Human Evolution
Stone artefacts are humankind’s most enduring legacy. Stone tools were first made in Africa about 3.3 million years ago and stone flaking has continued uninterrupted to the present day. It is safe to say that most, if not all, of our direct hominin and human ancestors knew the rudiments of controlled flaking. It is only in recent millennia that a sizeable percentage of humans could go through life without this skill.
Scores of flakes are struck from a stone to initially produce a tool and to maintain it through its use-life. Because of this, combined with the exceptionally deep chronology of this technology, it can be conservatively estimated that hominins have produced more than one artefact for each square metre of our planet’s land surface. Stone tools endure on the landscape and cannot be easily ignored, and, as the archaeologist Richard Bradley put it, ancient peoples were ‘forced to use these scraps of ancient material culture to understand their place in the world’. Archaeologists use the scientific method to continue to do this today, and research over the last 160 years has created the ‘standard sequence’ of technological change over the course of human evolution.
The timing and general pattern of early changes in stone-flaking technology is relatively well established, although the empirical data around the details is continually changing with new fieldwork discoveries. And given that these archaeologists are studying the very foundations of our ‘place in the world’, the stakes are high, and the ongoing debates about the meanings of these empirical data are loud and passionate, as they have been for generations of archaeologists. These models of stone tools, and the accompanying text, will give you some idea of the nature of the empirical evidence about the emergence and early development in humankind’s technological adaptation to the environment, and the ways that archaeologists interpret this evidence.
Oldowan Industry
Our earliest evidence for stone flaking is stone tools dating to 3.3 million years ago from the site of Lomekwi 3 in the West Turkana region of Kenya. These early ‘Lomekwian’ tools—about 20 artefacts were excavated from secure context—are unsophisticated and may have resulted from the use of stone as hammers and percussion tools. Deliberate, fully-controlled stone-flaking emerges with the Oldowan Industry by ca. 2.6 million years ago. The famous palaeoanthropologist Mary Leakey named the industry after the earliest stone tools excavated from Olduvai Gorge in Tanzania from the 1930s to the 1960s. The Oldowan is conventionally said to end at about 1.76 million years ago, when it is supplanted by the Acheulean Industry, but Oldowan-style tools continued to be made throughout human history. The Oldowan Industry is primarily attributed to the hominin Homo habilis, although australopithecines or other a different species of Homo may have also made these stone tools.
Oldowan stone tools were made by striking flakes by hard-hammer percussion, mostly from water-rolled pebbles of volcanic stones. Stone-flaking was well-controlled and many of the flakes were expertly struck, showing that these earlier hominin stoneworkers knew to strike near the edge of the stone behind zones of high mass on the core, to choose a platform angle of less than 90 degrees (the ‘acute angle rule’), and to strike the core with a glancing blow.
Many of the cobbles were reduced bifacially—a scar produced previously was used as the platform to strike a flake off of the opposite face. Some cobbles were rotated frequently during reduction and many platforms struck, resulting in multiplatform cores. Some archaeologists argue that the hominins removed flakes to deliberately produce designed (if rather crude-looking) tools, but a more parsimonious explanation is that flaking was algorithmic, driven by the mechanical restrictions of stone-working combined with the configuration of the particular stone.
Cobble cores may have been used as heavy-duty tools, but the hominin stoneworkers were most likely after the sharp-edged flakes. Current thinking is that these sharp-edged flakes allowed access to meat for the first time, which in turn gave our ancestors and adaptive edge, and allowed for brain growth during subsequent evolution. Oldowan knappers trimmed the margins of some of these flakes, a process called retouching, perhaps to resharpen them. They also smashed pebbles and flakes on anvils, creating more flakes—a process called bipolar flaking. Cobble hammerstones are also common at Oldowan sites, probably to break open bones for marrow, as well as to use as hammers in stone-flaking. Heavily worn hammerstones in Oldowan assemblages are called ‘spheroids’, and some archaeologists have suggested that these were deliberately-shaped tools.
Homo floresiensis
In 2003, the Australian-Indonesian team led by archaeologist Mike Morwood of the University of New England discovered a skeleton of a tiny individual in Liang Bua Cave on the island of Flores, Indonesia. Rokus Awe Due, a local bone expert, immediately observed that although the sizes of the bones indicated that the individual was a female about the height of a 5-year-old child, the wear on the teeth and the advanced fusion of sutures suggested she was an adult in her 30s. Also, anatomical features of the skull, mandible, and limb bones were highly unusual. Palaeoanthropologist Peter Brown confirmed Rokus’s observations, and in 2004 the research team, led by Morwood and Brown, announced a new species of human to the scientific community, which they named Homo floresiensis. Morwood nicknamed the find ‘Hobbit’ after the famous story by J. R. R. Tolkien and the popular Peter Jackson film.
