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TOOLS OF AFRICAN HISTORY: 10 METHODS
In the investigation and study of the history and life of earlier Africans and indeed humans generally, certain tools or techniques are employed without which most findings would be useless since nothing can be deduced from them. With the help of these techniques or tools, information can be obtained which provides knowledge about the origins and the way of life of earlier humans.
DENDROCHRONOLOGY
Also known as tree ring dating is employed to determine the age of trees or wooden objects or other related items such as buildings with wooden structures, furniture, etc.
With this method, the age of pieces of wood or wooden artefacts obtained in archaeology or from vintage works of art, like old panel paintings can be deduced.
It can even be used to determine the source of the wood used in the creation of such objects.
Because new growth in trees occurs in layers of cells near the bark, it results in predictable, visible growth rings caused by a response to climate changes.
Each ring corresponds to a complete season cycle which is a year. The oldest rings are in the middle while the more recent rings are around the edge. This enables the age of the wood to be accurately read.
Very old piece of wood with tree rings
However, dendrochronology almost all of the time cannot be single-handedly used to determine the age of wooden items. This is because to accurately and precisely determine the age of wood, a full sample of the edge is required which is absent on most wooden objects and artefacts.
There are other reasons dendrochronology is not single-handedly used. The wood might have been obtained from another structure, parts of the wood might have been replaced, or the wood used when felled might have been left for a significant number of years before it was finally used for creation.
This method of dating has its advantages. It is very easy to implement and simple to read; it does not require any cumbersome or expensive scientific process.
Also, dendrochronology does not only give info on the age of wooden objects. It can also provide data useful for dendroclimatology.
Dendroclimatology is the study of climatic and atmospheric conditions during different periods, using data obtained from the wood. For example, a wet year will produce thicker rings while a dry year will yield thinner rings.
Another of its advantage is in cases where the age of the sample is too recent to use the radiocarbon method, Dendrochronology can be effectively used to determine the age of the item. It can also be employed as a check mechanism for the radiocarbon method, in that after radiocarbon is used to determine the age of an object, the result can be double checked by using dendrochronology to see if it will yield a precise more recent date.
It is not without its disadvantages as well. Dendrochronology cannot be used to date wooden objects effectively. Also, its span is between 5000 to 8000 years, which is relatively short.
POTASSIUM-ARGON DATING
The Potassium-Argon method also written as K-Ar dating is used to date materials like rock or carbon. It is mostly employed by archaeologists for geochronology.
The process involves measuring the amount of argon (Ar) or rate of decay of the potassium content (K) in the material.
When a rock is formed, its potassium content slowly starts decaying into Argon.
Measuring the Argon content gives scientists an idea of the time elapsed since the formation of the rock.
The decay product Argon (Kr) freely escapes during rock formation when the material is still in its liquid or molten state. When the rock solidifies, overtime the unescaped argon starts to accumulate.
The amount of argon depends on factors like the purity and composition of the rock sample amongst other conditions. These factors affect the amount of argon released during decay and therefore introduces a margin of error while using the K-Ar method of dating.
A more accurate determination of the age of such materials using this technique must be with the consideration of some conditions such as environmental factors during the formation of the material and the exposure to open air or decreased pressure.
Normally the time elapsed since the recrystallization of the rock is determined by measuring the ratio of the Argon (Kr) accumulated to the potassium (K) remaining. And because Potassium has a long half-life, the K-Ar dating method can be used to more accurately determine the age of very old materials; more than 100,000 years.
Its use therefore in archaeology cannot be overemphasized.
It has its advantages. It can be used to date very old samples millions of years old. Because of this, it is very useful in dating human evolution in Africa. It can also be used to date volcanic eruptions and the forming of new landscapes.
Its disadvantage lies in the fact that it is most useful for areas with volcanic activity. Also, landscapes might have to be broken up so as to obtain reliable data.
