Lithics
The manufacture of prehistoric stone tools
We refer to lithic artifacts as those created through rock flintknapping or grinding. Due to their high preservation, they represent a valuable source of information for archaeologists.
Suitable rocks must be selected for flintknapping: they must be fine-grained, homogeneous and free of defects such as fissures. These rocks fracture in a particular way, called conchoidal. By applying precise blows with sufficient force, controlled and predictable fractures can be generated.
In most cases, flintknapping is based on two basic techniques: percussion and pressure, which are not mutually exclusive and can be combined in different ways.
Percussion flaking
Percussion flaking consists of striking a mass of rock (which we call a nodule) with a hammer (A), with the aim of producing a fracture that is as controlled as possible. The most common hammers are made of rock (hard percussion), but it is also possible to use horn, bone or wood (soft percussion).
If the procedure is successful, it will cause a fracture in the nodule and a fragment of rock with the desired shape and size will be released, called a flake (C) and from this moment on, the fractured nodule is called a core (B).
Example 1: Production of laminar artifacts
We call laminar artifacts (or blades) to those elongated artifacts that have a length that is at least twice their width. In order to produce this type of artifacts, the application of a set of specific techniques (that is, a method) is necessary.
At the end of the process, a set of blades and a pyramidal or prismatic core are obtained.
Example 2: The Levallois method
This flintknapping method owes its peculiar name to a French town where it was first defined. Over time it was observed that it was repeatedly used in very different times and places, presenting many variants.
It consists of producing a core of a specific shape (similar to a turtle) with the aim of obtaining a series of large, slightly curved flakes, with a very thick end and a very sharp edge.
Pressure flaking
As its name indicates, in pressure flaking the flakes are removed by using pressure on a stone mass.
Pressure is applied using a rounded-tipped bone or horn instrument. In this case, too, precision and control are required to achieve the desired fracture.
In the region, this technique was mainly applied to artifacts to remove small flakes in order to shape them or produce a certain edge (1). This procedure is called retouch. Pressure was also used on small cores (2). It must be pointed out that a retouch can also be made by percussion.
Why study lithic artifacts?
Archaeologists have developed specific studies aimed at interpreting artifacts in technological terms. We define technology as the entire technical system of a society, including all the artifacts produced and the knowledge associated with their production and use.
This allows us to understand practical aspects related to how artifacts were produced and used: How was the raw material obtained? How was it worked? What accounts for the final shape of the artifacts? What function did they serve?
By understanding these aspects we are also thinking of artefacts as expressions of a particular social and cultural dynamic, with its historical particularities. The world of technology offers a wide variety of possible solutions, but over time each culture chooses from the entire range of options those that are consistent with its particular vision.
The Santa Cruz river basin
The Levallois method has been identified in different sectors of the basin, at different times. The variant used, called the centripetal recurrent method, is the most complex of all and seeks to obtain several flakes, planning their size and shape. This is achieved by repeatedly flintknapping the core, taking care of keeping its shape.
The earliest evidence of the utilization of this method is from the upper basin of the Santa Cruz river, dating back to 4.300 years before the present. Its use persisted until approximately 1.800 years ago. The reasons for the adoption and abandonment of this flaking method are still being investigated.
Near the mouth of the Santa Cruz river into the Atlantic Ocean, evidence of the use of this method has been found between 2.800 and 1.200 years ago. In this case, the research is focused on evaluating the reasons for its utilization and if it can be due to the moment of human groups, or if they represent two independent cases.
Laminar artifacts have been recovered at different times:
- At sites located to the west, on the southern bank of the river, this type of artifacts was produced from approximately 6.200 to 4.300 years ago. It is always found in small quantities and occasionally, taking advantage of the natural shape of the nodules and employing flexible flaking techniques.
- Between 1.900 and 1.300 years before present, there is more specific evidence at sites on both sides of the basin, located both in the west and in the middle basin. Small quantities of laminar artifacts were produced, but using a much more complex knapping method. Research is underway to determine whether these changes are related to the social dynamics of hunter-gatherer groups or whether they are linked to the environment, among other factors.
The Chico river basin
Laminar artifacts have been recovered in several surface collections recovered throughout the study area. In all cases, rock varieties of very good quality were used.
Laminar artifacts corresponding to human occupations over the last 5.000 years were recovered at some sites in the area.