Introduction

This exercise has a number of objectives. These are:

1. To introduce you to the principles of fracture mechanics that govern the manufacture of stone tools.
2. To explain some of the specialized terminology that you may encounter when reading descriptions of stone tools.
3. To show you the attributes that archaeologists use to distinguish intentional modification of stone from natural or accidental modification.
4. To show what the principal stone tool types manufactured by early hominids were, and how they were made.

Fracture Mechanics

The term fracture mechanics simply refers to the forces that affect the way something breaks. In this particular case we are interested in the ways in which particular kinds of stone break. Fracture mechanics help to explain why there is a right and a wrong way to work stone in the process of tool making. It also helps to explain why certain types of stone are much better for tool making than others, and why they were thus preferentially selected by peoples in all parts of the world during all periods of time.

The two most important factors affecting the fracture mechanics of rocks are the graininess of the rock and the rock's elasticity.

Fracture Types

For our example, lets assume that there are four basic kinds of rock structures, as shown above. These are crystals, conglomerates, homogenous large particle rock, and homogenous small particle rock. The structure of each of these four types of rock affect the way in which they will break. Lets go on to see how they break.

Crystal Fracture

Crystals will shear along crystal planes.

Show Crystal Fracture

Conglomerate Fracture

Conglomerates tend to break irregularly and will not produce a sharp edge.

Show Conglomerate Fracture

Homogenous Large Particle Fracture

A homogenous, large particle material will exhibit more regular fracturing, but will not develop very sharp edges.

Show Large Particle Fracture

Homogenous Small Particle Fracture

A homogenous, small particle material will exhibit the most regular fracturing, and will form very sharp edges.

Show Small Particle Fracture

Grain

The size of a rock's particles is often referred to as the graininess of the rock. Thus, the smaller the particles the more fine-grained the rock. Very fine grained rocks such as flint, chert, and chalcedony can produce extremely sharp edges. Obsidian, naturally formed glass from volcanic deposits, is technically a supercooled fluid and hence has no crystalline structure or grain at all. The edges produced by fracturing obsidian can literally be measured in microns!

In general, the very best materials for making stone tools are obsidian, and cryptocrystalline quartzes such as chert, jasper, etc.

Elasticity

The second factor affecting the fracture mechanics of rocks is their elasticity. Elasticity refers to the tendency of a material to rebound from the effects of a force applied to it. Elasticity varies along a continuum from brittle (no flexibility) to plastic (no elasticity). For example, crystalline iron pyrite (fools gold) shatters when you press a piece between a pocketknife blade and your fingernail. It has very little flexibility and hence is brittle. Pure gold, on the other hand will spread like butter under the same conditions. It is extremely flexible, but has no elasticity, so it can be molded like clay. Thus gold is plastic.

The ideal material for making stone tools is tough, but has enough flexibility to bend rather than break when force is applied to it, but has enough elasticity that it does not deform under force. Again, obsidian and the cryptocrystalline quartzes have just the right blend of flexibility and elasticity to be perfectly suited to stone tool manufacture.

Show Elasticity

Cone Fractures

The more elastic a material is, the more likely that it will tear or shear under extreme stress rather than shatter. Combine this tendency with a material composed of very small particles and you have the makings of an excellent raw material for the kind of technology applied to flintknapping.

The hallmark of a good raw material is that it will break in a cone, or section of a cone, when the right amount of force is applied in the right place. These are also called Hertzian cones after the man who first explained how they are formed. A good example of this principle is the ring fracture that occurs when a bee-bee (small lead pellet) strikes a window pane. The same principle applies when you strike a flake off of a chert core, with the exception that instead of a full ring fracture you get a conic section.

Show Cone Fractures

Flake Morphology

Core

A core is any piece of material that has had flakes removed from it. Thus, a core could be used only as a source of sharp flakes, as in this example. At other times, cores themselves might also be made into tools, in which case the resulting tool is called a core tool.

