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Encyclopedia > Glottochronology

Glottochronology refers to methods in historical linguistics used to estimate the time at which languages diverged, based on the assumption that the basic (core) vocabulary of a language changes at a constant average rate. This assumption, originally put forward by Morris Swadesh, is based on an analogy with the use of carbon dating for measuring the age of organic materials, in that a "lexical half-life" is estimated. The method estimates the length of time since two or more languages diverged from a common earlier proto-language, by counting the number of words that have been replaced in each language. This then yields an estimated date of origin for those languages. Glottochronology is an adjunct to lexicostatistics, with which it has been sometimes confused. Historical linguistics (also diachronic linguistics or comparative linguistics) is primarily the study of the ways in which languages change over time. ... Morris Swadesh (January 22, 1909 - July 20, 1967) was an American linguist. ... Radiocarbon dating is the use of the naturally occurring isotope of carbon-14 in radiometric dating to determine the age of organic materials, up to ca. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... Proto-language may refer to either: a language that is the common ancestor of a set of related languages (a language family), or a system of communication during a stage in glottogony that may not yet be properly called a language. ... In linguistics, the technique of glottochronology is used to estimate the time of divergence of two related languages. ...



The concept of language change is old and its history is reviewed in Hymes (1973) and Wells (1973). Glottochronology itself dates back to the mid-20th century (see Lees 1953; Swadesh 1955, 1972) An introduction to the subject is given in Embleton (1986) and in McMahon and McMahon (2005).

Glottochronology has long been controversial, partly owing to issues of precision, as well as the question of whether its basis is sound (see e.g. Bergsland 1958; Bergsland and Vogt 1962; Fodor 1961; Chretien 1962; Guy 1980). These concerns have been addressed by Dobson et al (1972), Dyen (1973) and Krustal, Dyen and Black (1973). The assumption of a single-word replacement rate can distort the divergence-time estimate when borrowed words are included; but more realistic models have been used.

Chretien purported to disprove the mathematics of the model. At a conference at Yale in 1971 his criticisms were shown to be invalid.

An fair overview of recent arguments can be obtained from the papers of a conference held at the McDonald Institute in 2000. See Renfrew, McMahon and Trask, 2002. These presentations vary from "Why linguists dont do dates" to the one by Starostin discussed above.


Word list

The original method presumed that the core vocabulary of a language is replaced at a constant (or near constant) rate across all languages and cultures, and can therefore be used to measure the passage of time. The process makes use of a list of lexical terms compiled by Morris Swadesh assumed to be resistant against borrowing (originally designed as a list of 200 items; however, the refined 100 word list in Swadesh (1955) is much more common among modern day linguists). This core vocabulary was designed to encompass concepts common to every human language (such as personal pronouns, body parts, heavenly bodies, verbs of basic actions, numerals 'one' and 'two', etc.), eliminating concepts that are specific to a particular culture or time. It has been found that this ideal is not in fact possible and that the meaning set may need to be tailored to the languages being compared.

The percentage of cognates (words that have a common origin) in these word lists is then measured. The larger the percentage of cognates, the more recently the two languages being compared are presumed to have separated. This does not adequately cite its references or sources. ...

Glottochronologic constant

Lees obtained a value for the "glottochronological constant" of words by considering the known changes in 13 pairs of languages using the 200 word list. He obtained a value of 0.806 +/-0.0176 with 90% confidence. For the 100 word list Swadesh obtained a value of 0.86, the higher value reflecting the elimination of borrowed words. This constant may be related to the retention rate of words by:-

L = 2ln(r)

where L is the rate of replacement, ln is the logarithm to base e, and r is the glottochronological constant

Divergence Time

The basic formula of glottochronology in its shortest form is:-

t = frac{ln(c)}{-L}

where t = a given period of time from one stage of the language to another, c = proportion of wordlist items retained at the end of that period, and L = rate of replacement for that word list.

By testing historically verifiable cases where we have knowledge of t through non-linguistic data (e. g. the approximate distance from Classical Latin to modern Romance languages), Swadesh arrived at the empirical value of approximately 0.14 for L (meaning that the rate of replacement constitutes around 14 words from the 100-wordlist per millennium).


Glottochronology is hold by its proponents to work in the case of Indo-European, accounting for 87% of the variance.[citation needed] It is also said to work for Hamito-Semitic (Fleming 1973), Chinese (Munro 1978) and Amerind (Stark 1973; Baumhoff and Olmsted 1963). For the latter correlations have been obtained with radiocarbon dating and blood groups as well as archaeology.

Attempts to improve Swadesh's model

Older attempts

Various improvements have been made to Swadesh's simple model. Inhomogeneities in the replacement rate were dealt with by Van der Merwe (1966) by spliting the word list into classes each with their own rate. While Dyen, James and Cole (1967) allowed each meaning to have its own rate. Simultaneous estimation of divergence time and replacement rate was studied by Krustal, Dyen and Black.

Brainard (1970) allowed for chance cognation and drift effects was introduced by Gleason (1959). Sankoff (1973) suggested introducing a borrowing parameter and allowed synonyms.

