The Center for the Advanced Study of Hominid Paleobiology [CASHP]
To understand the importance of Palaeolithic stone tools in relation to the Fossil Record, the Bradshaw Foundation spoke with Cassandra Turcotte of the Center for the Advanced Study of Hominid Paleobiology [CASHP] of George Washington University. What could the study of the Lower and Middle Palaeolithic lithic technologies - the earliest instances of innovation - reveal about the cognitive and symbolic processes involved? Are stone tools the first signs of creative behaviour?
Cassandra M. Turcotte - The Center for the Advanced Study of Hominid Paleobiology (CASHP)
Oldowan Stone Tools
First coined by Louis Leakey in 1936, the Oldowan is a term used to describe the earliest evidences of the human fossil record. Beginning 2.5 million years ago and restricted to Africa (de la Torre, 2011), the Oldowan industry can still be found in the form of similar flake tools in hunter-gatherer societies across the world today, even if it has been largely replaced by more advanced technologies. Leakey named this archaeological culture after the first area in which he documented it - the now-famous site of Olduvai Gorge in Tanzania, Africa (Schick and Toth, 2006). His wife, Mary Leakey, published the first comprehensive work on the pair's finds at Olduvai in her book Olduvai Gorge Volume 3: Excavations in Beds I and II, 1960-1963 (Schick and Toth, 2006). This work is notable because it recognized the first instances of tool-making in human history, separated the Oldowan from the later Acheulean, and gave description to these earliest artifacts.
The Oldowan represents the first instances of technological innovation in human history, wherein our ancestors first began to enhance their biological abilities with the manufacture of stone tools. This speaks to an important milestone in the evolution of our ancestors. Tool production and use is thought to be intimately linked to, if not the instigator of, major changes in cognitive development; geographic ranges; and morphological features like body and brain size (de la Torre, 2011; Schick and Toth, 2006). Although the exact nature of these relationships remains contested, better understanding of these issues will inform our state of knowledge on subjects from the evolution of human cognitive sophistication to the timing of our genus' first use of fire or hunting.
This technocomplex is characterized by a limited variety of simple artifacts, such as flakes; hammerstones; and cores with very little, if any, evidence of retouch. Hammerstones represent the usually fat, round stone one holds when percussing the stone of interest. Hitting this block at the right angle with high-impact will produce a thin, flat flake patterned with conchoidal fracture and a bulb of percussion. What remains of the block used to produce the flake is called a core (Kimura, 2002; Schick and Toth, 2006). Flakes can be categorized in a number of ways (i.e., chopper or scraper) depending on their morphology but all are distinct from natural stones from the artifacts of their manufacture (fracture lines, bulbs of percussion). The classification system of flake technology has itself changed much over the years, owing to debate between the Leakeys; Dr. Nicholas; and renowned French Acheulean archaeologist Dr. Francois Bordes (de la Torre, 2011; Kimura, 2002; Schick and Toth, 2006). In comparison to the Acheulean technologies, the Oldowan may seem relatively simple. This does not mean it represents anything less important. Rather, Oldowan technologies illustrate a graded development of stone tool complexity in the archaeological record.
The first instances of Oldowan tool technology crop up in Eastern Africa around 2.5 million years ago, following a period of global climate cooling and drying. As a result, African geography had changed quite a bit, with grasslands becoming predominant (Kimura, 2002; Schick and Toth, 2006; Stout et al., 2005). Interesting changes were also happening to the several branches of the human lineage alive at that time, with the advent of robust australopithecines and our own genus, Homo. Thus, the candidates for the inventors of the Oldowan are many. There are the gracile australopithecines, Australopithecus afarensis (3-2.2 myr) and Australopithecus garhi (2.5 myr) as well as the robust Paranthropus aethiopicus (2.5 myr), Paranthropus boisei (2.3-1.2 myr), and Paranthropus robustus (2-1 myr). This time period is also recognizable for the beginning and diversification of our genus, with Homo habilis (2-1.6 myr); Homo rudolphensis (2.4-1.7 myr) and Homo ergaster/Homo erectus (1.8- <1 myr) existing in temporal proximity to each other (Schick and Toth, 2006).
All but Au. africanus were dated to the same time period as nearby Oldowan sites (Schick and Toth, 2006). Unfortunately, few fossil remains are directly associated with Oldowan technology in the archaeological record. In one instance of this at the Olduvai Gorge site FLK, both Paranthropus boisei and Homo habilis were found in direct association with stone tools. Indeed, many mammals were found in direct association with the Oldowan technology (Schick and Toth, 2006). A specimen of early Homo, STS 53 from South Africa, exhibited a cut-mark that could have been from a stone tool, although whether early Homo made the cut remains yet another uncertainty (Schick and Toth, 2006). Even instances of direct association can be difficult to decipher and we must seek out other sorts of evidence.