Flake

A flake is any material removed from a core, whether intentional or not. In some cases, the flakes themselves were meant to serve as tools. In other cases, the flake is further modified to make a tool. At other times, the flakes may just be the waste material from shaping, thinning, or resharpening a stone tool. This waste material is called debitage, and is one of the most important collections of lithic material that archaeologists study. By studying the waste flakes and failures, we can actually reconstruct the prehistoric production technology and gain valuable insight into an important component of prehistoric human behavior.

Flake Scar

The flake scar is the concave surface left on a core after a flake has been removed from it. The flake scar will show the reverse image of the bulb of percussion on the flake, and will also exhibit ripples on occasion. The flake scar is equivalent to the hole left in the window pane from our last example.

Cortex

The cortex of a core or flake is the weathered, outer surface of the rock. Archaeologists often examine flakes to determine the amount of cortex on them in order to gauge the stage of manufacture and the degree to which cores were being used to exhaustion.

Striking Platform

The striking platform is the prepared surface on both the flake and the core where the blow that detached the flake was struck. Striking platforms will have different characteristics depending on the technique that was used to remove the flake. For example, on this flake and core, the striking platform has only one surface, and is quite wide, indicating that the flintknapper wanted to detach a large, thick flake. The platform will often have half of a ring fracture right at the exact point where the detaching blow was struck.

Errailure

The errailure is a French term denoting a subsidiary flake scar on the bulb of percussion of a flake. These scars occur as a result of excessive force being applied in the removal of the flake. The bulb of percussion is compressed so much that its elastic response is violent enough to cast secondary flakes off of itself.

Bulb of Percussion

The bulb of percussion is the conic section resulting from the fracturing of the rock. Depending on the amount of force in the detaching blow, the bulb of percussion can be very pronounced. The bulb is the result of the compression of the rock due to impact, and it is the elastic rebound from this compression that actually detaches the flake from the core.

Ripples

Ripples can often be observed on flakes made of obsidian and other very fine-grained materials. These radiating waves in the stone are actually deformations of the rock resulting from the shock wave that accompanied the detaching blow. They look like frozen ripples on a pond after a pebble has been tossed into it.

Hatchure Lines

Hatchure lines occur in flakes where extreme force was used in their removal from the core. The lines are actually hairline cracks resulting from interference shock waves bouncing around within the rock before the flake actually detaches itself. In the most extreme cases, these interfering shock waves can actually cause the flake to shatter as it is being detached.

Basic Techniques

There are four basic techniques that have been employed in the manufacture of stone tools. These four techniques are:

1. Hammer and Anvil
2. Bipolar
3. Hard Hammer
4. Soft Hammer

The following sections will explain each of these techniques in turn.

Hammer and Anvil Technique

The hammer and anvil technique for removing flakes from a core is perhaps one of the oldest documented methods. It is quite effective for making large flakes for direct use as tools, or for use as blanks from which shaped tools can be made. This technique entails using the core as a hammer, and striking the edge of the core against a large, stationary rock (the anvil) in order to remove a flake.

There are a number of disadvantages to the technique, however. The principal disadvantage is that the flintknapper does not have a great deal of control over the flake removal process. A second disadvantage is that the flakes removed in this manner fly up and away from the anvil, becoming very dangerous projectiles for anyone standing nearby.

Show Hammer and Anvil Technique

Bipolar Technique

The bipolar technique is a modification of the hammer and anvil technique. In bipolar flaking, the core is placed on the anvil for support, and then struck with a large heavy hammer. The compression from both ends of the core cause it to shatter into hundreds of flakes, some of which will be large enough, and of the right shape for use as tools. This technique is often found in areas where the only reliable source of workable stone is rounded river cobbles that are extremely hard to work in any other fashion.

The principal disadvantages to the bipolar technique are that there is very little control over the flake making process, and it wastes a great deal of raw material to get a few usable flakes.