Homo floresiensis was of tiny stature, about 1.0 metre tall, with a brain the size of an orange. After prolonged initial controversy, the scientific community accepted it as a new hominin species and a cousin species to modern Homo sapiens. H. floresiensis lived in Liang Bua Cave from about 190,000 to 60,000 BP, but further research by Morwood’s team excavating sites in the So’a Basin of Flores eventually discovered ancestral H. floresiensis remains dating to about 700,000 BP and stone tools that must have been made by these hominins dating to about 1.0 million years ago.
The evolutionary origins of H. floresiensis are still debated, but the most parsimonious explanation is that the hominin descended from a population of Homo erectus—well-documented on the island of Java to the west—made its way to Flores by 1.0 million years ago and became isolated. Once on the island, the well-known selective forces on isolated land masses, known as the ‘island rule’, began to take effect, and the hominin’s body (about the same average size as a modern adult H. sapien) began to shrink, reaching its diminutive stature by 500,000 BP and evolving into a distinct species. An alternative hypothesis is that the colonising hominin was not H. erectus, but was instead a smaller and evolutionarily more primitive hominin species (an australopithecine or Homo habilis) that somehow walked from Africa to Flores without leaving archaeological evidence in between. In this scenario, it too was subjected to the island rule, leading to dramatic changes to body shape, but less radical changes in size.
Landing on Flores from a jumping-off point on Java or Sulawesi meant that Homo erectus was leaving behind familiar mainland Asian plants and animals to confront on Flores an exotic and unfamiliar mix of species. Flores was populated by Komodo dragons, giant storks and rats, white-headed vultures, crocodiles, giant tortoises, and small endemic elephants called stegodon. An often-overlooked aspect to this story is that these colonising hominins were able to take on and survive the challenges of Flores for over 900,000 years because they had an ‘ace in the hole’: the technological adaptation provided by stone tools. The global history of our genus Homo shows that technology is an unparalleled means for squeezing the maximum amount of energy possible from the environment.
The stone tools made by H. floresiensis, first described by MoST Director Mark Moore—the stone tool analyst for Morwood’s research team—are technologically similar to Oldowan Industry stone tools from Africa. Volcanic cobbles were reduced into flakes, which were the principal tool of these hominins. Cores were reduced bifacially and frequently rotated, resulting in multiplatform and bifacial ‘centripetal’ cores. Sometimes larger flakes were themselves flaked to produce more sharp-edged flakes, particularly in Liang Bua Cave. Flakes were also retouched to shape the edges or resharpen them, and a perforator-like projection occurs on some retouched flakes and cobbles. Some flakes and cores were placed on an anvil and smashed, truncating them into splinters with right-angled tool edges. The bipolar technique was known to H. floresiensis, but most flaking was done by expert hard-hammer direct percussion. Despite being the size of a modern human five-year-old, these hominins were able to remove well-struck flakes measuring up to 12 centimetres long from very tough volcanic stones.
There are some profound lessons to learn from the Flores story. First, while stone-tool technology ensured the population’s survival for some 50,000 generations, it could not buffer our hominin cousins from the extremes of the selective pressures encountered on Flores. Their skeletal anatomy and body shape morphed and natural selection profoundly affected their posture, the way they walked and ran, and the movement of their arms. Even more significantly, their cranial capacity decreased to become on-par with a modern chimpanzee’s. Yet Homo floresiensis didn’t lose the capacity to make stone tools. Their brains reorganised to retain the complex cognitive abilities necessary to make and use their toolkit, and the dramatic changes in body shape must have accommodated the physical requirements of forceful stone-flaking. The hominin’s technological ability was crucial to the survival of these enigmatic creatures, but it could not break them free from the strictures of the island rule.
The H. floresiensis story, told through their stone tools, may be a lesson for all of us. Technology may be essential for survival, but it does not serve as a firewall against the powerful forces of natural selection.
Acheulean Industry
The Acheulean Industry was named after stone artefacts recovered in the 1850s from ancient river terraces in a quarry at Saint-Acheul (Amiens), in France. The Oldowan and Acheulean industries define the Lower Palaeolithic period. The Acheulean emerged in Africa about 1.76 million years ago, and the end-date is generally thought to be about 100,000 BP, so Acheulean tools were likely made by more than one hominin species (including Homo habilis and Homo erectus). The key artefact type of the Acheulean is the ‘handaxe’, so-named because early researchers thought they were chopping tools that were held in the hand. These objects are bifacial: flaked to two opposite faces from a common platform edge. The platform edge is very sharp and is presumed to be the working edge of the tool.
Bifacial handaxes play a prominent role in the history of archaeology, and science more generally. John Frere was the first to recognise the significance of stone handaxes when he found examples of them in ancient sea deposits at Hoxne in Suffolk, alongside bones of extinct animals. He suggested in his 1797 paper that they came from ‘a very remote period indeed; even beyond that of the present world.’ Workmen discovered many handaxes at Hoxne, and ‘emptied baskets full of them into the ruts of the adjoining road’.
