We Have Questions: How Did Humans Learn How to Speak

Thomas R. Sawallis, Louis-Jean Boë

History, Americas

Baboons make sounds, but how does it relate to human speech?

Sound doesn’t fossilize. Language doesn’t either.

Even when writing systems have developed, they’ve represented full-fledged and functional languages. Rather than preserving the first baby steps toward language, they’re fully formed, made up of words, sentences and grammar carried from one person to another by speech sounds, like any of the perhaps 6,000 languages spoken today.

So if you believe, as we linguists do, that language is the foundational distinction between humans and other intelligent animals, how can we study its emergence in our ancestors?

Happily, researchers do know a lot about language – words, sentences and grammar – and speech – the vocal sounds that carry language to the next person’s ear – in living people. So we should be able to compare language with less complex animal communication.

And that’s what we and our colleagues have spent decades investigating: How do apes and monkeys use their mouth and throat to produce the vowel sounds in speech? Spoken language in humans is an intricately woven string of syllables with consonants appended to the syllables’ core vowels, so mastering vowels was a key to speech emergence. We believe that our multidisciplinary findings push back the date for that crucial step in language evolution by as much as 27 million years.

The sounds of speech

Say “but.” Now say “bet,” “bat,” “bought,” “boot.”

The words all begin and end the same. It’s the differences among the vowel sounds that keep them distinct in speech.

Now drop the consonants and say the vowels. You can hear the different vowels have characteristic sound qualities. You can also feel that they require different characteristic positions of your jaw, tongue and lips.

So the configuration of the vocal tract – the resonating tube of the throat and mouth, from the vocal folds to the lips – determines the sound. That in turn means that the sound carries information about the vocal tract configuration that made it. This relationship is the core understanding of speech science.