How monolithic was the Acheulean?

I'm taking some notes on change and stasis during the Acheulean, and they're not entirely complete, but in the interest of clearing my desktop I'm going to start posting them in sections.

We can start with some epitaphs on the era as a whole:

Standard textbook knowledge informs us that the Acheulean was remarkably the same throughout its geographic distribution. For example, African handaxes are supposed to be very similar to European and Indian handaxes. It is also well known that handaxes come in a variety of shapes. However, there seemed to be no clear correlation between the various shapes and the geographic regions in which they were found, giving the Acheulean a markedly monotonous flavor (Wynn and Tierson 1990:73).
Currently, two perspectives dominate the interpretation of these tools. The first is that they result from "mental templates" held by the knappers and reflect shared cultural norms. The second is that their shapes were an unintended result of a knapping procedure and the use life of the artifact and have no implications for culture or cognition (Wynn 2004:674).

Regional differences

One argument favors cultural continuity as an explanation for handaxe persistence: there appear to be some regional differentiation of modal handaxe form in the later Acheulean. Wynn and Tierson (1990) find that handaxes from the later Acheulean of Israel had an average form that was wider than those from Africa, England, or India. Comparable differences in form did not distinguish these other regions from each other. Wynn and Tierson (1990) concluded that cultural transmission was the most reasonable explanation for this interregional difference. The difference in form was consistent across different raw materials, and they considered raw material a confounding variable contributing to variation, rather than an explanation for the interregional difference. They could not eliminate the possibility that the difference reflected temporal change -- since most of the sites were effectively undated.

Regional differences in form are not a problem to explain under the noncontinuous account. As handaxes were independently invented in several different traditions, there is no reason to think they should be exactly alike. Within the functional constraints upon them, there was evidently substantial room for variation -- as indicated by the variation of form within regional samples, and within individual sites. Undoubtedly, there was substantial variation in form among handaxes crafted by individual makers.

What may be surprising is that there was not more interregional variation in form. This uniformity may appear as evidence for cultural or genetic transmission. But it may equally represent the lack of transmission. If different local groups or regional populations did not share a long continuous genetic or cultural chain of handaxe-making instructions, then they would have effectively explored the functional space of bifaces repeatedly in each region. This exploration would have introduced substantial temporal differences between levels at single sites. Different regional samples would each represent samples of the same, broad, statistical population of handaxe variants.

And of course, if the function of handaxes was really to serve as a core for the production of flakes (discussed here), then there is another good reason why regions might vary in handaxe width in particular -- some local regions may have had more intensive raw material utilization than others, regardless of the raw material type. Where exposures were common, people would have been less likely to use the same cores as intensively. Where cores were rapidly buried, they would have been less likely to reuse them to full depletion. This is essentially the explanation favored by McPherron (2000) for the same pattern of observations: the differences may be explained by a combination of raw material size and reduction intensity. In support of this idea, he notes that Gowlett and Crompton (1994) show that handaxe width is allometric against length; smaller and more intensively flaked handaxes tend to be relatively shorter -- and hence, relatively wider compared to their lengths.

Standardization and mental categories

McNabb et al. (2004) examined assemblages of bifaces from ESA sites in southern Africa. They found that standardization and symmetry among the bifaces were "not a high priority". In contrast to the hypothesis that handaxe form is a mental template imposed on raw material, they concluded that there was little evidence for standardization, beyond the size and general functional characteristics of the bifaces.

From this lack of standardization, McNabb et al. (2004) speculate that the Acheulean people did not learn to make tools by internalizing a strict concept of form, and did not use tool shape itself to convey information.

Rather than being a tightly conceived and culturally sanctioned outline form acquired and maintained through social learning, the shape of a large cutting tool was a variable idea in the mind of the knapper. The specific form of the tool depended on individual ability, the perceived constraints imposed by raw-material shape, function, time, and social factors, all of which could change with time, place, and circumstances (McNabb et al. 2004:667).

McNabb et al. (2004) proceed to argue for the idea that these tools were maintained as individualized memic constructs, meaning that the idea of making the tools was socially learned, but the final shape of the tools itself was not the object of that learning. Certain steps in tool production may have been conceptually standardized, meaning that the toolmaker learned certain tricks through observation and carried those out in a standardized fashion, but did not standardize the end product.

Standardization is not necessary to the physical function of a stone tool. The presence of standardization implies a non-physical function; either communicative or normative. The claim that Acheulean bifaces were extensively standardized to a common template is a claim for a nonphysical role -- standardization cannot be explained in the absence of such a function.

So a claim that Acheulean bifaces are not standardized is significant in that it denies a nonphysical (i.e., symbolic or communicative) role for these tools.

