These pages have been left in this location as a service to the numerous websites around the world which link to this content. The original authors are no longer at the University of Leeds, and the former Centre for Human Biology became the School of Biomedical Sciences which is now part of the Faculty of Biological Sciences.
Dr. Bill Sellars
As I mentioned in yesterday's lecture, tool use is considered to be a sign of higher cognitive abilities. It was once thought to be one of the features that set humans apart from other animals, and indeed, if one looks at the range and sophistication of the tools that humans use, then this is indeed true. However, tool use has been seen in a number of primate species, including early hominins, and the study of these tools provides important information concerning the evolution of the human tool using abilities.
This lecture is about tool use in NHP and tool use in early hominins up to early humans about 100,000 ya.
Tools can thus be very simple - a bunch of leaves used as a sponge to carry water, for example, of a stick to help scratch the animal's back. This sort of tool which requires no alteration to be functional, is sometimes described as a "naturefact".
In this context, an "artefact" is a tool that has been crafted: altered in some way to make it more suitable for the job in hand. For example, chimps have been know to chew their termite fishing sticks so that they fit better into the holes in the termite mounds. A chewed stick is now an artefact. Oswald has produced a table that broadly categorizes artefacts in terms of increasing complexity:
1. Reduction: reduce mass of functional form (e.g.. our chewed stick, or a flaked flint.
2. Conjunction: combine 2 or more units to make tool (e.g.. a flint headed spear, or a hafted axe)
3. Replication: conjunction but with 2 or more similar units required (e.g.. a double pronged fishing spear)
4. Linkage: physically distinct forms in combination (e.g.. a bow and arrow)
In the context of this lecture, I shall cover categories 1 and 2, since 3 and for are almost certainly the sphere of true humans.
1. Not all animals seem capable of learning to use tools
2. They don't seem to "understand" their tools (e.g.. banging the ground next to the nut)
3. Other members of the group are able to learn to use tools by observation
4. In captivity, they will use other tools to perform particular tasks (e.g.. honey dipping with straw)
It has been suggested that capuchin tool use is not a result of cognitive ability (though capuchins do have bigger brains than would be expected for such small monkeys), but are an almost accidental feature of their destructive foraging methods. However, in captivity, they have been observed to produce conjunction tools: sticking 2 pieces of straw together to make a longer probe to reach rewards farther away from the cage than they could reach with a single straw, which may indicate quite a large degree of sophistication.
There is certainly a very large difference in their enthusiasm for tool use.
Here is a list of the observed use of tools among chimps (#CMC180). As you can see, there is a very great difference in the observed tool usage at the different sites. Tool use would therefore appear to be a very cultural phenomena - use is restricted to, and passed on within a limited population.
In captivity, all the great apes have used a wide variety of tools that have not been seen in the wild: from branches used as pitons to aid escape to flaked stone tools to cut ropes tying shut boxes containing food. (#CMC 221) It might be suggested that these animals have an untapped tool making and using ability that is simply not required in their current environment. This begs the question, "Why?" Was the common ancestor of the great apes a much more avid tool user with its environment encouraging tool use at any opportunity? Or is tool using ability just a largely latent feature of having a large brain (for whatever ultimate reason great apes have large brains, be it foraging or social complexity). We will probably never know the answer.
Break for video of chimp tool use.
What is much easier to spot are the tools made of siliceous rocks. These rocks (of which flint is the best known example) are fairly homogeneous and without any obvious crystal structure which fracture in a "conchoidal" (shell-like) fashion when hit. This pattern of fracturing is usually relatively easy to spot, and produces very characteristic flakes with what are termed as "shock ripples" and a "bulb of percussion". This latter is a rounded bulge near the point of impact of the hammer used to create the flake.
A safer way of producing these chunky flakes is by direct percussion using a suitable hammer stone (a granite pebble for example). This same hammer can then be used to touch up the initial flake to produce a better cutting edge. (#CGPM 108) The tools produced are relatively crude and quite varied.
If animal classification caused you sleepless night, then stone tool classification is even worse! Stone tools don't really have homologous features as such, and almost certainly form a continuum from simple to more complex.
Acheulean technologies are the first examples of "bifaces". These are stone tools that are flaked on both sides (#CGPM 127). This requires rather more skill, and a great many more strikes per tool. The tools produced certainly look better, and the fact that they are rather thinner than monofacial chopper would indicate that they were superior for cutting meat etc.
We also have evidence of wooden and bone tools associated with H. erectus all from Ambrona or Torralba in Spain.
In addition there appears to be a certain style associated with these and subsequent tools. Tool appearance rather than just functionality seems to have some importance. This may be an indication of some sort of higher level cognition.
The first of these techniques is referred to as "blade core technology" (#NSUF 52). Where multiple long blades are struck from the core. This (and other core technologies) require more accurate striking of the core, and modern flint knappers often use indirect percussion (hammer hitting a chisel made of wood, bone or antler) to improve precision.
The second technique is "flake core" technology (Levallois flakes) (#NSUF 58) which produces rather regular, flattened flakes rather than blades. The key feature of these flakes is that, made properly, both sides are convex so that the flake is both strong and sharp (#NSUF 59)
It is clear that early hominins had a cultural progression of tool use that was not specifically linked to one species or another (though some may claim this).
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