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)
Acheulean Stone Tools
The Acheulean is a technological tradition characterized by an incredibly long history in the human cultural record across unprecedented geographical spans. First described in the 19th century by Gabriel de Mortillet and named for the French town of Saint-Acheul, the Acheulean uniquely includes the first appearance of the bifacial tool known as the handaxe (Wood, 2011). Two perspectives paint this technocomplex as either a great leap in human cognitive abilities and technological prowess or a long period of technological stagnation.
Early Acheulean handaxe from Sterkfontein Cave
The Acheulean industrial complex consists of flakes, retouched flakes and, most notably, bifacial tools (Clark, 1994). The earliest sites containing Acheulean technology come from East Africa up to 1.6 myr and terminate 200 to 100 kyr, making this an incredibly long-lasting technological industry (Clark, 1994). For a long time, the oldest known occurrence of the Acheulean was from Olduvai Gorge at the EF-HR site dated to 1.4 myr. This site had no associated human remains (Clark, 1994). This changed in 1992, when Asfaw et al. (1992) published their report on discoveries made at Konso-Gardula in the southern Main Ethiopian Rift (Clark, 1994). With Acheulean artifact-rich sediments spanning 1.3-1.9 million years, this discovery pushed the first appearance datum of this technological tradition up to almost half a million years and tied the tradition to Homo erectus, thanks to hominid dentition and a mandible also discovered at the site (Asfaw et al., 1992).
Early acheulean biface from Gona, Ethiopia
Other early occurrences of the Acheulean include the appearance of handaxes and cleavers at Sterkfontein in association with calvaria from Homo habilis dated to 1.6 myr and a few sites in northern Africa, including Sidi Abderrahman in Casablanca and Tighenif in Algeria, both from .7 myr. The Acheulean even makes it out of Africa into the Jordan Valley site of 'Ubeidiya by 1-1.4 myr (Clark, 1994). In many of these sites, including at 'Ubeidiya and Konso-Gardula, the link to Homo erectus is clear and this species is now associated as the maker and user of the early Acheulean technologies.
Map of expanse of Acheulean
The geographic expanse of the Acheulean includes Africa, the Near East, India and parts of Europe, although it does not penetrate into Asia. These distributions have given rise to the notion that the Acheulean (or 'Mode 2') technologies arose in Africa and were brought into Europe and on to India via the dispersal of hominins, particularly the Homo erectus with which the early Acheulean is associated (Lycett and von Cramon-Taubadel, 2007). Indeed, this conclusion finds general support from chronological data and experimental hypothesis-testing conducted by Lycett and von Cramon-Taubadel (2007), in which they modeled dispersal pattens in conjunction with transmission of Acheulean technology. They reiterate that Acheulean technologies developed in Africa and dispersed from that center of origin into Europe, the Middle East and India with repeated bottlenecking events.
Interestingly, the Acheulean failed to permanently penetrate much of Asia and the boundary dividing the parts of Asia with and without handaxes was termed the 'Movius' line. The archaeologist for which the line was named, Movius, determined that this was because Asia was a continent of cultural stagnation. Other researchers have variably attributed the absence to availability of organic tools (i.e., bamboo shoots) or the continued use of Mode 1 technologies in eastern Asia while Europe, Africa and the Asian subcontinent moved on to the Acheulean (Lycett and Bae, 2010). Eventually, Acheulean-type technologies were discovered in eastern Asia, although always at low frequencies. Such sites include the Hantan River Basin in Korea and in the Bakosa Valley in Indonesia, where handaxes are found at higher frequencies but mostly less than 5 percent of the assemblage. Lycett and Bae (2010) propose five explanations for the possible low frequency, including the possibility that human dispersal into eastern Asia came before the innovation of the Acheulean. Evidence of hominins in eastern Asia begins at sites like Yuanmou in southern China, Majuanggou in northern China and Sangiran in Indonesia. Dates for these sites, though controversial, go up to 1.8 myr, which means that hominins might have been there before the hominins in Africa first produced Acheulean-type tools (Lycett and Bae, 2010). There are also raw material constraints, the possibility of geographical and topographical barriers, the issue of bamboo availability and questions of social transmission. In short, there are many reasons why the Acheulean never made a big splash in eastern Asia, although it certainly made it to the rest of the Old World and stayed there for over a million years.