McPherron (2000) summarizes much of the 1990's debate about regional and temporal differences in biface manufactures, and draws out the conclusion of functional rather than mental uniformity in two parts:

It still must be questioned, however, whether these data actually indicate "mathematical transformations" or "mental templates" as Gowlett suggested. Is it really surprising, for instance, that length and width converge on zero? The fact is that in a reduction technology such as lithics, it can hardly do otherwise.... The only way it could be otherwise would be if the length or width removal rate changed at some point in the reduction sequence. If this were the case, then length and width would not be highly correlated, and Gowlett would not be able to argue for a high level of standardization (McPherron 2000:662, referring to Gowlett 1984).
Moreover, the very distinct possibility that handaxes were reworked and that shape changed as a result, challenges the basic underlying assumption of most studies of handaxe shape: namely, that a particular shape is the desired end-product of the bifacial reduction sequence. This problem exists regardless of whether handaxes were cores or tools or both. Either way, handaxe shapes represent stages in a continuous reduction process. Given the data presented and reviewed here, it can be concluded that this reduction process was remarkably similar in various parts of the Old World and at various times in the Middle and Late Pleistocene, suggesting that if there were a mental template, it was the same mental template (McPherron 2000:662-663).

In contrast, Wynn (2002) suggests that bifaces -- at least, those produced late in the Acheulean -- were products of people who possessed mental categories for them. Wynn (2002) outlines and describes evidence for attention to three aspects of symmetry in stone tools, beginning with congruency and proceeding to three dimensional symmetry and finally the deliberate breaking of symmetry.

These handaxes were almost certainly categories, and categories are abstract, multi-modal, and rely on associative memory. As such they reside in declarative memory, which "requires associative links between several types of information that are stored in different areas" (Ungerleider 1995, p. 773). These hominids could manipulate perspectives and spatial quantity, produce congruent symmetries, and even distort these principles to achieve striking visual effects (Wynn 2002:397).

I am ambivalent about whether and to what degree such artefacts may have had a social role beyond their utilitarian function. I think it unlikely that hominids who could deliberately alter symmetry to achieve an effect would not also apply this mastery upon some other artifact. If these modes of manufacture were learned socially, and if they could vary arbitrarily from a single template, then there should have been not only individual variations (which have a more-or-less constant distribution across space) but also regional and local variations (which would have a discontinuous distribution across space). Yet there is precious little evidence for such interregional variation -- or "style" -- until the MSA and Middle Paleolithic. Even there, it is not obvious that the regional differences are stylistic rather than functional. There are suggestions that other artifacts expressing "categories" did exist in the later Acheulean, including possibly carved sculptures like Tan Tan and Berekhat Ram, and deliberately incised lines like the Tata artifact. More of these would substantiate the case better. As it is, these are credible as products of individuals, but do not document a communicative aspect to artifact production or a tradition of such social and mental categories.

On the other hand, the null hypothesis of "no mental templates" must surely apply with more force to the earlier part of the Acheulean, and less to the later part. Wynn's (2002) argument may well apply with force to the later Acheulean, the period he examines, while not being true of earlier humans. In this case, the evidences for manipulating symmetries in artifacts may substantiate an increasing technical skill and "concepts" in some sense. The communication of a concept through the use of external objects would indeed represent an advance in human mental interactions and social learning. In this context, a reading of Wynn's (2002) response to discussants on his paper is worthwhile. In particular, he makes a clear distinction between earlier and later Acheulean in terms of the recognition and manipulation of symmetry.

References:

Gowlett JAJ, Crompton RH. 1994. Kariandusi: Acheulean morphology and the question of allometry. Afr Archaeol Rev 12:3-42.

Sheppard PJ, Kleindienst MR. 1996. Technological change in the Earlier and Middle Stone Age of Kalambo Falls (Zambia). Afr Archaeol Rev 13:171-196. DOI link

McNabb J, Binyon F, Hazelwood L. 2004. The large cutting tools from the South African Acheulean and the question of social traditions. Curr Anthropol 45:653-677.

McBrearty S. 2003. Patterns of technological change at the origin of Homo sapiens. Before Farming 3:1-6.

Wynn T, Tierson F. 1990. Regional comparison of the shapes of later Acheulean handaxes. Am Anthropol 92:73-84.

McPherron S. 2000. Handaxes as a measure of the mental capabilities of early hominids. J Archaeol Sci 27:655-663. DOI link

Wynn T. 2004. Comment on "The large cutting tools from the South African Acheulean and the question of social traditions". Curr Anthropol 45:672-673.

Wynn T. 2002. Archaeology and cognitive evolution. Behav Brain Sci 25:389-438.