The layered language of great apes

Could some of our closest relatives share our sophisticated sentence structures...
14 May 2024

Interview with 

Adriano Lameira, University of Warwick


Adult orangutan


But first, we’re going to talk about Russian Dolls. It’s a term that linguists use to describe one phrase fitting inside another - which is a characteristic feature of how humans speak. For instance, I might say, “when I left home this morning, because it was sunny, I didn’t take my umbrella.” We thought that was uniquely human. But now comprehensive analysis of vocalisations recorded from orangutans has revealed to Warwick University’s Adriano Lameira a similar pattern of “speaking”. So, is this pointing towards the evolutionary origins of how we humans learned to talk?

Adriano - I study great apes both in the wild and in captivity, to really try to understand and decipher their vocal communication. Because a lot of times we know that our species is unique in terms of our language capacity. And oftentimes we quickly assume that we are categorically different from our closest living ancestors, the great apes, when in fact we draw these conclusions without actually putting in the necessary effort to prove that those capacities are indeed absent in our closest living relatives. And so I kind of use and study great ape communication, cognition, cultures as a time machine to go back to our own ancestors and try to understand what they were capable of and why did that steer our lineage towards what was to become one day fully fledged language.

Chris - Because people often say that some dramatic jump or mutation or shift happened that endowed humans with a range of things, including language. Whereas if what you are saying is true, then it's a more gentle slide in evolutionary terms where various building blocks are assembled and then slowly come together in us to give us those abilities. So they should therefore be vestiges of those building blocks out there in the natural world. We just need to find them?

Adriano - Correct. Exactly. So actually the principles of evolution by natural selection tells us that we should expect those gradations, we should expect a continuum within phylogenetic families.

Chris - How did you put this to the test?

Adriano - So actually the behaviour came to us. We were following wild orangutans daily and recording every vocal behavior that they did because we want to catalog their repertoire before they go extinct. And when we started to try to really quantify the characteristics of these loud calls produced by males, we started to see hints of different layers of signals.

Chris - When you say layers, tell us a bit more about what you mean by that and why that's special.

Adriano - Right. So as layers, I mean different levels of organisation. So this characteristic of putting a signal or a pattern within itself or within a similar signal or pattern. An example would be Russian dolls where you have one doll that fits within itself. This is important because this is how we tend to organise our own stream of words and sentences. I can be saying a phrase and then insert another phrase in there to further explain my point, and then I step out again of that little clause and I continue my original sentence. So this is something that languages do all the time. It's claimed to be universal and therefore claimed to be one of those things that really makes human language distinct from every other animal vocal system is that only we can insert a sequence of sounds within another sequence of sounds. And so when we started to see hints of layers in wild orangutan loud calls, we thought maybe this is the type of evidence that has been missing.

Chris - You've sent me some examples of what you recorded. Can you talk us through what we're going to hear here, and signpost us towards each of the examples? So which one would you like to start with and just tell us what we're gonna hear before we play it.

Adriano - So I brought two recordings along. The first one are the pulsar, which are kind of the climax of the wild orangutan loud call. These are the kind of extended notes to be heard and broadcasted across large distances of the forest. So these we can think of as the larger Russian doll. Exactly. So these, these are the extended notes that carry over the course so that other orangutans, both females and males hear the calling male.

Chris - And those punctuated loud noises, those are the big outer Russian doll. So those are the sounds that you are saying if I was speaking to you and I wanted to include a phrase inside something I'm already saying, those would be the outer capsule as it were. And now we're going to think about what's going in the middle?

Adriano - Correct. We are gonna hear grumbles, which we can think of as the smaller layer of our sound Russian doll. So we can still see here the pace of the larger notes. Right? We can hear <sounds imitation> so we still have the tempo of the larger pulses, which kind of the carrier bray, so to speak, the larger doll. And now we have smaller nodes, staccato notes with their own little tempo inside the main beat <sound imitation> regular, notes inside regular notes, which kind of effectively is an example of a pattern nested within itself.

Chris - You are arguing that because they can do this, that is the foundation for what we do when we are actually nesting phrases and doing recursive speech patterns.

Adriano - Exactly. So one of our most important tasks here was to try to disentangle are these not just the result of a bodily resonance, for example. And so what we found is when characterising the two tempos and seeing their relationship, their ratio, the quicker, smaller tempo was not related to the larger one. And so what this led us to conclude and be able to exclude the possibility that the smaller tempo is indeed not an artifact of the larger one or vice versa,

Chris - Given that orangs are more distantly related to us than say chimps and bonobos are, if they've got this and this is part of the origin of us being endowed with a similar ability, does this mean it should be in other great apes? And is it therefore a question of going, looking for this now in bonobo and chimpanzee vocalisations, for example, which would give confidence to what you are saying is, is right?

Adriano - Absolutely. That's an excellent question. And yes, that would be the assumption. If orangutans being the earliest diverging lineage of great apes, one would assume that closer related lineages to us, such as chimps and vulnerables and gorillas, they would also have. However, I think right now the understanding is that all the great apes really need to be treated as a family because different lineages have gone to do different adaptations. So for example, we know that our last common ancestor with great apes was not as terrestrial as chimpanzees and bonobos and gorillas. And so in terms of lifestyle, actually orangutans, although genetically relatively further, they still live a lifestyle and an environment that is actually closer to what our ancestor lived with. And so I, I think in this sense, we should definitely go and search in the African apes. The clues may be there and they may have been hidden in plain sight just like they have in the case for the orangutan long calls.


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