Wed. Sep 28th, 2022

Indiscrete isotopes betray the origin of ancient people

In answering the most common question in archaeology – about the origin of humans – an increasingly popular method, based on the study of strontium isotopes, is helpful. "We are what we eat" – This is how prof. Zdzislaw Belka of the Isotope Laboratory at the Adam Mickiewicz University in Poznan, Poland. A. Mickiewicz University in Poznan.

Isotopes are nothing more than rótive varieties of one element, whichóre contain an equal number of protonów, but róThey differ in the number of neutronów. Many elementsóin has a few each, and someóre – even after a dozen or so isotopeów. In nature, elements usually occur as mixtures of them.

This is the case, for example. In the case of strontium, którego the two isotopes numbered 86 and 87, whichóre in turn mean their mass, i.e. the sum of the number of protonsów and neutronów. – The ratio of strontium 87 to strontium 86 in the rocks was established at the time of their formation in the Earth’s crust, explains Prof. Watson in an interview with PAP. Zdzislaw Belka of the Isotope Laboratory of the Adam Mickiewicz University in Poznan, Poland. A. Mickiewicz University in Poznan. – The ratio depends on the age and type of rock. Vegetation growing in a particular place takes over the isotopic ratio ofóin strontium that is in the local substrate. Herbivores acquire strontium isotopic ratios from plants they eat and water they drink. Similarly, carnivorous animals and humans acquire the isotopic ratio of strontium from the food they eat.

That’s why isotope testing has become a convenient tool, after which theóre eagerly reached by archaeologists during the róThe study of the origin and migration of the population. – In the case of the method "strontium" Indeed, it is accurate to say that "we are what we eat" – expert notes.

As scientists have more and more data on. strontium isotopic composition in róof different elements of the local environment, measurements of these isotopesóin the bones and teeth of ancient people make it possible to tell whether the dead came from the region where they were buried – or whether they came from a different area, characterized by a different isotopic composition.

Mysteries of the origin of humans are being clarified with the support of geochemistsóin, whichórzy – oprócz bones, they usually examine the enamel of the toothów and check the isotop ratio in itóin strontium 87 and 86. The results obtained poróThey then correlate with the proportions of the same isotopesóin the local environment, in plants, soil and rocks. In this wayób check whether the isotopic ratioów of strontium in the remains of a given individual are identical to those in the local environment, or not.

Mówishing to use the isotopeóin strontium prof. Belka cites an interesting example of research by an archaeologistów, któThe próThey were able to establish the origin of the Viking warriorsów, stationed for a long time in Denmark, near Copenhagen. It turned out that they were mostly from Norway and the area of theóInhabited by Slavic peoples.

Another example comes from Poland, from a 17th-18th century cemetery in Drawsko nad Notcią, in którym someóre persons were buried in the mannerób characteristic of osób suspected of drinking blood – vampireów. Recently, archaeologists wanted to find out whether locals were buried in them, or whether they were aliens, and were therefore stigmatized as alleged vampires. Isotope studiesóIn the strontium cemetery, they showed that although the Drawsko cemetery buried róalso migrantów, are all pochówki „vampireów” pertained to osób, whichóre born in this area.

Próbki isotope for the studyóIn strontium, geochemists usually take from tooth enamelów. This is the best material for analysis, as the mineral that builds it is very stable and only forms until the teeth are fully formedów (as opposed to bones, whichóre change throughout a person’s life). By examining the ratio of strontium 87 to strontium 86 in the enamel, experts are confident that they are gaining information from a well-defined stage of the deceased person’s life – its childhood or early youth.

As the professor notes, the method „strontowa” works well in studying the migration of ancient societies, whichórych members fed exclusively on local products, and not – imported from far away (as happens today). Its use thus makes sense primarily in the study of populations living several hundred years ago and earlier, including – in the prehistoric period. In their case, the proportion of isotopeóIn fact, the proportion of strontium supplied to the body with food was the same as the proportion of these isotopesóin the local environment.

Prof. Belka points out that scientists are now able to measure isotope ratiosóin strontium in the materials and tissues studied to the nearest one-thousandth of a percent. This is much more accurate than the precision required for archaeological research, thus avoiding the problems ofów associated with ew. Statistical measurement errors. – We have nó¿, whichóry is much sharper than the one we need to make the cut. But perhaps in the future we will be able to use the precision of this method in próbie answers to other questions,” suggests the UAM scientist.

Using the method „strontium” In archaeology, it is crucial to know the natural "background", or isotope ratio knowledgeóin strontium in the local environment,” stresses Professor. A few years ago Poland was a white spot in this respect. This, however, is rapidly changing, m.in. thanks to a project carried out with the support of the National Science Center. As a result, scientists were able to learn the strontium isotopic composition of rivers, vegetation and substrate from the entire Oder River basin and western Pomerania (i.e., from approx. 40 percent. surface of the country).

Thanks to the studies conducted, it is now known that in terms of strontium isotopic composition, the area of Poland póof the northern and central region, covered by glacial deposits, clearly róterrain changesóin southern Poland. Therefore, it is very easy to odró¿nish people whoóre born in Kuyavia, Pomerania, or Masuria – from those whoóre originated in Lesser Poland or Silesia,” notes Prof. Belle.

Method „strontium”, like any research method, however, has limitations – notes the scientist. Although today we are able to make precise isotopic measurements of theóin strontium, then not every result allows for a clear archaeological interpretation. Indeed, many sites are characterized by a very similar or nearly identical isotopic composition of strontium. Therefore, the isotopes of strontium do not allow odróżnić osób, whichóre came from e.g. From the vicinity of Poznań, from those whoóre born in Kuyavia.