Initially, having worked at FLK, Mary Leakey proposed that Homo habilis was responsible for the tools rather than Paranthropus boisei (Schick and Toth, 2006). This supports the timeline for relating stone tool production the increase in brain size, and remains a popular hypothesis in current paleoanthropology (Schick and Toth, 2006). Other researchers, like Susman (1991), suggest that the robust australopithecines were more likely the producers of the Oldowan out of necessity. Very simply, the robust australopithecines needed to process very tough plant resources, a task Susman (1991) claims would have required tools. Susman (1991) supports this idea with the assertion that Paranthropus' hand morphology was adapted for precision grasping. Given the contemporaneous nature of the hominid species at that time, it's possible that any one up to all of them had some part to play in the shaping of the Oldowan. In spite of that possibility, it's known that only one genus survived past 1 million years ago: Homo.
In addition to who could have made it, the question of the Oldowan's functionality also remains largely unknown. This problem contributes to a larger debate about the nature of early human meat acquisition - was it hunting, or was it scavenging? The precise use of the tools can't, of course, be determined, but experimental functional studies have gone a long way in the description of functional features (Schick and Toth, 2006). This boils down to whether hominids had primary access (hunting) or secondary access (scavenging) to carcasses and deals with the requirements of each scenario (Dominguez-Rodrigo et al., 2004). Primary access gives predators a better selection of most nutritive meat, for example. Schick and Toth (2006) argue that this mode of meat acquisition would not necessarily require the kinds of processing that secondary access would, wherein the marrow inside bone would represent the best-value resource (see also Dominguez-Rodrigo et al., 2004). Therefore, bones with percussive damage or fracturing would more likely be attributed to secondary access. This particular debate has not yet been resolved.
Contributing to this problem are speculations that our cousins, the chimpanzees, could have produced these materials as well. Once thought to have extremely primitive cognitive and technological abilities, chimpanzees are now observed to make and use tools for a number of tasks (Goodall, 1986; Schoning et al., 2008; Schick and Toth, 2006). In chimpanzee tool making, however, their chosen materials are often organic, leading to decreasing likelihood of preservation (Toth and Schick, 2009). These tools include items such as long, stripped sticks used for termite fishing (Schoning et al., 2008). Additionally, chimpanzees also use stone tools, often in the form of hammers and anvils for the cracking of nuts (Toth and Schick, 2009). While some researchers argue that the stone artifacts from such activity are comparable to Oldowan lithics, others claim the battered, fractured stones don't really represent the type of careful, thought-out knapping exhibited by the Oldowan tools (Toth and Schick, 2009). In experimental studies, African apes like bonobos have been trained to successfully produce Oldowan-like tools, but less skillfully (Schick and Toth, 2006). The possibility of chimpanzee toolmakers, however, brings up another controversy - that of the Pre-Oldowan.
The Pre-Oldowan is a term given to tools older than 2 million years at sites like Gona, Ethiopia and West Turkana, Kenya, which seem to exhibit less skill than we expect from the traditional Oldowan (Schick and Toth, 2006). It's true that these sites seem to exhibit fewer instances of retouching, which becomes more prevalent after 2 myr at Olduvai and East Turkana (Schick and Toth, 2006). Recent studies have shown, however, that even among the oldest sites flakes do indicate high levels of skill. For example, at Gona, Ethiopia, material dated to 2.5-2.6 myr represented skillfully flaked lava cobbles (Schick and Toth, 2006; Semaw, 2000). Gona and its associated site Bouri also showed evidence of raw material selectivity, with a preference for felsic volcanic rocks as opposed to the mafic basalt common to Olduvai and Koobi Fora. This indicates a clear hominid preference for fine-grained and phenocryst-poor rocks more suitable to flaking as well as the ability to plan ahead for future tool production (Stout et al., 2005). Evidence suggests that skillful flaking and forethought were components of human tool production even as early as 2.5 million years ago, quite contrary to the concept of the Pre-Oldowan, although this conclusion is still in contention.
It's hard to know much about a world and its inhabitants so far into the past, but we can make tentative steps in this direction using archaeological material. In the case of human behavioral evolution, the first evidence that we have come in the form of simple stone tools that we've categorized as the Oldowan. Simple flakes, cores and hammerstones that could be mistaken for natural to an untrained eye give us insight into lives and needs of our ancestors. From hunting/scavenging behavior to the advancement of cognition, these tools provide an enigmatic window into the past. These debates are still ongoing, showing quite clearly the contentious nature of making functional conclusions about artifacts we don't completely understand. There are plenty of things still unknown about the Oldowan, even up to who first made or used them, but endeavoring to discover more about these tools contextualize later technocomplexes and help inform researchers in their debates about cognition, behavior, and the evolution of human technological innovation.
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