Sunday, March 04, 2012

Shake your (Acheulean) money maker

There was a paper presented by Mimi Lam at the last AAAS meeting in Vancouver and which was covered in LiveScience last week and has bit causing something of a stir (and it spells Acheulean correctly!). While I'm always leery of relying only on press reports to make sense of unpublished papers, its abstract is available online and provides a bit more info. In a nutshell, one the arguments of the paper is that by the Middle Pleistocene, handaxes might have been used as a form of currency. I've talked about handaxes before on this blog, along with some of the debates about what drives their morphology - the focus is often on their alleged symmetry and the fact that this feature might not have been purely functional.

I wasn't at the AAAS meetings, so I didn't hear the paper. All I've read so far are the LiveScience piece, the abstract, and a very thoughtful blog post by Rosemary Joyce in which she rightly points to the at the tangled ball of conceptual yarn that money or currency represents from an anthropological standpoint. Definitely worth a thorough read.

My main concern about the study, however, has to do with the handaxes themselves. There is this notion (often repeated in archaeology textbooks) that they can be very symmetrical, and that the overall degree of symmetry in handaxes increases over time. Frankly,  I don't think we can safely assert this at all. Sure, handaxes can be symmetrical on occasion, no question there. But to my knowledge, this remains a very qualitative impression based on selected samples of handaxes, with selection operating both on the geography and age of the biface samples being observed, as well as on the fact that these samples themselves can be selected for. By this, I mean what gets considered a handaxe/biface and considered in these studies about their symmetry (and what the controls are to evaluate what is 'unnatural' symmetry in various contexts), and how that can vary across analysts and studies.

The main problem with the 'time-vectored increase in handaxe symmetry' as I see it is this: to the best of my knowledge, this hasn't been demonstrated empirically to hold true across all of the Old World. Yes, this seems like a fairly tall order. But this is the scale that is implied by this view. Based on my own biased view and experience with handaxes (and I've looked at a few), the opposite could even be said: there is no fundamental change in the degree of symmetry in handaxe assemblages over time - symmetry is a contingent variable determined by factors like blank size and shape, reduction intensity, use-life, technical skill, and maybe social considerations - the social dimensions being the hardest of all to establish objectively, let along attribute a function to. So, if this idea is not demonstrated, any interpretation of handaxe function based on symmetry is also potentially problematic.

I was talking about this with a colleague on Friday, and it struck us that a great dissertation idea would be to actually test this. What you'd need is a large-ish area with many handaxe assemblages recovered using modern excavation techniques for which a baseline chronology is known - some place like the Middle Awash River Basin, maybe. Then, you explicitly define what gets considered a handaxe, and you apply it to all these assemblages (e.g., at minimum, any piece with removals from both surfaces - this is obviously a minimalist definition, but it's given here as an example). Then, you define a way to measure symmetry and establish a baseline for what is considered 'symmetrical' or whether you're looking at symmetry as a continuous variable (ideally, you do both in order to fend off eventual critiques). Then, you get a sense of raw material constraints, site function and reduction intensity for each assemblage, in order to see whether or not any of these is a recurrent conditioner of handaxe morphology, and to factor them out if they do. In particular, you need some controls such as an evaluation of how inherently 'symmetrical' cobbles or flakes used to make handaxes are at various locales, and whether or not this is correlated to symmetry in various assemblages across the study area. Lastly, you measure symmetry on these handaxe assemblages and then, you look at trends over time. Then, you look at various measures: mean vs. median symmetry, coefficient of variation, spread of values, whether or not certain levels of symmetry are only reached after some point in time; the list goes on and on. The point is, we need to actually demonstrate this at the very least at a regional level before we can even consider taking 'increased handaxe symmetry' as the starting point for any subsequent analysis. So there - if you're a graduate student looking for a project, feel free to take this one. I can all but guarantee you that the resulting papers, whether they demonstrated one or the other conclusion, would become ridiculously highly cited.

I think that what we now know about technology (especially earlier technologies like the the Oldowan) would set the null hypothesis here as being that we shouldn't expect increasing symmetry or standardization over time. In other words, high degrees of symmetry can be present from the beginning of the Acheulean and low symmetry can occur in its latest phases. If you look at the Oldowan, the data clearly indicate that people didn't start by knocking off one flake, then a few thousand years realizing that they could knock off another one, and then another one yet more thousand years later. Quite the opposite, it seems that by the time people start regularly working stone, they get it pretty well: they know how to knock off flakes in succession, they realize that different materials flake better than other, going to some effort to get the better stuff (e.g., Stout et al. 2010). My impression is that the same is likely to be applicable to handaxe technology: once people start flaking cobbles bifacially, they also get it: they realize that you can knock flakes off both surfaces, often using one removal as the starting point for removing another one. And if they understand this, then making an object symmetrical as a result is also implicit - the question becomes why symmetry in certain case and not in others, and why this is the case

So, to go back to Lam's argument, my take on it is not so much that it's wrong (it might end up being right) that I think that we don't have nearly the archaeological resolution we need to objectively discuss the issues she tackles, especially those linked to the question of increasing handaxe symmetry over time, let alone the interpretation of such a pattern. Only when the baseline archaeological work has been conducted, can we really hope to usefully revisit the question.

Some earlier posts on the Acheulean and handaxes:

Plus-sized in the Pleistocene

Two sides to every biface

I say Acheulean, you say Acheulian

References and some suggested reading:

Machin, A. 2009. The role of the individual agent in Acheulean biface variability: A multi-factorial model. Journal of Social Archaeology 9: 35-58.

McPherron, S.P. 2000. Handaxes as a Measure of the Mental Capabilities of Early Hominids. Journal of Archaeological Science 27:655-663.

Monnier, G. 2006. The Lower/Middle Paleolithic Periodization in Western Europe: An Evaluation. Current Anthropology 47:709-744.

Nowell, A., and M.L. Chang. 2009. The Case Against Sexual Selection as an Explanation of Handaxe Morphology. PaleoAnthropology 2009: 77-88.

Stout, D., S. Semaw, M.J. Rogers, and D. Cauche. 2010. Technological variation in the earliest Oldowan from Gona, Afar, Ethiopia. Journal of Human Evolution 58: 474-491.


terryt said...

Surely if the axes were used as 'trade' they should have moved some distance from where the original rock was found. With increasing development of petrological analysis it should be possible to at least gain some idea of distances 'traded'.

Julien Riel-Salvatore said...

Terry -
that's certainly a possibility, though it would depend on the size of the social network over which these things were exchanged, and the amount of 'trade' taking place. Unless of course, they got traded back and forth between parties, in which case distance to source might not be a good indicator of the amount, intensity or even nature of this form of commodity exchange.


Torwen said...

Didn't Steven Mithen write something about handaxes and symmetry? It was however, more about sexual selection than money ... but then, on the other hand, there probably isn't much difference :)

Julien Riel-Salvatore said...

Torwen -
Thanks for your comment. Mithen did indeed write something about some especially symmetrical handaxes serving as a type of 'costly signaling' to get mates. You're definitely right that his argument was about as convincing as this one, for many of the same reasons.

Nowell and Chang wrote a very through debunking of his argument, in a paper that is available for free in the journal PaleoAnthropology (The Case Against Sexual Selection as an Explanation of Handaxe Morphology). You should definitely check it out, if the issue interests you.