Hand axe
A hand axe (or handaxe or Acheulean hand axe) is a prehistoric stone tool with two faces that is the longest-used tool in human history, yet there is no academic consensus on what they were used for. It is usually made from flint or chert. It is characteristic of the lower Acheulean and middle Palaeolithic (Mousterian) periods, roughly 1.6 million years ago to about 100,000 years ago, and used by homo erectus and other early humans, but rarely homo sapiens. Its technical name (biface) comes from the fact that the archetypical model is a generally bifacial and  almond-shaped (amygdaloidal) lithic flake. Hand axes tend to be symmetrical along their longitudinal axis and formed by pressure or percussion. The most common hand axes have a pointed end and rounded base, which gives them their characteristic almond shape, and both faces have been knapped to remove the natural cortex, at least partially. Hand axes are a type of the somewhat wider biface group of two-faced tools or weapons. Hand axes were the first prehistoric tools to be recognized as such: the first published representation of a hand axe was drawn by John Frere and appeared in a  British publication in 1800. Until that time, their origins were thought to be natural or supernatural. They were called "thunderstones", because popular tradition held that they had fallen from the sky during storms or were formed inside the earth by a lightning strike and then appeared at the surface. They are used in some rural areas as an amulet to protect against storms. Hand axe tools were possibly used to butcher animals; to dig for tubers, animals and water; to chop wood and remove tree bark; and/or process vegetal materials. Other scholars have proposed that hand axes were used to  throw at prey; for a ritual or social purpose; or possibly as a source for flake tools. 1969 in the 2nd edition of World Prehistory, Grahame Clark proposed an evolutionary progression of flint-knapping industries (also known as complexes or technocomplexes) in which the "dominant lithic technologies" occurred in a fixed sequence where simple Oldowan one-edged tools were replaced by these more complex Acheulean hand axes, which were then eventually replaced by the even more complex Mousterian tools made with the Levallois technique. Terminology. Four classes of hand axe are: While Class 4 hand axes are referred to as  formalized tools, bifaces from any stage of a lithic reduction sequence may be used as tools. (Other biface typologies make five divisions rather than four.) French antiquarian André Vayson de Pradenne introduced the word in 1920. This term co-exists with the more popular "hand axe" (), that was coined by Gabriel de Mortillet much earlier. The continued use of the word biface by François Bordes and Lionel Balout supported its use in France and Spain, where it replaced the term "hand axe". Use of the expression "hand axe" has continued in English as the equivalent of the French ( in Spanish ), while biface applies more generally for any piece that has been carved on both sides by the removal of shallow or deep flakes. The expression is used in German; it can be literally translated as hand axe, although in a stricter sense it means "fist wedge". It is the same in Dutch where the expression used is which literally means "fist axe". The same locution occurs in other languages. However, the general impression of these tools was based on ideal (or classic) pieces that were of such perfect shape that they caught the attention of non-experts. Their typology broadened  the term's meaning. Biface hand axe and bifacial lithic items are distinguished. A hand axe need not be a bifacial item and many bifacial items are not hand axes. Nor were hand axes and bifacial items exclusive to the Lower Palaeolithic period in the Old World. They appear throughout the world and in many different pre-historical epochs, without necessarily implying an ancient origin. Lithic typology is not a reliable chronological reference and was abandoned as a dating system. Examples of this include the "quasi-bifaces" that sometimes appear in strata from the Gravettian, Solutrean and Magdalenian periods in  France and Spain, the crude bifacial pieces of the Lupemban culture (9000 B.C.) or the pyriform tools found near Sagua La Grande in Cuba. The word "biface" refers to something different in English than in French or in Spanish, which could lead to many misunderstandings. Bifacially carved cutting tools, similar to hand axes, were used to clear scrub vegetation throughout the Neolithic and Chalcolithic periods. These tools are similar to more modern adzes and were a cheaper alternative to polished axes. The modern day villages along the Sepik river in New Guinea continue to use tools that are virtually identical  to hand axes to clear forest. "The term "biface" should be reserved for items from before the Würm II-III interstadial", although certain later