Show Bipolar Technique

Hard Hammer Percussion Technique

Both of the techniques already discussed depend on percussion to remove a flake from a core. Hard hammer percussion, as the name implies, relies on the same principles, but provides more control over how the flake is detached. In hard hammer flaking, the core is held in one hand, and struck with a hammerstone. Technically, the hammerstone must be made of a material that is harder that the core material so that it does not shatter in the flintknapper's hands. By using hard hammer percussion, the experienced flintknapper has very good control over where the flake will be detached and the size of the flake.

Show Hard Hammer Technique

Soft Hammer Percussion Technique

While both hard and soft hammer methods take advantage of the fact that cyrptocrystalline rocks all break according to the Hertzian Cone principle, soft hammer percussion adds an added dimension of control to the process. In soft hammer flaking, a hammer or baton of material softer that the core is used. This could be soft limestone, deer antler, bone, or hardwood. Striking the core with the baton initiates a fracture according to the cone principle, but the soft hammer material tends to catch the edge of the flake, allowing the experienced flintknapper to actually help pull the flake off of the core. This works because the stone is actually shearing or tearing, rather than shattering, so it is a controlled breakage process.

Show Soft Hammer Technique

Pressure Flaking Technique

Pressure flaking is used for the final trimming and sharpening of the edges of stone tools. It is also often the method employed to sharpen tools during their use-life. Generally, pressure flaking is done with a durable, flexible tool such as a piece of antler tine. The technique takes advantage of the elasticity of the stone to actually peel thin flakes off of the core material. The more elastic the material, the better it is for pressure flaking. Thus, the finest examples of long, thin pressure flakes come from obsidian specimens.

Show Pressure Flaking Technique

Lower Paleolithic Stone Tool Technologies

In this section you will be introduced to some of the earliest stone tool technologies, such as those found at Olduvai Gorge. You will also be provided with information on some more advanced techniques for making stone tools. The stone tool technologies covered in this section include:

1. The Pebble Tool Tradition
2. The Chopper-Chopping Tool Tradition
3. The Acheulean Handaxe Tradition

The Pebble Tool Tradition

The very first stone tools were probably naturally broken, sharp-edged rocks that were casually picked up, used and discarded. There is probably no way that we will ever know how long this type of behavior persisted in hominid prehistory.

At some point, however, early hominids began purposely selecting specific raw materials, and making their own sharp-edged stone tools. The earliest manifestation of this behavior has been called the Pebble Tool Tradition, because it entailed the sharpening of pebbles and small cobbles through the bifacial (two-sided) removal of flakes. Although it was thought for years that the sharpened pebbles were the desired end product; new evidence from the analysis of microscopic wear patterns on the flakes that had been considered waste products indicates that the flakes may actually have been the tools, used for general purpose cutting.

Side Chopper from Site DK at Olduvai Gorge

Note the way in which this piece has been bifacially flaked to produce a sharp ridge along the right side and both ends. This is a fairly typical example of what have been termed pebble tools. Note also how it appears to have been battered along the mid portion of the right side.

Show Me How It Was Made

The Chopper-Chopping Tool Tradition

The Chopper-Chopping Tool Tradition was a logical outgrowth of the Pebble Tool Tradition. The primary goal of the Pebble Tool Tradition was probably the manufacture of sharp edged flakes. The cores, however, would also have been useful as heavy chopping tools. It is the regular diversification of the toolkit, incorporating tools made of sharp flakes and shaped core chopping tools that defines the boundary between the Pebble Tool Tradition and the Chopper-Chopping Tool Tradition. The latter had an extreme longevity, particularly in what are now China and Southeast Asia - about 1.5 million years without a significant change in technology!

Chopper from Site DK at Olduvai Gorge

Note how much more heavily worked this specimen is compared to the side chopper illustrated previously. This piece is also bifacially worked, but to a much more regular sharp edge on the upper left in the side view (left image).

Show Me How It Was Made

The Acheulean Handaxe Tradition

The next major technological advance in the production of stone tools is exhibited in the Acheulean Handaxe Tradition. Although the number of different types of tools used by peoples employing the Acheulean handaxes also increased compared to the Chopper-Chopping Tool Tradition, the real hallmark of the handaxe tradition is the craftsmanship and efficiency displayed in the production of the handaxes themselves.