But the scientific establishment was not ready for such heresy, so the paper was ignored for another 40 years until similar handaxe finds were published by Boucher de Perthes in France. These French artefacts (and, later, the Hoxne handaxes) were subsequently accepted as ancient tools when the leading geologist of the time, Joseph Prestwich, along with a founder of stone tool studies, John Evans, visited France in 1858 and became convinced by the stratigraphic evidence. The acceptance of great antiquity for humans was an important backdrop for Charles Darwin’s book on evolution by natural selection.
Handaxes have since become one of the most iconic stone tools from human evolution and the most-studied tool type from the Lower Palaeolithic. Handaxes are common in the archaeological record of Africa, Europe, West Asia, and India, but are rare or absent from East and Southeast Asia and Indonesia. Most archaeologists would agree that the Acheulean saw a development in handaxe morphology, from relatively crude early versions at about 1.76 million years ago, to highly symmetrical tools by about 500,000 years ago. A ‘classic’ later Acheulean handaxe demonstrates bilateral symmetry (symmetry around the length axis), with a thick proximal end (‘butt’) and a thin, tapered distal end (‘tip’). The earliest handaxes were made by percussion flaking using a hammerstone, and later handaxes may have been finished using a soft hammer, such as a bone. Handaxes continued to be made into the Middle Palaeolithic in some regions, including by Homo neanderthalensis in Europe.
Handaxes are intriguing because they are found in vast numbers on some sites, far more than you might expect for a simple cutting or chopping tool. Also, handaxes dominated stone technology for some 1.66 million years. Both of these patterns demand explanation, and the archaeological literature is rife with debate. The dominant view is that these patterns reflect the slowly-evolving cognition and tool-mediated social behaviour in our hominin ancestors. The data that drives these debates is mostly from studies of handaxe shape, augmented by detailed statistical analysis of attribute measurements, a field of study called morphometrics.
In a contrasting view, the archaeologist Iain Davidson argued that archaeologists cannot reliably determine whether an artefact was a deliberate product or simply an accidental byproduct of making something else. He coined the phrase ‘the finished artefact fallacy’ to refer to the common assumption that archaeologists’ typological categories reflect design intentions of ancient hominins. It is possible that handaxes were the discarded cores from making flakes for tools, and the various symmetries and attributes identified on handaxes may be due to restrictions of the mechanics behind stone-flaking, rather than deliberately-produced features. Further, identifying a class of tools as a ‘handaxe’ based on shape and symmetry tended to ignore the fact that these objects are a subset of continuous variation. For instance, some handaxes are elongated versions of bifacial cobble cores like those seen in the Oldowan, and there are a large number of bifacial tools in all Oldowan and Acheulean assemblages that are not elongated (and therefore not classified as ‘handaxes’, so not included in morphometric analyses). In this case, analysts are studying archaeologists’ conventions regarding symmetry and what they choose to analyse, and not hominin design intentions.
Levallois Method
The Middle Palaeolithic emerged from the Lower Palaeolithic by about 250,000 BP in Africa and 150,000 BP in Europe. In the Lower Palaeolithic, flakes struck from cores tended to be amorphous in shape and size. Towards the end of the Lower Palaeolithic and into the Middle Palaeolithic, cores began to be shaped so that a flake with a predetermined shape could be struck off. Archaeologists refer to this as a ‘prepared core’ technology because the core was carefully prepared by prior anticipatory flaking before striking off the desired objective flake. The objective flake was then retouched and used as the tool. Prepared-core technologies require more advanced cognitive abilities than the simpler preceding approaches, and their emergence is considered by many archaeologists to signal an important change in hominin evolution. The Levallois Method is the earliest widespread example of prepared core technology.
The Levallois Method was practiced by hominins in Africa, Europe, and West Asia. ‘Levallois’ refers to the Levallois-Perret suburb of Paris, where the method was first described. The Levallois Method is associated with ‘archaic’ species of Homo, including Homo neanderthalensis, and a new hominin that appeared on the scene—Homo sapiens. The Levallois Method persisted to about 40,000 BP, followed by a greater emphasis on ‘blade’ technologies—flakes that are more than twice as long as they are wide. The formal Levallois Method is absent from Asia and Australia.
The Levallois Method involves striking a large, invasive flake from a bifacial core. To successfully remove a flake, the flintknapper must strike behind a zone of high mass. The crack undercuts the mass, which falls away as the flake. In simpler approaches to flake-making, zones of high mass are removed opportunistically as they are identified on the core. In contrast, the Levallois Method involves carefully-considered strategic flaking to create a zone of high mass of a specific shape. The carefully-shaped high mass is then removed as the objective flake, which is used as the tool. This involves a two-step process: 1) remove the mass-shaping flakes, and 2) remove the objective flake. This is cognitively more complex than removing flakes opportunistically, because removing each of the shaping flakes also involves creating and removing zones of high mass. The structure of the process is ‘hierarchical’ because a successful objective flake depends on successful core shaping.
