It seems to me that every day turns up a new and exciting fact about the world’s languages. I recently read Laura Kalin’s account of Turoyo, a Semitic language spoken in Syria, which she describes as having a piece of inflection which is pronounced “l”, unless it comes between two consonants, in which case it assimilates to the preceding consonant, except that just in case it comes before a consonant and after something plural, it is pronounced “n”. (The paper was published in 2020 in volume 30 of the journal Morphology). For various reasons this is unexpected, including the fact that it is a suffix which seems to look “outward” to a following suffix to inspect its phonology before making up its mind about how to be pronounced. Kalin’s analysis takes this unexpected fact seriously and proposes that in this language, the phonology of the verb is determined from the outside in, so that the verb root is actually inserted after the suffixes, even though it is pronounced before them.

This analysis might receive some competition as alternative analyses are devised, but the descriptive facts about the pronunciation of “l” and “n” and the assimilated alternative are not in question, as far as I know, and I think this example provides important evidence for understanding how morphology works in human languages.

Test cases like this one require a number of different factors to come together. Finding similar examples to compare with this one is important in evaluating competing hypotheses about how they work.

Ethnologue states that 7,168 languages are in use today. The site also notes that 40% of languages are endangered. If you delve into the numbers, there are some causes to be concerned about linguistic diversity. 3272 of the languages listed in Ethnologue account for 99.9% of the population, and the other 3896 languages are divided unevenly among the remaining 8 million people. Many of them are not being learned by children at all; linguists call them “moribund”. 315 of the languages listed by Ethnologue are identified as having 0 speakers, so when they say that these languages are “in use” it is because they still have cultural significance for some community. The numbers in Ethnologue can be considered optimistic, and many small languages probably have fewer speakers than has been reported. Covid took a heavy toll among the elderly, and this has almost certainly led to the demise of several unique languages.

There is also another unsettling fact: The languages which are spoken by many people belong to fewer distinct language families than the languages which are spoken by few people. For example, there are 455 Indo-European languages spoken by 3.3 billion people, and 458 Sino-Tibetan languages spoken by 1.4 billion people and if we add the Niger-Congo, Afro-Asiatic, and Austronesian language families, then 6.2 billion people have a language from one of those five families as their first language. That means 85% of the global population are native speakers of a language related to English, Chinese, Arabic, Indonesian, or Yoruba (along with Igbo and Fula and all the Bantu languages).

There are hundreds of language families and “isolates” (languages which have not been found to be related to any other). A new fact or perspective is more likely to be found in an unrelated language than in one which is related to those which are already familiar. Our chances of accessing these new perspectives diminish as entire language families and isolates become moribund and die out. It is true that new languages emerge, but it usually takes great time depth for substantial differences to develop between two related languages. Turoyo has been diverging from Arabic and other Semitic languages for thousands of years. In this age of electronic communication, literacy, and concentrated urban populations, it is not clear that the same kind of linguistic divergence is likely to emerge as it did in the past.

There are a lot of reasons to be concerned about linguistic diversity, and to support efforts at documentation and revitalization. I have only mentioned some scientific reasons, but there are many others as well.