One of the most important aspects of paleontology, is the ability to place things on a timeline, or a map of existence. Knowing when and where something came from, is critical to understanding its place and role in the natural world. Being able to know when something lived, and when it dates to is critical to Paleoanthropology, and our understanding of Human Origins.
There are many techniques that can be used to date organic objects, as well as non-organic. And depending on what the material is, and how old it is believed to be, specific methods are used. For example, one of the most famous dating methods is Carbon-14 dating. We are not going to go into the details of how this works (perhaps another article?) But I will tell you, that Carbon dating only works to about 55,000 years ago. Meaning anything older than that will not be calculated correctly, or give any information really on what you are trying to ascertain.
So, because of this problem, and the fact that the vast majority of hominin history was prior to 55kya, other methods that can date farther back in time are necessary. The first time that one of these methods was used, Potassium Argon dating, in Olduvai Gorge, was done by Louis Leakey et al., 1961. Many types of dating have been previously applied to Olduvai, Radio Carbon (Leakey et al., 1972) electron spin resonance (Skinner et al., 2003) uranium series (Seitz and Taylor, 1974) Tephrostratigraphy (mchenry, 2012; mchenry et al., 2016) paleomagnetism (Tamara et al., 1995: deino et al., 2021) and primarily potassium argon dating (k/Ar) and argon argon (mangea 1993; deinonychus 2012).
This is all very critical, and it is important to understand that many of these methods, especially those that are not performed on organic material, such as rocks, volcanic tuffs etc. We, up until recently could not get a clear picture of the date of say, a stone tool, because we had to get the dates from the surrounding sediments and items. But say those were not there? Then what do you do?
At the T69 complex, in the Frida Leakey Korongo (FLK) west gully, led by Toshi Fujioka and Alfonso Benito-Calvo, we find Bed II of this particular volcanic tuff, while Bed I was covered with volcanic material and easily datable, Tuff Two and Three were near impossible, and this is of course where the stone tool assemblages were discovered. While this is a destructive method of dating (meaning part of the material is destroyed in obtaining its date), with the size of certain assemblages, this is less of a problem than it used to be.
“Secondly the significance of cosmogenic nuclide isochron burial dating lies in its ability to be applied directly to stone tools:cosmogenic nuclide exposure during dating and simple burial dating for the archaeological assemblage itself, rather than estimates based on underlying or overlying sediments, as is the case for Ar/Ar dating of tuffs.” So, now that we can date stone tool assemblages themselves, and not just the sediments around them, we can get a much more clear and accurate date.
Some may ask, how do we know if it is accurate, and the answer to that, is the dates are congruent with other dating methods that were used previously to determine the ages of the tuffs and stone tool assemblages. One catch however, is that the items must have a high content of quartzite to analyze. Without this, the method simply does not function the same.
With this new dating technology, if the assemblages are large enough, and meet the proper requirements, we are now able to get much more accurate dates for specific stone tools, rather than the earth and land around them. This has the potential to be very beneficial in the study of lithic (stone tools) and their use in early human origins.
Sources:
- Published in the Journal for Human Evolution by Toshiyuki Fujioka, Alfonso Benito-Calvo, Rafael Mora, Lindsay McHenry, Jackson. Njau, Ignacio de la Torre- https://www.sciencedirect.com/science/article/pii/S004724842200015X
2. Leakey et al., 1972
3. Skinner et al., 2003
4. Seitz and Taylor, 1974
5. Mchenry, 2012; Mchenry et al., 2016
6. Tamara et al., 1995:
7. Deino et al., 2021
8. Mangea, 1993
9. Deinonychus, 2012
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