How Amazonian drum communication sounds (and acts) like human speech

In the forests of the Amazon, West Africa, and Asia, villagers often beat on large drums to send messages miles away. While you may think that the patterns are similar to Morse Code, they're actually simplified versions of the villagers' spoken languages, "without consonants or vowels but with enough connection to the original language that speakers can reliably interpret what they mean." In newly published research, University of Cologne linguist Frank Seifart and his colleagues reveal how it's done. From Science:

All but one of the 20 or so drummed speech systems come from tonal languages, including Yoruba in Nigeria, Banda-Linda in the Central African Republic, and Chin in Myanmar. Spoken Bora has two tones, which are recreated using two different drums made from hollowed logs, called manguar. The thinner male has a higher tone, and the thicker female has a lower one.

But tone alone isnt enough to distinguish all the words a drummer might want to say. So Seifart and his colleagues looked at what he calls a neglected quality in linguistics-rhythm...

The intervals between beats changed in length depending on the sounds that followed each vowel. If a sound segment consisted of just one vowel, the time after the beat was quite short. But if that vowel was followed by a consonant, the time after the beat went up an average of 80 milliseconds. Two vowels followed by a consonant added another 40 milliseconds. And a vowel followed by two consonants added a final 30 milliseconds.

These short durations are enough to distinguish the drummed messages for go fishing and bring firewood, which are identical in tone, but not in their ordering of consonants and vowels. That means, the researchers write, that rhythm plays a crucial expressive role in drummed languages.