What singing lemurs can tell us about the origin of music

This is a lemur. It’s singing.

These critically endangered creatures are found only in Madagascar’s rainforests and are known locally as indri indri.

They sing in choirs, duets, and solo.

Sure, these don’t sound like Billboard Top 10 hits.

But scientists, like this one –

[Chiara]: Hi, I’m Chiara

…have spent more than a decade collecting songs from 20 indri groups.

And for the first time, they discovered that these songs have rhythm. Specifically, rhythm that appears in human music.

As in, literally, the beginning of this classic song.

The indri is one of the very few primates to share this very human trait with, well, humans – making them a precious clue in the search for the evolutionary origins of music.

So, why do lemurs sing? And what can our distant cousins tell us about human musicality?

Part 1: What is “singing” in the animal world? How do we define singing?
First up: how do scientists define singing in the animal world?

The sounds indris make can be broken into two categories: call and song.

This is a call.

[Chiara]:
“Calls are usually less complex than songs and are most often composed of a single sound. They lack complex and melodical organization.”

Calls are used as alarm signals to warn against predators,

and as a way of “getting attention” from others before singing in a group.

And this is a song.

[Chiara]:
“Songs are longer, more complex, and are composed of different kinds of notes following an order.”

Simply put, indri songs display common musical components that exist in human music.

Here’s a human –

[Jean]: Hi, I’m Jean.

…demonstrating musical components that appear in indri songs like:

[Chiara]: Pitch, Melody, Tempo

And most crucially, Rhythm.

Also defined as the placement of sounds in time.

It is the one indispensable element of all music.

Chiara’s recent study discovered two examples of human-like rhythm in indri songs:

A 1:1 rhythm, where

[Chiara]: “Intervals have the same duration, like the sound of a metronome.”

Kinda like this song.

And a 1:2 rhythm, where the second interval is twice as long as the first.

Listen to this recording of an indri.

The combination of regular intervals between notes gives this song the same rhythm as Queen’s famous song.

Listening to a piece of music is a super complicated endeavor – your brain processes a complex array of sounds, extracts information from it, and predicts what happens next.

It’s pretty amazing that our cousins have the same ability.

Part 2: Why do they sing?
So why do indris sing?

[Chiara]:
“There are different types of songs that we have investigated – three types.”

1. Advertisement songs, given each morning when the family groups wake up.
2. Cohesion songs, a way for the animals to find each other and reunite in the forest.
3. Territorial songs, given when two family groups are in visual contact and start this kind of vocal battle.

But the jury’s still out on why lemurs developed singing behavior in the first place.

Scientists believe it’s because rhythmic songs are easily distinguishable in the cacophony of the rainforest. But it’s still a theory.

Part 3: So what?
The animal world is rich in song and rhythm.

But indris are special because they are our closest living relatives.

[Chiara]:
“This may have also played a role in the evolution of our language.”

This finding contributes to the ongoing discussion around the “musical protolanguage hypothesis”

—a Darwinian theory that language and music originated from a pre-linguistic stage that was more like music than speech.

It’s still unclear whether indri song was a precursor to human song,

or if our rhythmic abilities evolved independently.

But this work is the starting point to figuring out more.

There are fewer than 10,000 indris left in the wild, and they’re constantly threatened by habitat loss from deforestation and pollution.

Hopefully, our shared traits…

…can remind us that we are animals ourselves, living in a world that is crucial to preserve.

Much like the origin of language, the origin of music has been a topic of great speculation and debate for centuries.

Charles Darwin thought that “some early progenitor of man” started singing crudely, “as do some of the gibbon-apes at the present day,” “during the courtship of the sexes.” In other words, Darwin thought songs and musical expressions appeared and then proliferated because our ancestors noticed music could get them laid.

Others suggest that music is merely an adaptation from an ancestral trait, such as territorial calls and signals.

A new study adds weight to this line of thinking. Researchers at the University of Warwick, the University of Torino, and the Max Planck Institute for Psycholinguistics found that Madagascan lemurs—small black-and-white primates—make rhythmic “honks” during their alarm calls. It sounds a bit like a car horn.

But to understand the rest of the story, first we need a music lesson.

What are the elements of a song or music?

This is a beat – the steady pulse of a piece of music that remains constant throughout.

Rhythm is made up of changing patterns of long and short sounds, as well as silences. In human music, it’s laid on top of the beat.

This is a rhythm.

A rhythm, when made up of notes with pitch, becomes a melody.

Indri songs have been known to contain notes organized in phrases.

[first study]

But scientists have recently proven that their songs contain rhythm too – specifically “categorical rhythms.” This type of rhythm refers to intervals between sounds that have exactly the same duration (1:1 rhythm) or doubled duration (1:2 rhythm). Even when sung at different tempos, the categorical rhythm is what allows songs to be easily recognizable.

The lemurs’ songs matched two rhythmic categories: a 1:1 rhythm—a pace akin to a metronome; and a 1:2 rhythm—like the stomp-stomp-clap of Queen’s “We Will Rock You.” Additionally, when indris sing, they gradually decrease their tempo—described in musical terms as ritardando.