Linguistic relatedness is defined by shared ancestry, not by synchronically measured distance. Of course (some) distance metrics may be correlated with the degree of relatedness, since the older the last common ancestor of languages A and B, the more independent innovations are likely to have accumulated in either lineage over time, increasing the difference between them -- although it has to be kept in mind that the rate at which innovations arise and get fixed is anything but uniform. There is, however, no simple algorithm for computing the structure of the family tree, given just the measured distances.

Note, by the way, that:

Every method has its limit of reasonable application. Even for "unrelated" languages measurements of "distance" (no matter how defined) are certain to yield some values, which will however be random noise, not genetic information. They will not tell us whether English is more closely related to Tongan or to Quechua, or whether Quechua and Tongan cluster together to the exclusion of English. 

Have a look at the genetic literature, and the constructed evolutionary branching tree for world languages. Check for genetic distances.

Warning:   The papers are not linguist-friendly.

Linguistic relatedness is defined by shared ancestry, not by synchronically measured distance. Of course (some) distance metrics may be correlated with the degree of relatedness, since the older the last common ancestor of languages A and B, the more independent innovations are likely to have accumulated in either lineage over time, increasing the difference between them -- although it has to be kept in mind that the rate at which innovations arise and get fixed is anything but uniform. There is, however, no simple algorithm for computing the structure of the family tree, given just the measured distances.

Note, by the way, that:

Every method has its limit of reasonable application. Even for "unrelated" languages measurements of "distance" (no matter how defined) are certain to yield some values, which will however be random noise, not genetic information. They will not tell us whether English is more closely related to Tongan or to Quechua, or whether Quechua and Tongan cluster together to the exclusion of English. 

Thank you both so much for the most helpful responses.

Prof. Gasiorowski, yes, I realize that measuring linguistic distance is extremely complex and that ancestry is crucial. 

 P.S. 

I did not make it clear enough what I meant by the percentiles I provided: they represent percentage of world population speaking the languages (based on Rubenstein 2014, The Cultural Landscape: An Introduction to Human Geography). 

Well, you wrote "about 50% of the world's languages", which suggests counting languages, not speakers. It should be corrected to "spoken by about 50% of the world's population". Accuracy is especially important when we write for lay readers.

These percentages are tricky, by the way, since a large proportion of mankind is at least bilingual, so the percentages for individual languages will add up to much more than 100%.

I hope you don't mind if we switch to first-name terms.

Absolutely. Thank you for the correction.

If you do not mind, I will send you an email and ask for your further advice on the topic.  

I will be delighted to switch to first-name terms with you.

Monika

Hello Monika,

One of the methods for classifying words based on linguistic distance may be the application of  language typology designed in terms of morphological behavior of  words in different languages. According to this classification, all languages may be classified into isolating, agglutinating, synthetic, incorporating and infixing language types. As an illustration, in contour languages like Chinese each morph represents a word, whereas in incorporating languages such as the one used by  Eskimos, a full sentence represents a word. For further information, please read the book  titled " Understanding Morphology" by Francis Katamba. 

Best regards,

R. Biria

Hi Reza,

Thank you very much for the response as well as the title of the book.

All the best,

Monika

Evolutionary dynamics of language systems

Abstract

Understanding how and why language subsystems differ in their evolutionary dynamics is a fundamental question for historical and comparative linguistics. One key dynamic is the rate of language change. While it is commonly thought that the rapid rate of change hampers the reconstruction of deep language relationships beyond 6,000–10,000 y, there are suggestions that grammatical structures might retain more signal over time than other subsystems, such as basic vocabulary. In this study, we use a Dirichlet process mixture model to infer the rates of change in lexical and grammatical data from 81 Austronesian languages. We show that, on average, most grammatical features actually change faster than items of basic vocabulary. The grammatical data show less schismogenesis, higher rates of homoplasy, and more bursts of contact-induced change than the basic vocabulary data. However, there is a core of grammatical and lexical features that are highly stable. These findings suggest that different subsystems of language have differing dynamics and that careful, nuanced models of language change will be needed to extract deeper signal from the noise of parallel evolution, areal readaptation, and contact.

needed to extract deeper signal from the noise of parallel evolution, areal readaptation, and contact.

Thanks so much for sharing, Anthony.

Cheers,

Monika

Hi Monika,

As Piotr mentioned, obtaining distances between languages that reflect shared ancestry to a reasonable degree is not necessarily straightforward, for a number of reasons. In fact, as far as I know there have been different proposed distances, using different input data (word lists or others). From what I gather of your question, it seems like your interest in such a distance would be more practical than related to studying the shared history of the languages compared in depth, is that it? If so, you might look for a distance that more clearly reflects possible difficulties in communication (mutual intelligibility, maybe?), instead of something that accurately reflects shared ancestry itself. In other words, it might be a good idea to reflect on what you want this distance to tell you about the languages compared.

In any case, I've come across some papers dealing specifically with distances between languages and their appropriateness for describing language relatedness, which I've been meaning to read carefully for some time. Here are two:

Distributions of cognates in Europe as based on Levenshtein distance*

JOB SCHEPENS, TON DIJKSTRA and FRANC GROOTJEN (a1) https://doi.org/10.1017/S1366728910000623

and

Positing Language Relationships Using ALINE

Paul Huff and Deryle Lonsdale

Language Dynamics and Change, Volume 1, Issue 1, pages 128 – 162 Publication Year : 2011

DOI: 10.1163/221058211X577964

Hope this helps!