A combination of these various improvements is given in Sankoff's "Fully Parameterised Lexicostatistics". In 1972 Sankoff in a biological context had developed a model of genetic divergence of populations. Embleton (1981) derives a simplified version of this in a linguistic context. She carries out a number of simulations using this which are shown to give good results.

Starostin's method

Somewhere in between the original concept of Swadesh and the rejection of glottochronology in its entirety lies the idea that glottochronology as a formal method of linguistic analysis becomes valid with the help of several important modifications. In particular, an attempt to introduce such modifications was performed by the Russian linguist Sergei Starostin, who had proposed that Dr. Sergei Anatolyevich Starostin (b. ...

  • systematic loanwords, borrowed from one language into another, are a disruptive factor and have to be eliminated from the calculations; the one thing that really matters is the "native" replacement of items by items from the same language. The failure to notice this factor was a major reason in Swadesh's original estimation of the replacement rate at under 14 words from the 100-wordlist per millennium, when the real rate is, in fact, much slower (around 5 or 6). Introducing this correction effectively cancels out the "Bergsland & Vogt" argument, since a thorough analysis of the Riksmal data shows that its basic wordlist includes about 15-16 borrowings from other Germanic languages (mostly Danish) - exclusion of these elements from the calculations brings the rate down to the expected rate of 5-6 "native" replacements per millennium;
  • the rate of change is not really constant, but actually depends on the time period during which the word has existed in the language (i. e. chances of lexeme X being replaced by lexeme Y increase in direct proportion to the time elapsed – the so called "aging of words", empirically understood as gradual "erosion" of the word's primary meaning under the weight of acquired secondary ones);
  • individual items on the 100 wordlist have different stability rates (for instance, the word "I" generally has a much lower chance of being replaced than the word "yellow", etc.).

The resulting formula, taking into account both the time dependence and the individual stability quotients, looks as follows: A loanword (or loan word) is a word directly taken into one language from another with little or no translation. ...

t = sqrt frac{ln(c)}{-Lc}

In this formula, -Lc reflects the gradual slowing down of the replacement process due to different individual rates (the less stable elements are the first and the quickest to be replaced), whereas the square root represents the reverse trend - acceleration of replacement as items in the original wordlist "age" and become more prone to shifting their meaning. The formula is obviously more complicated than Swadesh's original one, but, as shown in Starostin's work, yields more credible results than the former (and more or less agrees with all the cases of language separation that can be confirmed by historical knowledge). On the other hand, it shows that glottochronology can really only be used as a serious scientific tool on language families the historical phonology of which has been meticulously elaborated (at least to the point of being able to clearly distinguish between cognates and loanwords).


Today, glottochronology is generally rejected by historical linguists (one representative example is Crowley 1997:171ff), for the following objections:

Different "rates"

From the beginning, criticism has mainly been based on many counterexamples, which yielded varied changes in time.

Representatives for this line of arguments are Bergsland & Vogt (1962), or Tischler (1973). Thus, Bergsland & Vogt made an impressive demonstration, on the basis of actual language data verifiable by extra-linguistic sources, that the "rate of change" for Icelandic constituted around 4% per millennium, whereas for Riksmal (Literary Norwegian) it would amount to as much as 20%. (Swadesh's proposed "constant rate" was supposed to be around 14% per millennium). Norwegian is a Germanic language spoken in Norway. ...

Moreover, it is highly likely that the chance of replacement is in fact different for every word or feature ("each word has its own history"). Frequency of usage might play a major role here (cf. Zipf 1965).

No stable region of concepts

Another line of arguments is represented by Haarmann (e.g. 1990), who demonstrated that there is no region of the vocabulary "safe" from being changed, as has been argued by glottochronologists, e.g. parts of the body, colour terms, numbers, or pronouns.

Socio-historical reasons are uncomputable

A newer argument is that language change arises from socio-historical events which are unforeseeable and uncomputable, and which do not affect language at a constant rate (cf. Holm 2007). For example, English did not replace about50 % of its originally Germanic vocabulary 'by time', but by Norman dominance after the battle of Hastings, besides a long-lasting educational background of Latin. Though this event changed only one or two percent of "the" (depends on the version) Swadesh 100-wordlist, there are six items changed already before by Viking influence. Please note that this is a difference in quantity, not in reasons and computability. Combatants Normans supported by: Bretons, Aquitanians, Flemings Anglo-Saxons Commanders William of Normandy, Odo of Bayeux Harold Godwinson † Strength 7,000-8,000 7,000-8,000 Casualties Unknown, thought to be around 2,000 killed and wounded Unknown, but significantly more than the Normans The Battle of Hastings was...

Another example is Albanian, which changed 90% of its Indo-European heritage, and still about 75% in the Swadesh list, mainly by Roman dominance, later by South-Slavonian influence.