objects could "exceptionally" be called bifaces. "Hand axe" does not relate to "axe", which was overused in lithic typology to describe a wide variety of stone tools. At the time the use of such items was not understood. In the particular case of Palaeolithic hand axes the term axe is an inadequate description. Lionel Balout stated, "the term should be rejected as an erroneous interpretation of these objects that are not 'axes. Subsequent studies supported this  idea, particularly those examining the signs of use. Materials. Hand axes are mainly made of flint, but rhyolites, phonolites, quartzites and other coarse rocks were used as well. Obsidian, natural volcanic glass, shatters easily and was rarely used. Uses. No academic consensus describes their use, but it is commonly agreed that the hand axe was some form of unhafted all-purpose tool. The pioneers of Palaeolithic tool studies first suggested that bifaces were used as axes despite the fact that they have a sharp border all around. Other uses seem to show that hand axes were a multi-functional tool , leading some to describe them as the "Acheulean Swiss Army knife". Other academics have suggested that the hand axe was simply a byproduct of being used as a core to make other tools, a weapon, or was perhaps used ritually. Wells proposed in 1899 that hand axes were used as missile weapons to hunt prey – an interpretation supported by Calvin, who suggested that some of the rounder specimens of Acheulean hand axes were used as hunting projectiles or as "killer frisbees" meant to be thrown at a herd of animals at a water hole so as to stun one of  them. This assertion was inspired by findings from the Olorgesailie archaeological site in Kenya. Few specimens indicate hand axe hafting, and some are too large for that use. However, few hand axes show signs of heavy damage indicative of throwing, modern experiments have shown the technique to often result in flat-faced landings, and many modern scholars consider the “hurling” theory to be poorly conceived but so attractive that it has taken a life of its own. As hand axes can be recycled, resharpened and remade, they could have been used for varied tasks. For this reason it may be  misleading to think of them as "axes", they could have been used for tasks such as digging, cutting, scraping, chopping, piercing and hammering. However, other tools, such as small knives, are better suited for some of these tasks, and many hand axes have been found with no traces of use. Baker suggested that since so many hand axes have been found that have no retouching, perhaps the hand axe was not itself a tool, but a large lithic core from which flakes had been removed and used as tools (flake core theory). On the other hand, there are many hand  axes found with retouching such as sharpening or shaping, which casts doubt on this idea. Other theories suggest the shape is part tradition and part by-product of its manufacture. Many early hand axes appear to be made from simple rounded pebbles (from river or beach deposits). It is necessary to detach a 'starting flake', often much larger than the rest of the flakes (due to the oblique angle of a rounded pebble requiring greater force to detach it), thus creating an asymmetry. Correcting the asymmetry by removing material from the other faces, encouraged a more pointed (oval) form factor . (Knapping a completely circular hand axe requires considerable correction of the shape.) Studies in the 1990s at Boxgrove, in which a butcher attempted to cut up a carcass with a hand axe, revealed that the hand axe was able to expose bone marrow. Kohn and Mithen independently arrived at the explanation that symmetric hand axes were favoured by sexual selection as fitness indicators. Kohn in his book "As We Know It" wrote that the hand axe is "a highly visible indicator of fitness, and so becomes a criterion of mate choice." Miller followed their example and said that hand axes  have characteristics that make them subject to sexual selection, such as that they were made for over a million years throughout Africa, Europe and Asia, they were made in large numbers, and most were impractical for utilitarian use. He claimed that a single design persisting across time and space cannot be explained by cultural imitation and draws a parallel between bowerbirds' bowers (built to attract potential mates and used only during courtship) and Pleistocene hominids' hand axes. He called hand axe building a "genetically inherited propensity to construct a certain type of object." He discards the idea that they  were used as missile weapons because more efficient weapons were available, such as javelins. Although he accepted that some hand axes may have been used for practical purposes, he agreed with Kohn and Mithen who showed that many hand axes show considerable skill, design and symmetry beyond that needed for utility. Some were too big, such as the “Great Hand