One study reported at the meetings brought to mind a growing literature on the sophistication of Pliocene archaeological assemblages, grouped as "Oldowan" or "pre-Oldowan." Most Oldowan tools lack a standardized form, and the assemblages are dominated by flakes, core tools with one sharp edge or point, and unmodified manuports or hammerstones. The lack of standardized tools (such as handaxes) lead easily to the conclusion that Oldowan technical assemblages are simple, so that anyone could make one who could chip rock.
But a number of recent sources illustrate that this perception isn't accurate. The Oldowan encompasses a variation of manufacturing complexity and other elements, but cannot be said to be merely rocks that have been carried or bashed together. The most interesting studies have examined the issue of raw material exploitation and the actual processes used to reduce stone into useful tools.
David Braun gave a presentation that relates to this topic at the 2005 Paleoanthropology Society meetings. In an analysis of the lithic remains at the Kanjera South site (Kenya), the group found that the intensity of the reduction sequence varied with source material.
Kanjera South, dating to around 2.2 million years, preserves one of the largest early records of material culture. According to Plummer et al. (2001:810):
Hominins at Kanjera South utilized a wider variety of lithic raw materials than found at most Oldowan sites, some of which (chert, quartz, quartzite) must have been transported from outside the immediate vicinity of the deposits since they are not present in the local clast population.
In the study by Braun et al. (2005), fine-grained quartzite, which had a nearest source outcrop a long distance away from the site, was reduced more intensively than locally available rock. This reduction involved more flakes taken per core, and occasional retouch. They hypothesized that this difference was due to the hardness of the quartzite and its ability to hold an edge, which makes tools made on quartzite potentially more useful. The hominids apparently recognized these qualities in the raw materials and exploited the quartzite. We can probably infer that the transport distance was a result of this recognition as well.
Stout and colleagues (2005) report on the use of raw materials at Gona, which is at present the earliest site at which stone tools are found, dating to around 2.6 million years. This study sampled unmodified stone taken from conglomerates that represent natural accumulations. If stone were taken merely from local sources without selectivity, the modified stone assemblages from the site would be expected to match these conglomerates. As described by Stout et al. (2005:366-367), the past understanding of Oldowan toolmakers has suggested that they may not have exhibited a clear understanding of the technical qualities of their raw materials:
At Koobi Fora, the high frequency of basalt in local conglomerates (i.e. ancient stream channels) is closely mirrored by its predominance in the artifact assemblages (Toth, 1985; Schick, 1987; Isaac et al., 1997). Although quartz, chert and glassy volcanics are "reasonably easily available" in the conglomerates, these material types do not appear to have been specifically selected for (Isaac et al., 1997:268).
This paper gives an excellent review of the history of raw material choice. In brief, the literature review indicates that early toolmakers at Koobi Fora may have exercised some degree of selectivity by avoiding certain kinds of stone (vesicular lavas and weathered cobbles). By Olduvai Bed II (after 1.7 million years ago), some toolmakers were clearly going out of their way to acquire certain stone materials:
The increased use of chert at Olduvai around 1.65 Myr was clearly occasioned by the temporary exposure of rich sources of this material by the retreating waters of the paleo-lake (Hay 1976). Hominid toolmakers at this time readily appreciated the superior flaking properties of chert, leading to the formation of the earliest known special-purpose quarry site at MNK CFS (Stiles et al. 1974; Stiles 1998) (Stout et al. 2005:367).
So when did this technical knowledge really originate? Was it a skill that developed gradually over the million years between Gona and Olduvai Bed II?
Stout and colleagues find that the materials used for tools at Gona do not match the natural cobbles that were avaiable in a number of respects. In essence, the hominids ignored many kinds of stone that had fracture patterns or other properties that made them less suitable as raw materials. They (2005:368) state the conclusion most clearly at the end of their introduction:
The strong pattern of raw material selection seen at Gona demonstrates that low levels of selectivity are not universal in the Oldowan. The fact that the assemblages from Gona are the oldest known in the world also argues against an overarching temporal trend toward increasing selectivity within the Oldowan.