RADIOCARBON DATING
Also called carbon-14 dating, this method is used to determine the age of anything that has lived. It does this by measuring the radioactive emissions from the dead organism.
Every living organism continues to emit radioactive C14 after it dies. The more time has elapsed since the organism died, the less C14 the sample will hold. Organisms that have been dead for longer will therefore have emitted more radioactive C14. By measuring the amount of C14 in a dead plant or animal, it provides information that can be used to calculate when the organism might have died; the older the sample the fewer C14 there is to be detected.
Samples as old as 50,000 years or even older can be reliably dated, the half-life of the C14 which is 5,730 years makes this possible.
There are two methods of radiocarbon dating, the Accelerator Mass Spectrometer (AMS) and the Radiometric methods.
This dating method developed around 1940 has had a profound effect on archaeology. Not only does it allow for more accurate dating than the other methods, but it also enables the comparison of dates of events across very far apart landscapes. It has also made possible the dating of the different transitional periods in history. Such as the end of the Ice age and the beginning of the Neolithic and bronze age.
Thermoluminescence Testing Process (source: http://www.oxfordauthentication.com)
THERMOLUMINESCENCE PROCESS
The thermoluminescence technique is very popular and widely used in the world of archaeology and historical findings study. It is used exclusively on ceramics and clay objects, pottery figurines or any such item containing crystalline materials. You might have probably guessed as the name suggests that this technique must have something to do with heat and light, well, you guessed right. Thermoluminescence is used to determine the age of crystalline materials like clay, ceramics, etc. This is done by measuring the item’s accumulated radiation dose since it was last heated or exposed to sunlight.
During the initial creation of such objects which undoubtedly involves the application of heat, electrons are dislodged and relocate in imperfections and crevices in the object, as the object ages more and more electrons dislodge. When the object is now subjected to the thermoluminescence process so as to determine its age, it is reheated which results in the electrons moving back to their places emitting light as they do so, this light or radiation is then measured. The older the object, the more radiation it emits.
Thermoluminescence although effective has its limitations, apart from the fact that it only works for crystalline materials, it can not be used to determine the age of such objects that are more than 35,000 years old.
Also, there is a possibility of the object getting damaged in the process.
It has its advantages as well. Although the limit to which it can determine the age of an object is 35,000, that figure is still a considerable length of time, and so the thermoluminescence technique is still very useful.
Also, the thermoluminescence technique prevails in situations where other techniques like radiocarbon would be pointless. The technique is also relatively cheap.
THE THREE AGE SYSTEM
The three age system is the categorization of history into time periods, basically three periods the Stone Age, Bronze Age, and the Iron Age.
This methodological concept vastly used in archaeology and physical anthropology was adopted in the 19th century.
It enables artefacts, events of late prehistory and early history to be structured into a discernible chronology.
This system of dating is useful in archaeology because it allows for archaeological finds and artefacts such as weapons, pottery, stone, jewellery, etc, to be easily dated to one of the three periods which gives an idea of when such object might have been created.
One drawback of this method of dating is that it does not attempt to narrow down dating, it merely gives an estimate which sometimes might not be accurate. Also, it is heavily based on the European perception of history; many societies of the world do not have or recognize these three major stages of history in their culture.
The advantage lies in its simplicity. It is an extremely cheap way to date objects, there are no complications whatsoever neither does it require scientific tests. Also, the categories are clear and distinct, any object found to have been classified to any of the categories instantly gives an idea of when it might have been created.
ACCELERATOR MASS SPECTROMETER DATING
This is a more precise type of radiocarbon dating. It is used for any organic sample that had once lived.
Radiocarbon dating methods primarily use modern standards like oxalic acid and other reference materials to determine the carbon 14 content of samples.
The samples are mostly archaeological and geological materials. The Accelerator Mass Spectrometer Dating technique(AMS) involves the acceleration of ions to extremely high kinetic energies, then followed by mass analyses.