Axe” found in Furze Platt, England that is 30.6 cm long(other scholars measure it as 39.5 cm long). Some were too small - less than two inches. Some were “overdetermined”, featuring symmetry beyond practical requirements and showing evidence of unnecessary attention  to form and finish. Some were actually made out bone instead of stone and thus were not very practical, suggesting a cultural or ritual use. Miller thinks that the most important clue is that under electron microscopy hand axes show no signs of use or evidence of edge wear. Others argue that little evidence for use-wear simply relates to the particular sedimentological conditions, rather than being evidence of discarding without use. It has been noted that hand axes can be good handicaps in Zahavi's handicap principle theory: learning costs are high, risks of injury, they require physical strength , hand-eye coordination, planning, patience, pain tolerance and resistance to infection from cuts and bruises when making or using such a hand axe. Evidence from wear analysis. The use-wear analysis of Palaeolithic hand axes is carried out on findings from emblematic sites across nearly all of Western Europe. Keeley and Semenov were the pioneers of this specialized investigation. Keeley stated, """The morphology of typical hand axes suggests a greater range of potential activities than those of flakes""". Many problems need to be overcome in carrying out this type of analysis. One is the difficulty in observing larger pieces with  a microscope. Of the millions of known pieces and despite their long role in human history, few have been thoroughly studied. Another arises from the clear evidence that the same tasks were performed more effectively using utensils made from flakes: Keeley based his observations on archaeological sites in England. He proposed that in base settlements where it was possible to predict future actions and where greater control on routine activities was common, the preferred tools were made from specialized flakes, such as racloirs, backed knives, scrapers and punches. However, hand axes were more suitable on expeditions and in seasonal camps , where unforeseen tasks were more common. Their main advantage in these situations was the lack of specialization and adaptability to multiple eventualities. A hand axe has a long blade with different curves and angles, some sharper and others more resistant, including points and notches. All of this is combined in one tool. Given the right circumstances, it is possible to make use of loose flakes. In the same book, Keeley states that a number of the hand axes studied were used as knives to cut meat (such as hand axes from Hoxne and Caddington). He identified that the point of  another hand axe had been used as a clockwise drill. This hand axe came from Clacton-on-Sea (all of these sites are located in the east of England). Toth reached similar conclusions for pieces from the Spanish site in Ambrona (Soria). Analysis carried out by Domínguez-Rodrigo and co-workers on the primitive Acheulean site in Peninj (Tanzania) on a series of tools dated 1.5 mya shows clear microwear produced by plant phytoliths, suggesting that the hand axes were used to work wood. Among other uses, use-wear evidence for fire making has been identified on dozens of later  Middle Palaeolithic hand axes from France, suggesting Neanderthals struck these tools with the mineral pyrite to produce sparks at least 50,000 years ago. Macroscopic traces. Some hand axes were used with force that left clearly visible marks. Other visible marks can be left as the scars from retouching, on occasion it is possible to distinguish them from marks left by the initial manufacture. One of the most common cases is when a point breaks. This was seen at sites in Europe, Africa and Asia. One example comes from the El Basalito site in Salamanca, where excavation uncovered fragments of a  hand axe with marks at the tip that appeared to be the result of the action of a wedge, which would have subjected the object to high levels of torsion that broke the tip. A break or extreme wear can affect a tool's point or any other part. Such wear was reworked by means of a secondary working as discussed above. In some cases this reconstruction is easily identifiable and was carried out using techniques such as the "coup de tranchet" (French, meaning "tranchet blow"), or simply with scale or scalariform retouches that alter an edge's symmetry and  line. Forms. The most characteristic and common shape is a pointed area at one end, cutting edges along its side and a rounded base (this includes hand axes with a lanceolate and amygdaloidal shape as well as others from the family). The axes are almost always symmetrical, despite studies showing that symmetry doesn’t help in tasks such as using a hand axe for skinning animals. While there is a “typical” shape to most hand axes, there are some displaying a variety of