The progressive refinement of lithic tool production, changing techniques to produce more cutting edge per unit of raw material, really becomes obvious when comparing the two earliest traditions to this one. This trend of increasing the efficiency of tools and raw material use characterizes the shift between major tool traditions. The Acheulean Tradition had a great longevity, also on the order of 1.5 million years, but was more confined to Africa, the Middle East, and western and central Europe.

Late Stage European Acheulean Handaxe

Note the excellent control exhibited in the shaping of this tool. Also note that all of the cortex has been removed. Finally, compare the amount of effective cutting edge on this tool to the amount of effective cutting edge on the large pebble chopper illustrated in that section. This technique is clearly an improvement in efficiency as well as technique.

The Acheulean Handaxes were made in very much the same way that the other two types of tools were manufactured. That is, they were produced by bifacial flaking using the hard hammer technique for initial shaping. A soft hammer technique was then used for final shaping and to produce a thin, sharp cutting edge. The last step was more common in the latter portion of the time period when these tools were being manufactured. The real distinction in the manufacture of these tools is the higher degree of selectivity in the choice of raw material, more control in the shaping of the tool, and the removal of larger, thinner shaping/thinning flakes.

If you are working on Assignment 4-2, then you should return to the Exercise menu, by clicking on the "Main" button below, to continue at this point. You have just been introduced to the basic principles of lithic technology. The techniques and the major tool types illustrated in this exercise have all been found in the deposits at Olduvai Gorge. We hope that this introduction will help you in the exercises that follow.

Introduction to Middle Paleolithic Tool Technology

As you saw in the introduction to stone tool technology presented with the material on Olduvai Gorge, an appreciation for changes in the manufacturing technology of stone tools is critical to our understanding of the development of early human societies.

You have already seen the preliminary part of this stack on the basics of fracture mechanics and the early technologies up to the Acheulean Handaxe Industry. You may want to review some of this material as you go along. The two sections to concentrate on for this exercise are the descriptions of the Levallois Technique and the Disc Core Technique, which are presented in order after the Acheulean.

Middle Paleolithic Tool Technologies

In this section you will be introduced to two stone technologies found associated with Middle Paleolithic deposits. The most important point for you to remember about the Middle Paleolithic stone technologies is that the emphasis shifted from core tools, like the Acheulean Handaxe, to flake tools like the Levallois point. Certainly, even at Olduvai, hominids had been taking advantage of sharp-edged flakes and even modifying them for specific tasks. The important difference in the Middle Paleolithic is that cores were being carefully shaped to produce flakes of a predetermined size and shape. The flakes were then further modified into both simple and complex tools.

The stone tool technologies covered in this section include:

1. The Levallois Technique
2. The Disk Core Technique

The Levallois Technique

The Levallois technique of core preparation and flake removal is the earliest of the core preparation technologies. The technology works in four distinct stages. First the edges of a cobble are trimmed into a rough shape. Second, the upper surface of the core is trimmed to remove cortex and to produce a ridge running the length of the core, Third, a platform preparation flake is removed from one end of the core to produce an even, flat striking platform for the blow that will detach the flake. Finally, the end of the core is struck at the prepared platform site, driving a longitudinal flake off of the core following the longitudinal ridge.

There are two distinct advantages to this technique. The first is that the flakes removed in this manner are already in a preliminary shape, and only require minor modification before being put to use. Second, more usable cutting edge per pound of raw material can be made this way than can be made by producing core tools.

Levallois Dart Point

Note how the final shape of this tool closely corresponds to the initial shape of the core from which it was struck. Also, notice how little edge trimming was necessary in order to get a very keen cutting edge on this tool. With care, a number of flakes could be removed from one core, producing much more usable cutting edge with less waste than if the core were thinned into a tool itself.