  • Arndt, Walter W. (1959). The performance of glottochronology in Germanic. Language, 35, 180-192.
  • Bergsland, Knut; & Vogt, Hans. (1962). On the validity of glottochronology. Current Anthropology, 3, 115-153.
  • Brainerd, Barron (1970). A Stochastic Process related to Language Change. Journal of Applied Probability 7, 69-78.
  • Callaghan, Catherine A. (1991). Utian and the Swadesh list. In J. E. Redden (Ed.), Papers for the American Indian language conference, held at the University of California, Santa Cruz, July and August, 1991 (pp. 218-237). Occasional papers on linguistics (No. 16). Carbondale: Department of Linguistics, Southern Illinois University.
  • Campbell, Lyle. (1998). Historical Linguistics; An Introduction [Chapter 6.5]. Edinburgh: Edinburgh University Press. ISBN 0-7486-0775-7.
  • Chretien, Douglas (1962). The Mathematical Models of Glottochronology. Language 38, 11-37.
  • Crowley, Terry (1997). An introduction to historical linguistics. 3rd ed. Auckland: Oxford Univ.Press. pp171-193.
  • Gudschinsky, Sarah. (1956). The ABC's of lexicostatistics (glottochronology). Word, 12, 175-210.
  • Gleason, H (1959). Counting and Calculating for Historical Reconstruction. Anthropological Linguistics 1, 22-32.
  • Haarmann, Harald. (1990). Basic vocabulary and language contacts; the disillusion of glottochronology. Indogermanische Forschungen 95:7ff.
  • Hockett, Charles F. (1958). A course in modern linguistics (Chap. 6). New York: Macmillan.
  • Hoijer, Harry. (1956). Lexicostatistics: A critique. Language, 32, 49-60.
  • Holm, Hans J. (2007 in print). The new Arboretum of Indo-European 'Trees'; Can new algorithms reveal the Phylogeny and even Prehistory of IE?. The Journal of Quantitative Linguistics 14-2.
  • Hymes, Dell H. (1960). Lexicostatistics so far. Current Anthropology, 1 (1), 3-44.
  • Lees, Robert. (1953). The basis of glottochronology. Language, 29 (2), 113-127.
  • McWhorter, John. (2001). The power of Babel. New York: Freeman. ISBN.
  • McMahon, April and McMahon, Robert (2005) Language Classification by Numbers. Oxford: Oxford University Press (in particular p. 95).
  • Nettle, Daniel. (1999). Linguistic diversity of the Americas can be reconciled with a recent colonization. in PNAS 96(6):3325-9.
  • Renfrew,C., McMahon, A., & L. Trask, Eds. (2000). Time Depth in Historical LInguistics. Cambridge, England: The McDonald Institute for Archaeological Research.
  • Sankoff, David (1972). Reconstructing the History and Geography of an Evolutionary Tree. American Mathematical Monthly 79, 596-603.
  • Sankoff, David (1973). Mathematical Developments in Lexicostatistic Theory in Current Trends in Linguistics, Ed T Sebock V11, 93-113.
  • Sjoberg, Andree; & Sjoberg, Gideon. (1956). Problems in glottochronology. American Anthropologist, 58 (2), 296-308.
  • Starostin, Sergei. Methodology Of Long-Range Comparison. 2002. [1]
  • Swadesh, Morris. (1955). Towards greater accuracy in lexicostatistic dating. International Journal of American Linguistics, 21, 121-137.
  • Swadesh, Morris (1972). What is glottochronology? In M. Swadesh, The origin and diversification of languages (pp. 271–284). London: Routledge & Kegan Paul.
  • Tischler, Johann, 1973. Glottochronologie und Lexikostatistik [Innsbrucker Beiträge zur Sprachwissenschaft 11]; Innsbruck.
  • Zipf, George K. (1965). The Psychobiology of Language: an Introduction to Dynamic Philology. Cambridge, MA: M.I.T.Press.

John H. McWhorter (1965- ), African American, was associate professor of linguistics at University of California, Berkeley until 2003, and is now a Senior Fellow at the Manhattan Institute think tank. ...

External links

  Results from FactBites:
glottochronology Information Center - glottochronology (286 words)
Glottochronology was a linguistics method used to estimate the time of divergence of two related languages.
The glottochronology method presumes that the core vocabulary of a language is replaced at a constant (or near constant) rate, and therefore can be used to measure the passage of time.
Glottochronology is no longer considered a valid technique by mainstream linguists, because there is no evidence to support the assumption that language change occurs at a steady rate, and much evidence to support the idea that languages change alternately very slowly and very quickly.
Glottochronology at AllExperts (776 words)
This assumption, originally put forward by Morris Swadesh, was based on an analogy with the use of C14 dating for measuring the age of organic materials, in that a "lexical half-life" is estimated and used to extrapolate to the point in time at which the languages in question diverged from a common proto-language.
Glottochronology is rejected by mainstream linguists, who view it as having been falsified by many counterexamples.
On the other hand, it shows that glottochronology can really only be used as a serious tool on language families the historical phonology of which has been meticulously elaborated (at least to the point of being able to clearly distinguish between cognates and loanwords).
  More results at FactBites »



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