shapes, including circular, triangular and elliptical—calling in to question the contention that they had a constant  and only symbolic significance. They are typically between long, although they can be bigger or smaller. They were typically made from a rounded stone, a block or lithic flake, using a hammer to remove flakes from both sides of the item. This hammer can be made of hard stone, or of wood or antler. The latter two, softer hammers can produce more delicate results. However, a hand axe's technological aspect can reflect more differences. For example, uniface tools have only been worked on one side and partial bifaces retain a high proportion of the natural cortex of the tool  stone, often making them easy to confuse with chopping tools. Further, simple bifaces may have been created from a suitable tool stone, but they rarely show evidence of retouching. Later hand axes were improved by the use of the Levallois technique to make the more sophisticated and lighter Levallois core. In summary, hand axes are recognized by many typological schools under different archaeological paradigms and are quite recognisable (at least the most typical examples). However, they have not been definitively categorized. Stated more formally, the idealised model combines a series of well-defined properties, but no set of these properties  are necessary or sufficient to identify a hand axe. History and distribution. The oldest known Oldowan tools were found in Gona, Ethiopia. These are dated to about 2.6 mya. Early examples of hand axes date back to 1.6 mya in the later Oldowan (Mode I), called the "developed Oldowan" by Mary Leakey. These hand axes became more abundant in mode II Acheulean industries that appeared in Southern Ethiopia around 1.4 mya. Some of the best specimens come from 1.2 mya deposits in Olduvai Gorge. They are known in Mousterian industries. By 1.8 mya early man was present in Europe. Remains  of their activities were excavated in Spain at sites in the Guadix-Baza basin and near Atapuerca. Most early European sites yield "mode 1" or Oldowan assemblages. The earliest Acheulean sites in Europe appear around 0.5 mya. In addition, the Acheulean tradition did not spread to Eastern Asia. In Europe and particularly in France and England, the oldest hand axes appear after the Beestonian Glaciation–Mindel Glaciation, approximately 750,000 years ago, during the so-called "Cromerian complex". They became more widely produced during the Abbevillian tradition. The apogee of hand axe manufacture took place in a wide area of the  Old World, especially during the Riss glaciation, in a cultural complex that can be described as "cosmopolitan" and which is known as the Acheulean. The use of hand axes survived the Middle Palaeolithic in a much smaller area and were especially important during the Mousterian, up to the middle of the Last glacial period. Hand axes dating from the lower Palaeolithic were found on the Asian continent, on the Indian subcontinent and in the Middle East (to the south of parallel 40° N), but they were absent from the area to the east of the 90° E meridian . Movius designated a border (the so-called Movius Line) between the cultures that used hand axes to the west and those that made chopping tools and small retouched lithic flakes, such as were made by Peking man and the Ordos culture in China, or their equivalents in Indochina such as the Hoabinhian. However, Movius hypothesis was found incorrect when many hand axes made in Palaeolithic era were found in 1978 at Hantan River, Jeongok, Yeoncheon County, South Korea for the first time in East Asia. Some of them are exhibited at the Jeongok Prehistory Museum, South Korea. The Padjitanian culture  from Java was traditionally thought to be the only oriental culture to manufacture hand axes. However, a site in Baise, China shows that hand axes were made in eastern Asia. In North America, hand axes make up one of the dominant tool industries, starting from the terminal Pleistocene and continuing throughout the Holocene. For example, the Folsom point and Clovis point traditions (collectively known as the fluted points) are associated with Paleo Indians, some of the first people to colonize the new world. Hand axe technology is almost unknown in Australian prehistory, although a few have been found. Construction. Experiments  in knapping have demonstrated the relative ease with which a hand axe can be made, which could help explain their success. In addition, they demand relatively little maintenance and allow a choice of raw materials–any rock will suffice that supports a conchoidal fracture. With early hand axes, it is easy to improvise their manufacture, correct mistakes without requiring detailed planning, and no long or demanding apprenticeship is necessary to learn the necessary techniques. These factors combine to allow these objects to remain in use throughout pre-history. Their adaptability makes