Show Me How It Was Made

The Disk Core Technique

The Disk Core Technique is not significantly different from the Levallois Technique. The technology still depends on careful core shaping and preparation in order to remove ready-to-use flakes for tools. The principal difference in the Disk Core Technique is that even more refinement and skill went into the core preparation so that more flakes could be removed from one core. Thus, the Disk Core technique is really a refinement of trends started by the Levallois technique. The exhausted cores left behind by this process often look like small disks with multiple flake scars, hence the name.

An Exhausted Disk Core

The most important thing to note about the Disk Core Technique is its efficiency. Using this technique a skilled flinknapper could produce many more usable tools from a single piece of raw material than was possible using any of the other techniques previously discussed.

Show Me How It Was Made

The process you have just seen would then be repeated, first working the other side of the core, then trimming off the rough top and bottom flake scars, perhaps removing tool flakes from the opposite end of the core. Three to five tools could probably be manufactured from a core this size by a skilled craftsman. Eventually, of course, the core would become too small and thin to produce more tools and would be discarded. This final exhausted discoidal form is all the evidence that we have of this remarkable improvement in the efficiency of lithic technology attained by Neanderthals and archaic Homo sapiens.

You have just been introduced to the two major tool manufacturing techniques in use during the Middle Paleolithic period. If you are working on Assignment 5-2, then you should return to the Exercise menu, by clicking on the "Main" button below, to continue at this point.

Upper Paleolithic Tool Technologies

As you should know from your readings, the Upper Paleolithic was a period of incredible diversity and technological innovation. Lithic technology also underwent an important change during this time. The trend towards increasing the efficiency of stone tool production reached its pinnacle during this period with the development of Blade Technology and the tools that blade making made possible. In this section we will discuss two topics:

1. Blade Technology
2. Burin Manufacturing

Prismatic Blade Technology

Few events in human prehistory rival the technological break-through inherent in the manufacture of prismatic blades. While using prepared core techniques such as the Disk Core and Levallois Core may have improved production efficiency by two-fold, blade technology improved it more than one hundred-fold! Provided that reasonably good raw materials were at hand, this new technology made it possible to manufacture large quantities of very sharp, straight cutting edges for use by themselves or as part of compound tools while using very little raw material. The blades, in turn, made it possible to manufacture such very useful implements as burins. These two tools, blades and burins, opened up a whole new world of wood and bone working with an ease and efficiency never previously matched.

A Prismatic Blade

Note the relatively even, parallel sides, and the ridge providing strength in the cross-section. The material efficiency stems from the fact that because of their cross-section, blades could be made very thin and long. The narrower the blades were, the more blades that could be made from each core, with no loss in the amount of cutting edge.

Show Me How It Was Made

Burin Blades

As we mentioned in the introduction to blade technology, the ability to manufacture fairly uniform, thin blades opened up a whole new world of simple and complex tool for Upper Paleolithic peoples. One of the most important of these tools was the burin or micro-burin. Although we have examples of burins as far back as the middle deposits at Olduvai, it is only in the Upper Paleolithic that burins become the highly refined gouging and engraving tool that we typically think of when the term burin is used. The burin, in turn, allowed these peoples to manufacture another extremely important tool for life in the cold latitudes - the bone needle. Burins were used to gouge bone and antler in parallel tracks. The bone could then be split out in uniformly narrow blanks. The blanks then had an eye drilled into them, and were ground down to the proper diameter and sharpness. With this very important tool, fitted clothing for protection from the extreme cold could be made.

Burin Made on a Blade

The thin cross-section of the blade made the perfect platform for creating a tool with a very sharp but strong fine point. The angle of the snapped-off portion of the blade served to reinforce the burin for work engraving and gouging tough materials such as bone and antler.

Show Me How It Was Made

Show Me How It Was Used

Summing It All Up

Over the course of the past several exercises, starting with the exploration of Olduvai Gorge and ending here, you have been introduced to major developments in stone tool manufacturing and use. This section will briefly sum the major points made.