A key feature of the Levallois Method is that only one face of the core was invasively flaked—first to set up the high mass for the objective flake, and then the removal of that high mass. In contrast, the opposite face was usually flaked non-invasively, just enough to provide platform surfaces to strike the flakes from the ‘objective’ face (the face from which the objective flake would be removed). The stone on either face can be conceptualised as a ‘volume’, and, in this case, one volume is used differently from the other—the volumes are also hierarchically related.
In one variety of the Levallois Method, the objective face was shaped in such a way that the surface was domed, and this dome created the high mass subsequently undercut by the objective flake. Archaeologists refer to this shaping process as manipulating the ‘convexities’ on the core, by the process of removing stone as small flakes. The configuration of the flake scars from this process define the zone of high mass. In another Levallois Method variant, the high mass is made triangular in shape, and the objective flake removing this mass is thus triangular in shape.
Striking that final objective flake required the platform to be just right in terms of platform angle and depth. To achieve this, much platform adjustment was sometimes necessary, resulting in multifacetted platforms. A core might be reworked several times, producing multiple objective flakes. The Levallois Method was accomplished by direct percussion using hard hammerstones.
The Levallois objective flakes were retouched and used as cutting and scraping tools, but some may have been used as spearpoints (although this is disputed by some archaeologists). The latter examples include Levallois flakes ‘predetermined’ to be triangular in shape as struck from the core, but others were retouched into this triangular shape. Levallois flake variants from North Africa were retouched at the proximal end to form a projecting stem, creating artefacts called ‘Aterian Points’. The stem was presumably inserted into a spearshaft or handle.
The way that the Levallois Method is defined, applied, and interpreted is not without controversy. The Levallois Method was recognised by French researchers from the middle 19th Century, but was more formally defined by the European lithic expert François Bordes in 1950. But by the 1980s European archaeologists seemed to apply it uncritically to all sorts of bifacial assemblages—and particularly flakes—from all over the world. Partly as a consequence of this, the French archaeologist Éric Böeda redefined Levallois in geometric and conceptual terms (as described above), thus restricting identification of the Levallois Method to reduction sequences that demonstrate these very specific criteria. This definition is in general use today, although many analysts are far less strict that Böeda, and many technologies described as ‘Levallois’ do not fit Böeda’s formal definition.
Eoliths
The term eoliths (literally ‘dawn stones’) refers to objects once thought to be the earliest stone tools. They are now known to be examples of natural fracture—not deliberately fashioned tools—and, as such, are rarely a topic of modern archaeological research. However, in the late 19th and early 20th centuries, eoliths were one of the central topics in the developing field of stone artefact analysis. The 30-year controversy over whether they were natural or cultural in origin was exceptionally heated and emotional in certain quarters, particularly in Britain.
The stakes of the debate were high: because eoliths were often found in gravels dating as early as the Miocene, far earlier than the early obvious tools such as handaxes, the implications for interpreting human evolution were profound. Indeed, the Eolithic was considered by some scientists at the time to be a formal industry that preceded the Palaeolithic. Eoliths were identified in association with the fraudulent Piltdown fossils, and, given their contemporary respectability, were thought to lend credence to the find. Some creationists continue to insist that eoliths are, in fact, deliberately-fashioned tools that undermine Darwinian evolution because of their presence in such old geological deposits. Eoliths still generate passionate feelings in some quarters today.
Eoliths were first published by the Oxford professor Joseph Prestwich in 1889 to describe stones found by Benjamin Harrison in Kent, England, and the term was borrowed from the French archaeologist Gabriel de Mortillet as shorthand to refer to similar objects from around England and Europe. Eoliths were collected from flint- or chert-rich river gravels or beach terraces. The supposed artefacts were acknowledged as exceptionally crude compared to later stone tools, but this in itself was not a problem because it supported preconceptions about technological progress. Elaborate typologies of eoliths were developed by their proponents, such as J. Reid Moir and E. Ray Lankester.
In 1905 the French archaeologist Marcellin Boule was the first to argue that eoliths are, in fact, examples of natural fracture, followed soon after by similar criticisms by Samuel Hazzledine Warren through the 1910s. Warren’s studies are particularly important in the history of stone artefact studies—and archaeology generally—because he was among the first to apply experiments, and the scientific method of hypothesis testing, to resolve a question about prehistory. He also linked the results of his experiments to observations of natural fracture in the field. The design and results of those early experiments explain the natural forces at work that can mimic deliberate stone-flaking, and this is accepted by archaeologists as the most parsimonious explanation for eoliths.