them effective in a variety of tasks, from heavy  duty such as digging in soil, felling trees or breaking bones to delicate such as cutting ligaments, slicing meat or perforating a variety of materials. Later examples of hand axes are more sophisticated with their use of two layers of knapping (one made with stone knapping and one made with bone knapping). Lastly, a hand axe represents a prototype that can be refined giving rise to more developed, specialised and sophisticated tools such as the tips of various projectiles, knives, adzes and hatchets. Analysis. Given the typological difficulties in defining the essence of a hand axe, it is important when  analysing them to take account of their archaeological context (geographical location, stratigraphy, the presence of other elements associated with the same level, chronology etc.). It is necessary to study their physical state to establish any natural alterations that may have occurred: patina, shine, wear and tear, mechanical, thermal and / or physical-chemical changes such as cracking, in order to distinguish these factors from the scars left during the tool's manufacture or use. The raw material is an important factor, because of the result that can be obtained by working it and in order to reveal the economy and movement  of prehistoric humans. In the Olduvai Gorge the raw materials were most readily available some ten kilometres from the nearest settlements. However, flint or silicate is readily available on the fluvial terraces of Western Europe. This means that different strategies were required for the procurement and use of available resources. The supply of materials was the most important factor in the manufacturing process as Palaeolithic artisans were able to adapt their methods to available materials, obtaining adequate results from even the most difficult raw materials. Despite this it is important to study the rock's grain, texture, the presence of  joints, veins, impurities or shatter cones etc. In order to study the use of individual items it is necessary to look for traces of wear such as pseudo-retouches, breakage or wear, including areas that are polished. If the item is in a good condition it is possible to submit it to use-wear analysis, which is discussed in more detail below. Apart from these generalities, which are common to all carved archaeological pieces, hand axes need a technical analysis of their manufacture and a morphological analysis. Technical analysis. The technical analysis of a hand axe tries to discover each  of the phases in its "chaîne opératoire" (operational sequence). The chain is highly flexible, as a toolmaker may focus narrowly on just one of the sequence's links or equally on each link. The links examined in this type of study start with the extraction methods of the raw material, then include the actual manufacture of the item, its use, maintenance throughout its working life, and finally its disposal. A toolmaker may put a lot of effort into finding the highest quality raw material or the most suitable tool stone. In this way more effort is invested in obtaining a  good foundation, but time is saved on shaping the stone: that is, the effort is focused on the start of the operational chain. Equally the artisan may concentrate the most effort in the manufacture so that the quality or suitability of the raw material is less important. This will minimize the initial effort, but will result in a greater effort at the end of the operational chain. Tool stone and cortex. Hand axes are most commonly made from rounded pebbles or nodules, but many are also made from a large flake. Hand axes made from flakes first appeared at the  start of the Acheulean period and became more common with time. Manufacturing a hand axe from a flake is actually easier than from a pebble. It is also quicker, as flakes are more likely to be closer to the desired shape. This allows easier manipulation and fewer knaps are required to finish the tool; it is also easier to obtain straight edges. When analysing a hand axe made from a flake, it should be remembered that its shape was predetermined (by use of the Levallois technique or Kombewa technique or similar). Notwithstanding this, it is necessary to note a tool 's characteristics: type of flake, heel, knap direction. The natural external cortex or "rind" of the tool stone, which is due to erosion and the physical-chemical alterations of weathering, is different from the stone's interior. In the case of chert, quartz or quartzite, this alteration is basically mechanical, and apart from the colour and the wear it has the same characteristics as the interior in terms of hardness, toughness etc. However, flint is surrounded by a limestone cortex that is soft and unsuitable for stone tools. As hand axes are made from a tool stone's core, it  is normal to indicate the thickness and position of the cortex in order to better understand the