• First, stone tool making and use can be demonstrated to have an extreme antiquity, dating to at least 1.75 million years ago. It may be that hominids were using stone tools earlier, but beyond a certain point it is extremely difficult to distinguish intentional usewear from naturally occurring wear, especially given the time depth involved.
• Second, the basic techniques of stone tool manufacturing, hammer and anvil, bipolar, and hard and soft hammer flaking; also have great antiquity. Only pressure flaking appears to develop later, but became quite common during the Middle Paleolithic and is in evidence on a wide variety of preshaped flake tools. Thus, the history of lithic technology is marked by changes in the way in which these techniques were applied rather than by marked changes in the basic techniques. After all, there are only so many ways to break a rock to make a sharp edge! The real changes occurred in the strategies for combining these techniques into increasingly efficient methods for manufacturing useful implements.
  
• Third, through time the variety of stone tool forms increases dramatically. As we saw at Olduvai, the earliest industries consisted of only a few basic types of tools dominated by choppers, and supplemented with a variety of expediency tools such as sharp flakes that were likely the by-product of chopper manufacture. As we progress through time to the Early Acheulean the variety of tool types increases slightly. In the Middle Paleolithic, the variety of tool types is staggering. This period is typified by more highly refined tools manufactured for very specific purposes. The Upper Paleolithic continues the trend with very task-specific tools being manufactured on highly standardized blanks - blades.
  
• Fourth, there is a trend through time for producing more cutting edge per unit of raw material. In the Chopper-Chopping Tool and Acheulean Industries, one core tool and perhaps a few usable flakes could be manufactured from a single pound of raw material. In the case of the Acheulean Handaxes, the result was a very useful multipurpose tool that would last for quite awhile, but which would eventually wear out after a few resharpenings, and which only had a few inches of usable cutting edge.
  
  In the Middle Paleolithic, with the adoption of the Levallois and especially the Disk Core Techniques, core tools were largely replaced by flake tools made from preshaped cores. About ten times as much usable cutting edge could be produced from the same amount of material used to make an Acheulean Handaxe. The trend culminated in the Upper Paleolithic with the development of Blade Technology. Using this technique, roughly 100 times the amount of useful cutting edge could be produced from the same quantity of raw material.
  
• Fifth, the increasing refinement of stone tools was accompanied by increases in the complexity of the process of manufacturing them and in the investment of time and energy that each tool represented. For example, a usable Acheulean Handaxe could be made with 25 well placed blows in one step. That process would probably take only a few minutes. An Upper Paleolithic blade knife would take up to 251 flake removals in nine fairly complex steps! While raw material was being used more efficiently, the tools were taking longer to manufacture because of the necessary additional steps required to use the material more efficiently. Part of this process also involved a change in the role that the stone tool played. Where initially the stone tool was the tool, in the Middle and Upper Paleolithic the stone tool was becoming just a part of a more complex compound tool adapted to a very specific task. A compound tool such as a hunting spear would have a stone point attached to a hardwood foreshaft, that was in turn socketed into a main shaft, that was in turn hooked with an atl-atl or throwing stick.
  

Conclusion

All of these general trends are readily apparent in the archaeological record, and are recorded by the stone tools and production debris left behind. Certainly, these phenomena are interesting in and of themselves, but their real importance lies in the fact that they are clues. Clues to fundamental changes in human behavior through time. Review the information you have been presented thus far on the evolution of the hominid line, global environmental changes during the Pleistocene, and the five trends in lithic technology just discussed. Use information from both your readings and Web exercises. Then, for each of the four major lithic technologies (Chopper-Chopping Tool, Acheulean, Levallois, and Blade) write a brief synthetic paragraph that discusses the way in which that technology correlates with hominid evolutionary changes and possible environmental adaptations. Interleave your response in your Study Guide.

Department of Anthropology, UCSB

Brian M. Fagan and George H. Michaels
Comments to web author: michaels@id-archserve.ucsb.edu

All contents copyright © 1996, The Regents of The University of California. All rights reserved.
Revised: January 29, 1996
URL: http://id-archserve.ucsb.edu/www/Anth3/Exercises/LithicTech/LithicTech.html