What happens is that ions are accelerated via accelerator systems. The two accelerator systems used are cyclotron and the tandem electrostatic accelerator.
Accelerator Mass Spectrometer
In the mass analyses, a magnetic field is applied to the moving charged particles. This alters the course of the moving particles. If the charged particles are of the same speed but different masses as in the case of carbon isotopes, it causes the heavier particles to be the least deflected. Deflectors at the different angles of deflection then count the particles.
Accelerator mass spectrometry counts the number of carbon 14 atoms available in the sample.
It uses an apparatus known as the Mass spectrometer which detects the atoms of specific elements based on their atomic weights.
The mass spectrometer employs a method to identify carbon 14 in a sample while ignoring the more abundant isotopes that crowds the carbon 14 signal.
The number of carbon 14 atoms is not the only information gotten after an AMS run. Quantities of carbon 12 and carbon 13 are also retrieved; all these data can be used to determine the level of fractionation of the sample.
The AMS dating method has its drawbacks.
This method of dating is very expensive even more expensive than its sister radiometric dating, costing millions of dollars to establish and maintain.
Again because it analyzes very small samples, controlling contaminants is difficult.
However, the AMS method also has advantages.
Apart from archaeology and geology, AMS is also very useful in ocean sciences as well as biomedical research.
Also, unlike the radiometric method that requires large samples; a minimum of 10 grams. The AMS will work effectively with very little sample sizes, as little as 200 milligrams is enough sample to be analyzed effectively with the Accelerometer Mass Spectrometer dating method.
Radiocarbon dating is generally a destructive process; archaeologists first choice is the AMS technique because it prevents unwanted and unnecessary damage to samples since it only requires a very little sample for analyses.
The AMS technique makes dating even the smallest samples like blood particles possible.
The AMS dating method takes lesser time for sample analyses of carbon 14 content compared to the radiometric method, and it also yields more accurate results.
SERIATION DATING
This method also called artefact sequencing, is not an absolute way of dating like in the carbon dating techniques. In the seriation method of dating, objects and artefacts that are in close association with each other are placed in chronological order.
These are mostly artefacts obtained from different locations but are of the same or a similar culture.
This method is a relative way of dating and is employed in scenarios where more absolute dating methods can not be applied. It works because the style of objects change over time and will always change.
Assortment of clay pots that can be dated using seriation
Objects such as stone tools, pottery fragments, and other artefacts can be dated this way. It is an accepted standard of dating and has been known to be frequently used in Europe to reconstruct chronological sequences of graves in cemeteries.
The backbone of the seriation technique is in establishing a typology.
The task of forming or classifying a group of objects into the factions is extremely important. And errors here will result in an error in the dating.
To obtain a correct seriation result Doran and Hodson listed three conditions that must be met[1].
“Regional Variations must be kept to a minimum, The objects analyzed must all come from a single cultural tradition, and finally, the traits or attributes included in the seriation must depend on cultural aspects and not necessarily function.”
The seriation process, when done correctly, can also reveal some social information on the owners of the objects which is reflected by the designation of the corresponding set of objects.
The disadvantage of the seriation dating method is that it is not precise. Also, there is a greater tendency for erratic dating due to human error.
One good thing about the seriation technique is that it led to the typology method of dating.
STRATIGRAPHIC METHOD
This method bothers on geology. It is based on information gotten from the soil. The stratigraphic dating method heavily depends on the principle of the superposition of strata. The superposition of strata suggests that for layers of undisturbed soil, the upper horizons are newer and therefore later than the lower ones.
The stratigraphic process involves the excavation of soil either openly or in a box form and then the isolation of each stratum into separate chronological units, the units incorporate objects or artefacts. The oldest units are are the bottom while the newest ones are at the top.
The reliability of the stratigraphic method of dating depends on whether the soil or stratigraphic levels are undisturbed. If undisturbed, stratigraphic dating is very reliable.
