains open and, more crucially, whether there was a population decline later on that so far has not been clearly detected.

I would, very tentatively, hypothesize of punctual space-times of relatively high densities and "cosmopolitanism" along the timeline of human dispersal where such innovations could have coalesced more easily (not just because of large numbers but because of interaction between different ethnicities), with these innovations later being scattered to other areas by migration and/or cultural diffusion.

"... challenges the popular notion that these were the behaviors that gave modern human an 'edge' over other archaic populations of the Old World".

For me that's no big deal because I understand that the Asian H. erectus would have been no match for H. sapiens (much less if Toba wiped them off or almost) and that the competition between H. sapiens and H. neanderthalensis was decided not so much by brains but by legs.

What I mean is that it seems reasonably demonstrated that early UP H. sapiens tended to exploit their territories more densely and extensely than H. neanderthelensis (Gamble 2001). However, unlike Gamble I suspect that the main reason was not that Neanderthals were some sort of "ideal fathers" that spent most of their time with their children but that Neanderthals had shorter legs (and greater weight) and were hence slightly but crucially less mobile, everything else equal.

The fact that by the time that Neanderthals had colonized West and Central Asia, our species was consolidated not just in Africa but also in all the rest of Asia and continental Oceania (that's what population genetics say quite clearly), possibly also correlated to the issue of general mobility, really leans the scales in favor of our species, because when "we" began colonizing West Eurasia, "we" were already many more than Neanderthals.

And our legs were still longer.

There's another issue, which is the Cambrian Ignimbrite explosion but I think that's more like the penultimate nail in the coffin (helping Aurignacian expansion at the expense of other cultures, some of them clearly Neanderthal) than the real cause for this replacement in Western Eurasia.

And, of course there are other less clear issues such as whether Sapiens had specialized in hurling weapons and Neanderthals not... but they are less clear cut.