Ceramics dated for stubborn fat

Chemists have found a way to apply radiocarbon analysis for Dating of archaeological ceramics. They used the grease embedded in the walls of blood vessels when cooking. Obtained by the new method of Dating several findings coincided with the dates obtained by traditional methods. In addition, scientists were able to date the find, which was impossible to date by other methods. The article describing the method published in the journal Nature.

Shards of pottery — a common finding of archaeologists. Clay can be found almost everywhere where people live, and they are very early and almost universally mastered the technology of manufacturing of its cookware. In addition, fired clay is very well preserved in any soil. Often the style of pottery is the main characteristic that classified archaeological cultures (e.g., Neolithic culture of pit-comb, linear-tape and stroke-ornamented pottery). Tracing the evolution of forms of vessels and patterns on them, it is possible to establish the relative chronology of their creation. However, the absolute Dating of ceramics is very difficult.

Radiocarbon analysis is one of the most common methods of absolute Dating of modern archaeology. It applies to substances of organic origin such as bone, fabric and wood. In the atmosphere and in any body carbon represented mainly by stable isotopes, but there is also the radioactive isotope carbon-14. While the body is alive and participates in the carbon exchange (e.g., breathing or photosynthesise), the content of carbon-14 remains the same as in the atmosphere. The relation of its content to the content of stable isotopes is known. When an organism dies, the isotopes remain stable, and carbon-14, like every radioactive isotope decays at a known rate (its half — life of 5700 ± 30 years). Knowing the ratio of stable isotopes carbon-14 in the sample of organic matter and comparing it with the ratio in the atmosphere, you can determine how long ago death of the body. This is usually the method of mass spectrometry: the sample is burned in a special chamber, and its isotopic composition is determined by the resulting ions.

Clay is an organic material, and therefore radiocarbon Dating is not applicable to it. Ceramics tend to date other objects found with it. For example, if the burial the bones and pottery shards, bones can be dated to the same radiocarbon method, and the shards to refer to the same time.

When cooking food on the fire in a clay vessel small quantities of vegetable and animal fats eats into the walls and stored together with ceramics. Group Richard Evershed (Richard Evershed), head of the Center for biochemical studies of the University of Bristol, found a way to remove these organic residues from ceramics.

The analyzed shards they are exposed to sulfuric acid. The resulting material was consistently divided into phases in the centrifuge and then into the chromatograph. As a result, they first identified fats embedded in the ceramic, and then from them — palmitic and stearic acids in sufficient quantities for mass spectrometry.

To check the accuracy of the method, the Evershed and his colleagues studied a total of 27 samples of ceramics from ten archaeological sites dated by other methods. Among them were two vessels, found at the Sweet Track Neolithic unmade road with a wooden bridge in the South-West of England; and four from Chatal-Chuuka in southern Turkey; as well as samples from the Sahara, Poland and several sites in France, Germany and the Netherlands. In all cases, the dates obtained fit into chronological models of monuments constructed on the basis of Bayesian statistics , according to conventional radiocarbon Dating, dendrochronology (Dating the growth rings of trees) and other methods.

In addition, the group Evershed examined four shard from a large number of the Neolithic period, discovered during the construction of an office center in London. Stones, bones and charred plant remains, found together with ceramics, was damaged, and therefore find it impossible to date.

A new method shards dated 4911 ± 27 years before present, 4742 ± 22 years to date, 4652 ± 26 years to date, 4733 ± 22 years up to the present time (“present” is conventionally taken 1950), which coincides with the Dating of the stylistically similar vessels found in southern England. Thus, the method allowed us to date the discovery of ceramics in the absence of other datable materials.

Chemists are constantly finding ways to extend the use of radiocarbon Dating. So, in 2018, French scientists managed to date using the radiocarbon method, the carbonate of lead — oxide inorganic component used, particularly in ancient Egyptian and ancient Greek cosmetics. Radiocarbon analysis of inorganic substances has been possible due to the fact that lead carbonate reacts with atmospheric carbon.

Artem Efimov

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