techniques that are required in their manufacture. The variation in cortex between utensils should not be taken as an indication of their age. Many partially-worked hand axes do not require further work in order to be effective tools. They can be considered to be simple hand axes. Less suitable tool stone requires more thorough working. In some specimens the cortex is unrecognisable due to the complete working that it has undergone, which has eliminated any vestige of the original cortex. Types. It  is possible to distinguish multiple types of hand axe: Production. Older hand axes were produced by direct percussion with a stone hammer and can be distinguished by their thickness and a sinuous border. Mousterian hand axes were produced with a soft billet of antler or wood and are much thinner, more symmetrical and have a straight border. An experienced flintknapper needs less than 15 minutes to produce a good quality hand axe. A simple hand axe can be made from a beach pebble in less than 3 minutes. The manufacturing process employs lithic reduction. This phase is commonly thought of  as the most important in hand axe fabrication, although it is not always used, such as for hand axes made from flakes or a suitable tool stone. An important concern is the implement that has been used to form the biface. If multiple implements were used, it is essential to discover in what order they were used and the result obtained by each one. The most common implements are: Hard hammer faces. Hand axes can be made without subsequent reworking of the edges. A hammerstone was the most common percussive tool used during the Acheulean. The resulting artefact is usually  easily recognizable given its size and irregular edges, as the removed flakes leave pronounced percussion bulbs and compression rings. A hammerstone produces a small number of flakes that are wide and deep leaving long edges on the tool as their highly concave form yields curving edges. The cross-section is irregular, often sub-rhombic, while the intersection between the faces forms an acute angle of between 60° and 90° degrees. The shape is similar to that of the core as the irregularities formed during knapping are not removed. The notches obtained were exploited in the production sequence. It  is common that this type of manufacture yields """partial bifaces""" (an incomplete working that leaves many areas covered with cortex), "unifaces" (tools that have only been worked on one face), "bifaces in the Abbevillian style" and """nucleiform bifaces""". This type of manufacturing style is generally an indication of the age when a tool was made and with other archaeological data can provide a context that allows its age to be estimated. Hard hammer faces and edges. These hand axes have a more balanced appearance as the modification consists of a second (or third) series of blows to make the piece  more uniform and provide a better finish. The modification is often called retouching and is sometimes carried out using invasive retouching or using softer, marginal, shallow blows that are only applied to the most marked irregularities leaving scale-like marks. The modification of edges with a hard hammer was carried out from the beginning of the Acheulean and persisted into the Musterian. It is therefore not useful as an indicator of chronology (in order for it to be considered as a marker it has to be accompanied by other complementary and independent archaeological data). The hand axes arising from this  methodology have a more classical profile with either a more symmetrical almond or oval shape and with a lower proportion of the cortex of the original core. It is not always the case that the retouching had the objective of reducing an edge's irregularities or deformities. In fact, it has been shown that in some cases the retouching was carried out to sharpen an edge that had been blunted by use or a point that had deteriorated. Soft hammer finish. Some hand axes were formed with a hard hammer and finished with a soft hammer. Blows that result in  deep conchoidal fractures (the first phase of manufacture) can be distinguished from features resulting from sharpening with a soft hammer. The latter leaves shallower, more distended, broader scars, sometimes with small, multiple shock waves. However, marks left by a small, hard hammer can leave similar marks to a soft hammer. Soft hammer finished pieces are usually balanced and symmetrical, and can be relatively smooth. Soft hammer works first appeared in the Acheulean period, allowing tools with these markings to be used as a "post quem" estimation, but with no greater precision. The main advantage of a soft hammer is that  a flintknapper is able to remove broader, thinner flakes with barely developed heels, which allows a cutting edge to be maintained or even improved with minimal raw material wastage. However, a high-quality raw material is required to make their use effective. No