The flaking skill of early hominids is the subject of a paper by Roche and colleagues (1999) in Science. At the two localities of Lokalalei 1 and 2C, both dating to 2.34 million years ago on the west shore of Lake Turkana, this study accomplished refits of stone flakes and cores to directly inspect the reduction sequence. They found that this sequence was quite complicated in many of the instances of manufacture at the two localities:
At LA2C, the dominant reduction sequence consists of these more reduced cores. Unidirectional or multidirectional removals are flaked on a single debitage surface, from natural or prepared platforms. This knapping system allows the production of a long series of removals without changing the volumetric structure of the core. The repeated application by the knappers of the same technical principles to a whole series of cores, and during the reduction of each core, indicates an elaborate debitage scheme, implying motor precision and coordination. These principles include an appreciation of the quality of the collected raw materials, a judicious exploitation of the natural morphology of the blocks and the maintenance of adequate flaking angles during the entire debitage sequence. These show that the notion of production was already assimilated by a group of hominids in this particular area. This notion is integrated within a real debitage strategy, here well-mastered and unprecedented for this time period (Roche et al. 1999:59).
Upon this description and analysis of the debitage, the study bases the following conclusion:
Overall simplicity and similarities between assemblages are the two main arguments recently put forward to substantiate a technological stasis hypothesis between the 2.6 and 1.6 Myr time periods, and to merge the related assemblages into a single vast 'Oldowan' technocomplex. The stasis hypothesis cannot hold out against the detailed technological analysis of the LA2C lithic assemblage. There can be no doubt about the elaborate character of the LA2C debitage schemes, which are far more sophisticated than at any other Pliocene site (Roche et al. 1999:59).
In total, these studies attest to the technological expertise of some early toolmakers. It is perhaps important to remember that the archaeological record should be expected to reflect an average technical competence much less than that possible (or possibly even typical) of early hominids. For example, every instance of stone flaking by an expert toolmaker certainly was preceded by novice flaking by the same individual earlier in his life. Considering the early mortality evidenced by australopithecine (and early human) remains, many potential toolmakers must have died before reaching proficiency. And toolmaking expertise was probably not uniformly distributed among social groups, so that some individuals had the opportunity to learn by observation some relatively complex reduction sequences and material properties, while others would have had to acquire the same knowledge by long trial and error, if at all.
In this framework, later changes in the archaeological record may reflect social and life history changes as much as ecological changes or brain evolution. Toolmaking intensifies later in the Oldowan, raw material selectivity increases, and some standard forms and more technically sophisticated artifacts, such as bifaces, routinely occur. The increased mental complexity of Pleistocene hominids may be a cause, but the behavioral changes have no obvious anatomical, life history, or other correlate. The apparent sophistication of the earliest toolmakers argue against the hypothesis that the later Oldowan represents a fundamentally more intelligent hominid species, with specialized adaptations to tool manufacture lacking in earlier hominids. Instead, I would suggest that later Oldowan hominids had on average a greater retention of cultural knowledge as a function of more stable groups and a longer life history than australopithecines. This shift might or might not have been accompanied by an increase in the capacity to learn, as might be evidenced by a greater length of the juvenile growth period.
From a conceptual perspective, there is necessarily a real limit on the standardization that is possible within any "technocomplex," and particularly one that spans a million years or longer. The kind of information that is ultimately transmissible (either horizontally or vertically) among hominids over this extreme time period is of the most rarified form imaginable. A model of early archaeological assemblages that incorporated the probable manner and form of information transfer among groups (along with their global demography) would predict both a global lack of complexity and a great extent of variability within that simple context. The evidence of technical skills therefore may inform directly about the demography of groups and their relationships with each other. The extent to which such variability may be consistent with cultural diffentiation among groups in other primate species (such as chimpanzees) I take to be a testable hypothesis.
Most references within the featured articles below:
Plummer T, Ferraro J, Ditchfield P, Bishop L, Potts R. 2001. Late Pliocene Oldowan excavations at Kanjera South, Kenya. Antiquity 75:809-810.
Roche H, Delagnes A, Burgal JP, Feibel C, Kibunjia M, Mourre V, Texler PJ. 1999. Early hominid stone tool production and technical skill 2.34 Myr ago in West Turkana, Kenya. Science 399:57-60.
Stout D, Quade J, Semaw S, Rogers MJ, Levin NE. 2005. Raw material selectivity of the earliest stone toolmakers at Gona, Afar, Ethiopia. J Hum Evol 48:365-380.