An Acheulean handaxe, Haute-Garonne France
The Acheulean itself is an important development in the history of human evolution, as this more advanced form of stone tool production purportedly indicates a leap forward in cognitive abilities. The handaxes themselves were used to process game and their production requires both long term planning, forethought, adaptability and understanding of the material to achieve the desired end result (Goren-Inbar, 2011). The handaxe is a raw material upon which a hominin has imposed a formed, a '[reflection of] shared mental templates' (McPherron, 1999). It is argued that variations through time in terms of morphology may then be interpreted as changes in cognition, although researchers like McPherron (2011) contend that shape actually only reflects more basic factors like raw material or reduction intensity (see also Archer and Braun, 2009). Indeed, Lycett and Gowlett (2008) suggest that the uniformity in the Acheulean Bauplan over such large expanses of geography an time indicate that the technology was under the pressure of strong functional constraints or, variably, cultural influence. McNabb et al.'s (2004) study questioned whether the Acheulean actually required social learning and found that 'cultural templates did not dictate the specific appearance of large cutting tools' at their sample site. Other archaeologists insist that the Acheulean signals cognitive advancement and stylistic variation, rather than mechanical constraint.
Ovate acuminate handaxe from the later Acheulean
For example, in Goren-Inbar's (2011) study, the author analyzed an ethnographic study of flint-knapping populations of the Irian Jaya, who produced bifaces from volcanic rocks. The process of production of bifaces was observed to require long-term memory, spatial or procedural cognition, advanced planning, and procedural 'know-how' or social cognition. Other research takes a neural approach, contending that higher order cognitive function is tied to motor action and that these processes must be in synchrony in order to make an Acheulean tool (Stout, 2011). According to Wu et al. (2011), Homo erectus endocasts suggest that these species may have had selective enlargement of neural areas relevant to tool-making cognitive processes. Thus, the Acheulean actually could signal both innovations in social cognition and technological creativity, although this conclusion is currently under debate.
Late Acheulean handaxe from Kathu Pan, South Africa
Whether or not the morphology of the Acheulean tradition was determined by material or mental template, there's no denying that the lives of hominins during those million and a half years was anything but stagnant. This interval saw the rise of genus Homo and the decline of the australopithecines, periods of climate change and environmental variability, dispersals within and out of Africa, and numerous behavioral adaptations. One of the most famous of latter include advances in foraging strategies. That is, it's during this period that we first see definitive evidences of hunting and fire.
According to Clark (1994), evidence for use of fire, thought postulated by 1 myr, is only made definitive by .5 myr, with the discovery of several sites, including burnt bone at Verteszoellos; charcoal, burnt bone, ash and burned stone at Zhoukoudian; and other materials at sites like Terra Amata and Gesher Benot Ya'aqov . Reddened patches from Koobi Fora dated to 1.6 myr likely represent repeatedly used hearths, according to thermal and paleomagnetic data (Wrangham et al., 1999). Brain and Sillen (1988) also report burnt bones from sediments containing hominin fossils from 1-1.5 myr. Refining the dates for the appearance of fire is important because cooking has both energetic importance in human evolutionary history as well as significant implications for social structure. According to Wrangham et al (1999), cooking food is responsible for the social system we know today as pair-bonding within a multi-male, multi-female group. Thus, it's clear that the advent of the use of fire could have had a significant effect on hominin social patterns and, in turn, diet.
Raw material types used in Acheulean handaxes
And, although still in dispute, it's likely that hominins' skill in hunting greatly improved in this period. Acheulean tools have been found in association with butchered elephant and hippopotamus skeletons, for example, suggesting elephant hunting at the site of Torralba and Ambrona, although this is disputed (Clark, 1994). Speth (1989), for example, contends that early hominins ate less meat than we give them credit for, positing that meat's low energy value during times of stress made it an inefficient fallback food. Australopithecines most likely subsisted on a diet composed primarily of plant material, which would have largely been energy-poor resources, as evidenced by isotope data and the diets of modern subtropical foragers. More energy-rich foods like meat start showing up in the form of butchered bones during the Oldowan about 2.3 myr, which is followed by a reduction in hominin tooth size after 2 myr. Homo erectus, the makers of the Acheulean, exhibit an increase in body mass, reduction in tooth size and enamel thickness, and concomitant increase in brain size suggesting an increase of energy expenditure by a margin of 80-85% over australopithecines (Wrangham et al., 1999). This strongly suggests that early hominins made at least supplemented their diet with meat, although the manner of their acquisition remains very much in debate.
The Acheulean technocomplex, though expansive in both time and space, represents a dynamic period in human evolutionary history. In this time period, australopithecines went extinct, genus Homo flourished, hominins reached the edges of the world (but hadn't quite made it to the Americas), cognitive capacity increased, meat-eating and cooking behavior picked up, and the handaxe tradition traveled from East Africa to Europe and India. There remain important questions regarding the possible cognitive or cultural underpinnings to the morphology of Acheulean tools, or absence thereof, as well as questions of their distribution and use. Whether or not the Acheulean technologies were static, the time period in which they were made and used was assuredly eventful. As a result, the better we understand the Acheulean, the better resolution we'll have for understanding a critical period in our evolution.