studies compare the two methods in terms of yield per unit weight of raw material, or the difference in energy use. The use of a soft hammer requires greater use of force by the flintknapper and a steeper learning curve, although it offers more flakes for less raw material. Soft hammer only. Hand axes made using only  a soft hammer are much less common. In most cases at least initial work was done with a hard hammer, before subsequent flaking with a soft hammer erased all vestiges of that work. A soft hammer is not suitable for all types of percussion platform and it cannot be used on certain types of raw material. It is, therefore, necessary to start with a hard hammer or with a flake as a core as its edge will be fragile (flat, smooth pebbles are also useful). This means that although it was possible to manufacture a hand axe using a  soft hammer, it is reasonable to suppose that a hard hammer was used to prepare a "blank" followed by one or more phases of retouching to finish the piece. However, the degree of separation between the phases is not certain, as the work could have been carried out in one operation. Working with a soft hammer allows a knapper greater control of the knapping and reduces waste of the raw material, allowing the production of longer, sharper, more uniform edges that will increase the tool's working life. Hand axes made with a soft hammer are usually more symmetrical and  smooth, with rectilinear edges and shallow indentations that are broad and smooth so that it is difficult to distinguish where one flake starts and another ends. They generally have a regular biconvex cross-section and the intersection of the two faces forms an edge with an acute angle, usually of around 30°. They were worked with great skill and therefore they are more aesthetically attractive. They are usually associated with periods of highly developed tool making such as the Micoquien or the Mousterian. Soft hammer manufacturing is not reliable as the sole dating method. Hand axes were created to  be tools and as such they wore out, deteriorated and/or broke during use. Relics have suffered dramatic changes throughout their useful lives. It is common to find edges that have been sharpened, points that have been reconstructed and profiles that have been deformed by reworking in order to extend the piece's useful lifetime. Some tools were recycled later, leading Bordes to note that hand axes "are sometimes found in the Upper Palaeolithic. Their presence, which is quite normal in the Perigordian I, is often due, in other levels, to the collection of Mousterian or Acheulean tools.". Morphology. Hand axes  have traditionally been oriented with their narrowest part upwards (presupposing that this would have been the most active part, which is not unreasonable given the many hand axes that have unworked bases). The following typological conventions are used to facilitate communication. The axis of symmetry that divides a biface in two is called the "morphological axis." The "main face" is usually the most regular and better worked face. The "base" (not the "heel") is the bottom of the hand axe. Dimensions and ratios. Hand axe measurements use the morphological axis as a reference and for orientation. In addition to length , width, depth, specialists have proposed a wide range of other physical quantities. The most common were proposed by Bordes and Balout: A and o can be used to delineate the contour's cross section and to measure the angles of the edges (provided this is not an area covered in the stone's original cortex). These angular measurements for the edges are made using a goniometer. Edge length, weight and the length of the chord described by the edges (if the piece has a transverse terminal bezel) can be measured. These measurements allow morphological and technical ratios to be established  (for example, the relationship between the weight and the length of the cutting edges, or the relationship between the hammer used to form the piece and the angle obtained etc.). The most commonly used coefficients were established by Bordes for the morphological-mathematical classification of what he called "classic bifaces" (Balout proposed other, similar indices): Bordes hand axe typology. The following guide is strongly influenced by the possibly outdated and basically morphological "Bordes method" classification system. This classification is particularly applicable to "classic hand axes", those that can be defined and catalogued by measuring dimensions and mathematical ratios, while disregarding  nearly all subjective criteria. """Distinguishing between different types of hand axes is not always easy. There is often no room for doubts, however, there are a number of cases where the difficulty is real.""" In the majority of cases, this system agrees with previously established categories (although slightly redefining them). Balout made a similar attempt at