Word-pedigree: The method of radioactive dating in linguistics

Good day, dear Take in Mind readers! As humanity plunges deeper into the boundless expanses of scientific knowledge, the knowledge becomes specialized more and more. The times of Leonardo da Vinci and Lomonosov (when an educated person was an expert in medicine, jurisprudence, natural sciences, architecture, and philology at the same time) have long sunk into oblivion. I wanted to write “Unfortunately” or “Fortunately”, but, I think, neither one nor the other is quite true.

Yes, with very few exceptions, the ocean of knowledge does not allow scientists to truly delve into other areas, which are out of their direct expertise. But, on the other hand, the most interesting ideas (and sometimes even revolutionary discoveries), most of the time, appeared from a joint work of scientists from completely different fields. Another case is ideas that were “borrowed” by some unique genius, that converted them from one field of knowledge into another.

Here is a nice example:

For a long time, the dating of the emergence of a new language was carried out either based on historical data or approximately using a rough estimation, by eye. In the early 1950s, the American linguist Maurice Swadesh (1909-1967) proposed a completely new method of comparative historical linguistics (both unexpected and brilliant), lexicostatistics (also known as glottochronology): Comparing a set of words that are presented in all languages ​​(so-called lexical cognates).

The scientist proposed a simple method of mathematical calculation to determine when languages had ​​separated from a common “progenitor” and each other. Logically, a genealogical classification of languages can be performed based on this method​.

Photo of Maurice Swadesh. Fair use.

Where did the idea come from? Swadesh adapted to linguistics the method of… radiocarbon dating, proposed by American physical chemist, 1960 Nobel prize laureate Willard Frank Libby (1908 –1980) just a few years earlier! As you probably know, the method is based on the fact that radiocarbon (14C) is constantly being created in the Earth’s atmosphere by the interaction of cosmic rays with atmospheric nitrogen, and living organisms absorb together with food both non-radioactive (12C) and radioactive (14C) carbon. During the life of an organism, the percentage of the isotope remains stable, and when the organism dies, 14C can’t enter the tissues anymore, but only decays, turning into nitrogen. Therefore, the time of an organism’s death can be estimated from 14C decay.

The decay equation is:

N=N0*e– λt

Where N is the content of radioactive atoms in time of the examination, N0 is the isotopes’ content at time 0, and λ is the decay constant (for example, it is 8267 years for 14C). Therefore, we can rewrite the 14C equation as following:

t=ln(N0/N)*8267

It is assumed that the sample initially had the same 14C/12C ratio as in the atmosphere, and since the size of the sample is known, it is easy to calculate the number N0, and, correspondently, the sample’s age.

In analogy with the radiocarbon dating, Swadesh proposed that if t is the time since two related languages diverged from each other and C is the proportion of items on a basic vocabulary list that are cognate between the two languages, then the time can be estimated as:

t = ln C / 2 ln r

Where r is the average proportion of items on the list of lexical cognates that are retained after a standard time period (usually 1000 years). 

The minimal set of the lexical cognates is contained in a 100-word Swadesh list. The less semantically stable, but more detailed 207-word list is also in general use. If we compare an arbitrary pair of Slavic languages ​​(for example, Russian-Polish or Czech-Serbian), it turns out that the percent similarity for the lexical cognates in the Swadesh list is around 80%. For a pair of either Slavic language with a language of the Baltic group (e.g., Russian vs. Lithuanian), the coincidence will be 45-50%, and for a Slavic language with one of the Germanic languages ​​- about 30%.

If we accept another Swadesh assumption that the rate of loss of words from the basic vocabulary is constant, then knowing the percentage of common words in two related languages allows calculating the date of their divergence from the ancestor language.

Let’s say few words about the principle on the basis of which Swadesh and his colleagues chose words for their lists (we don’t want to waste your time listing even the short 100-word list – please enter “Swadesh List” into any search engine and in a second you will have the list in any language). The lexical cognates usually include words that do not depend on a specific culture and historical epoch and are present in any language. It includes the names of the most elementary and universal phenomena of nature and natural objects, twelve body parts, numerals (at least the first few), simple actions, and signs. In other words, in order to create a universal list, strict independence should be kept both from the epoch, the place of residence, and the technical and cultural progress.

In addition, Swadesh did not include any names for tools or weapons in his list. For the same reason, only “bird”, “fish”, “dog” and “louse” were included for animals. Another example is numerals. Only two (“one” and “two”, respectively) were included into the 100-word list. Words describing people (“person”, “man”, ” female”) and human body parts (such as “belly”, “blood”, “bone”, “ear”, “eye”, “fat”, “leg”, “hair”, “arm”, “head”, “heart”, “tongue”, “tooth” etc.) are also associated with the idea of ​​universality.

Naturally, there were (and are) many questions about the method, and clearly, additional analysis, correction, and discussion have been required. But such is the fate of the discoverer: using a non-standard approach for the humanities, Swadesh opened the linguistic Pandora box. More than 60 years after the pioneering publications, many scientists around the planet continue to develop lexicostatistics. For those who want to go deeper, in addition to the authors cited below, we suggest reading the works of Gudschinsky, Dyen, Dolgopolsky, and others.

Finally, we want to suggest a little lifehack for our readers. We hope that very soon we all will have an opportunity to travel again. We suggest using the scientific achievements for practical purposes, and before your voyage, learn 100 (or 207) words of the Swadesh list in the language of the place of your future visit. That will allow you to completely blend in with the local culture without broken English or funny gestures.


References:

Swadesh, Morris. (1952). Lexicostatistic dating of prehistoric ethnic contacts. Proceedings American Philosophical Society, 96, 452-463.

Swadesh, Morris (1955). Towards greater accuracy in lexicostatistic dating. International Journal of American Linguistics, 21, 121-137.

Gudschinsky S. The ABCs of lexicostatistics (glottochronology), Word,12:612 (1956) 

Старостин С. А. Труды по языкознанию. Языки славянских культур, 2007. – С. 407-447

Саенко М.Н. “Общие инновации в базисной лексике как аргумент в дискуссии о балто-славянском единстве.” Диссертация, Южный Федеральный Университет, 2014


Featured image by Skylar Kang from Pexels.


Related Articles:

Facebook Comments