The stratigraphic method can be used to date things like artefacts, weapons, jewellery, human remains, etc.
This dating technique provides more accurate data when combined with other dating methods. Sometimes its result is based on diagnostic artefacts that are found within the soil strata, like stone tools, pottery styles or objects whose age is known or adjudged to belong to a specific period such as coins. These kinds of objects if discovered at a site can be used to date the soil as well as link them to the object and events associated with such locations.
Stratigraphic dating might not be very reliable alone. This is because soil might have been disturbed at an earlier time and as such might produce inaccurate results.
This method of dating is not an absolute dating technique and as such do not provide exact dates.
TYPOLOGY DATING
The Typology dating method is derived from the serial method. This method compares objects, classifies them based on their similarity or dissimilarity and then goes ahead to link them to a specific period.
It is normally used when absolute dating methods cannot be implemented. With this method, archaeologists can quickly identify a period to which an object or even cultural sites belongs to.
Typology dating process involves a physical assessment of certain aspects of the object; its characteristics, architecture, and design. The object is then dated to a certain period in history.
As a general rule earlier objects are simpler while the later ones are more complex and elaborate.
It is used to date objects such as pottery, weapons, tools, projectile points, and ceramic vessels. These types of objects present several characteristics which are used for dating them. Characteristics like the decorative techniques, motifs and style as in ceramics. For stone tools, the morphology and raw materials are considered.
The advantage of this type of dating technique is that it allows for a clear observation of the development over time of many objects. It is also not a complex process and very cheap.
It, however, does not give an absolute age and like its predecessor seriation dating technique is easily prone to errors. Since it is subject to people’s opinions and does not necessarily present proof, this method is not very reliable.
MEMORY TOOLS
There are certain devices used by some African people to recount their history and past. These types of tools are not common and also require specialized knowledge for its effective use. Just as Europeans recorded history in books, to learn about their past, you read the books. That was the same way some African societies recorded history, although it was not written in books, it was rather recorded using a tool and was performed not read. While the European style of recording history has a static and chronological characteristic as is reflected on their written works, this African style follows a dynamic and oral narrative that reinforces the foundation upon which the ways or cultures of its people were established. And can also be used to interpret and judge contemporary situations.
The Lusaka Memory Board
A good example is the Lusaka Memory Board of the Luba Kingdom in the Democratic Republic of Congo. This special object is used by experts for the oral retelling of the history of the Luba people and their culture.
The memory board itself is made of different materials like wood, metal, and beads.
It is small enough to be comfortably held with one hand and is sought of hourglass shaped; the middle is slightly narrower, which makes for a more comfortable grip. On the surface, large beads are surrounded with smaller beads or lines of beads; the configuration contains different pieces of information like Royal names, myths and even narratives that recount the history of the Luba culture.
Despite its small size and simplistic form, this device is able to hold quite a lot of information, which when being retold, resonates with vividness and undistorted presentation just as its recorders intended.
It holds information like genealogy, location of things within the royal compound or tribal territory, court ceremony, clan migrations, cultural heroes and can even be used to map out the palaces of deceased rulers that are abandoned by new kings known to the people as “spirit capitals” to become receptacles of the former kings’ memory.
The process of using the board is highly narrative and performative; it involves singing and dancing.
The memory board serves as a mnemonic device. The experts or masters that posesses the knowledge and skill required to use the device are the elite members of the Mbudye Society. They are considered by the people as men of memory.
The user touches and feels the beads, shells and pegs recounting history as he does so.
He can also employ his skill using the memory board to resolve culture-related problems by recalling the established cultures of their ancestors held by the board.
SOURCES
- Michel Cagné. Dating In Archaeology. Published By The Canadian Encyclopedia. Jan 23, 2013. https://www.thecanadianencyclopedia.ca/en/article/dating-in-archaeology
FOOTNOTE
- Doran, J.E. and F.R. Hodson (1975). ↑
