Welcome to another week of Dear Duolingo, an advice column just for learners. Catch up on past installments here.

Hey there, learners! This week's question is for the language nerds among us 🤓 Has it ever crossed your mind, maybe while watching a Shakespearean play or reading about the history of languages?

Our question this week:

Illustration of a letter to Dear Duolingo that reads: Dear Duolingo, How do linguists know how languages used to sound? Thank you, Whispers of the Past

For some languages, linguists know a great deal about how they used to be pronounced (and what their old grammar and vocabulary were like), even if the languages are no longer spoken, like Latin. There are some clever tools and strategies available to understand old pronunciations!

But it's also true that there is always some degree of uncertainty and that we know much more about some languages than others. As you'll see, having a written record of the language is really helpful, as is having information from related languages. After all, not all languages have writing systems, and many writing systems are still quite new!

Here's how linguists do this detective work! 🔍

First, it's helpful to think of languages like a family tree: One language can give rise to "daughter" languages that can all trace their origins back to that common language, and those daughter languages will share some things in common but will also have traits all their own. This happens because any one language is actually a group of dialects—and sometimes, those dialects can grow distinct enough from each other over time that they become their own languages.

Linguists decide if languages are related—if they are daughters, or granddaughters, or great-granddaughters of a common language—by comparing their vocabulary and grammar. And comparing their sounds and modern pronunciations can help them decide if two seemingly different words in daughter languages actually came from the same word in a common language long ago. It's like a multi-century (or multi-millennia) game of telephone! 

So to have a sense of how the parent language was pronounced, linguists will compare the sounds in the daughter languages and make some hypotheses.

Method 2: understanding common sound changes

In order to do those sound comparisons, linguists need to know about the relationships between sounds and the changes that are likely to happen to them. 

For example, the sounds "g" and "k" are made in the same part of the mouth with the same tongue movement, so it's not unusual for one to replace the other gradually, over time. On the other hand, "g" and "f" are pretty different: They're made in different parts of the mouth, with different movements, and only one requires vibration in the throat. (You can see each sound's traits in International Phonetic Alphabet charts.)

That means some daughter languages having a "g" sound where others have a "k" sound wouldn't be too surprising—but swapping "g" for "f" from parent to daughter would be unusual.

Besides the relationships between individual sounds, there are other kinds of common patterns linguists look for. Let's keep comparing "g" and "k," since the only difference between these sounds is voicing: We vibrate our vocal folds to make "g" but we don't for "k," so we can call "g" voiced and "k" voiceless. There are some patterns we find across the world's languages and dialects:

  • Devoicing at the ends of words. At the ends of words, phrases, and sentences, it's common for certain kinds of voiced sounds (like "g") to become voiceless (like "k"). In fact, this pattern is the rule in many languages—for example, in Catalan, German, and Russian, words that end in -g are actually pronounced with a "k"!
  • Voicing between vowels. If a voiceless sound occurs between vowels (which are typically voiced), it's common for it to become voiced. For example, the Spanish nouns that end in -dad (responsabilidad "responsibility," habilidad "ability") came from Latin words that had a "t" sound between the vowels—and Italian and French still have that original "t" (compare Italian responsabilità and French responsabilité).
  • Voicing when near other voiced sounds. If a voiceless sound occurs next to a voiced sound, it's common for it to become voiced, too. For example, many Spanish speakers pronounce desde (since) with a "z" sound—the "s" sound is voiceless, but "d" is voiced, so the voicing sort of spreads from one sound to the other!

And there's so many more patterns, and so many more sounds than just "g" and "k"! With this arsenal of linguistic facts, comparing languages to decide if they are daughters of a common language becomes a puzzle of fitting in common patterns, in the right order, to decide how likely it is that one language evolved into these two daughter languages. Once you have those changes worked out, you can see which sound was more likely to have been in the parent language!

Method 3: examining the written record

For understanding changes within a single language, there are other tools available to linguists.

For example, to understand how Middle English (the English spoken from ~1100 to ~1400) was pronounced, linguists combine insights from at least three sources:

  1. Knowledge of how English words are pronounced today, across many dialects
  2. The (mis)spellings used for a given word
  3. What other people wrote about pronunciations

For #1, that's basically the same as the sound comparison methods described above.

For #2, there's something you need to know about linguists: They love typos. Mistakes! Misspellings! Variations! They all tell us something about what the writer thought of the word. English linguists of the future will be delighted to read text messages and social media posts where there, they're, and their are interchanged 😍 They let us know that despite spelling differences, these words are pronounced the same. And these totally natural slip-ups didn't start with modern internet users: As long as there has been writing, there have been mistakes. And how lucky we are to have them! Until relatively recently, writing and education were only available to the privileged, and likewise having standardized spellings is pretty new. The journals, letters, and even graffiti of common people reveal how words sounded—irrespective of their "standard" spellings.

The other useful kind of writing for this task—source #3—comes from early linguists, philologists, and people like you: language students! Academics, amateurs, and those studying new languages (or even just remarking on how other languages sound) often made notes about pronunciation—for example, they might say that a sound in a particular language or region was pronounced quite unlike (or very similar to, or to rhyme with) another word. These reflections are a treasure trove for linguists!

You can hear the past…

…if you know how to listen!

For more answers to your language and pronunciation questions, get in touch with us by emailing dearduolingo@duolingo.com.