categorization. Non-classic specimens. Many specimens defeat objective classification. Bordes created a group he called "non-classic bifaces" to which mathematical indexes do not apply. The multi-use capability of a biface, including this type, conflicts with the technological simplicity of a cleaver, even  though their morphology and function may be similar. Tools sometimes categorized as bifaces. Hand axes constitute an important group artefacts from the Acheulean. They are particularly important in open air archaeological sites (Keelley suggested that they are less common in cave sites). Hand axes, chopping tools and trihedral picks are considered "core" utensils, which were commonly manufactured out of stones, blocks or rock nodules. However this grouping is problematic as these tools were often also fabricated from (large) flakes. Another common suggestion is to refer to flake tools as "micro industry," as opposed to the more general size referred to  as "macro industry", which includes hand axes and cleavers. However, some scrapers are as big as hand axes. Another group of tools commonly associated with hand axes is the "biface leafpoint tools" from the Lower and Middle Palaeolithic in the Old World. The difference between the two types is based on the latter's fine, light finishing with a soft hammer and in a morphology that suggests a specific function, possibly as the point of a projectile or a knife. Representatives of these tools include well known examples from the specialized literature: Importance. The hand axe helped establish that early  humans were capable of constructing relatively sophisticated tools that also reflected a sense of aesthetics. The 19th century publications of Frere, and more importantly of Boucher de Perthes, in France, described pieces that were balanced, symmetrical and crafted with a formal purity. Vilanova i Piera published similar works in Spain. This work was continued by Pérez de Barradas and del Prado at the start of the 20th century. As Leroi-Gourhan explained, it is important to ask what was understood of art at the time, considering the psychologies of non-modern humans. Archaeological records documenting rapid progress towards symmetry and  balance surprised Leroi-Gourha. He felt that he could recognize beauty in early prehistoric tools made during the Acheulean: Many authors refer only to exceptional pieces. The majority of hand axes tended to symmetry, but lack artistic appeal. Generally, only the most striking pieces are considered, mainly 19th or early 20th century collections. At that time a lack of knowledge regarding prehistoric technology prevented a recognition of human actions in these objects. Other collections were made by aficionados, whose interests were not scientific, so that they collected only objects they considered to be outstanding, abandoning humbler elements that were sometimes  necessary to interpret an archaeological site. Exceptions include sites methodically studied by experts where magnificently carved, abundant hand axes caused archaeologists to express admiration for the artists: The discovery in 1998 of an oval hand axe of excellent workmanship in the Sima de los Huesos in the Atapuerca Mountains mixed in with the fossil remains of "Homo heidelbergensis" reignited this controversy. Given that this is the only lithic remnant from this section of the site (possibly a burial ground), combined with the piece's qualities led it to receive special treatment, it was even baptized Excalibur and it became a  star item. However, the symbolic meaning of this example in particular, and hand axes in general, has multiplied in recent years, feeding both scientific and more general debate and literature. Basch offered this counterargument: Paradoxically, within the wide range of Acheulean objects, hand axes are one of the simplest tools. They do not require as much planning as other types of object, generally made from flakes, that are less striking but more sophisticated. Archaeologists have evidence of hand axes that are 1.2 million years old in Melka Kunturé (Ethiopia), but the oldest, from Konso-Gardula, could be 1.9 million years  old: Although it is now known that they are the heritage of a number of human species, with "Homo ergaster" the earliest, up until 1954 no solid evidence indicated who had fabricated hand axes: in that year, in Ternifine, Algeria, Arambourg discovered remains that he called "Atlanthropus", along with some hand axes. All the species associated with hand axes (from "H. ergaster" to H. "neanderthalensis") show an advanced intelligence that in some cases is accompanied by modern features such as a relatively sophisticated technology, systems to protect against inclement weather (huts, control of fire, clothing), and certain signs of spiritual  awareness (early indications of art such as adorning the body, carving of bones, ritual treatment of bodies, articulated language).