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What the Songbird Said
BBC Radio 4 and the World Service
Original broadcast: 12 May 2015 1102 GMT
Presenter/host: Angela Saini
Producer: Rami Tzabar
Transcript
Audio: birdsong, music, child singing mix FADES UP and runs under speech
Speaker montage:
It’s one of the most fascinating we do as humans and a mystery people have been trying to study for
years and years and years and still it alludes us …
SEGUE
We know that language appeared in evolution just out of the blue perhaps a 100,000 years ago but
it’s a huge mystery
SEGUE
If you look somewhere in the animal kingdom for some kind of parallel for language obviously you
should be looking at our closest relatives, chimpanzees for instance – but our closest relatives don’t
behave like that us at all in that respect but song birds for some reason do
SEGUE
I guess the most fascinating thing about it is the way kids are able to acquire this incredibly
sophisticated toolkit without needing to be taught it in any formal way
Audio: birdsong, music, child singing mix FADES down
Saini
For me as a parent, just how an infant goes from babbling to vocalising words and then stringing
those words into sentences, is remarkable. There are lots of theories about how we acquire
language but even more mysterious is the question of how it evolved in the first place. Fundamental
to answering this is the matter of whether language is unique to humans or whether elements of it
can be found in other species.
I’m Angela Saini and in this programme I’m meeting scientists who are exploring what animal biology
can tell us about human language. In particular, if the key to its complexity may be tweeting in the
trees above us right now.
Nightingale Song FX FADES UP
Saini
In 1871, Charles Darwin was amongst the first biologists to note the similarities between birdsong
and human language, in The Descent of Man:
Reader
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The sounds uttered by birds offer in several aspects the nearest analogy to language, for all the
members of the same species utter the same instinctive cries expressive of their emotions
Saini
Darwin’s thoughts reflect just how much we humans relate to birdsong. Poetry and literature are a
testament to our love of it. But is there something more to this? Does our connection go beyond
appreciation of its beauty – is there a deeper biological link between birds and humans, as Darwin
implied?
Actuality: Johan Bolhuis Zebra Finch song demonstration
Bolhuis
So this is the song of an adult zebra finch father
Finch song FX
Bolhuis
And now we hear the song of one of his sons, he’s got two sons here and they’ve been exposed to
the song of the father and this what one of the son’s has come up with when he is an adult himself
Finch song FX
Saini
So it’s pretty similar to what the father is singing
Bolhuis
Yes, he has copied it pretty well but this another son of the same father so he still has a long
way to go
Saini
Not as sophisticated as his brother
Bolhuis
No but it could be with more practice that he reaches the same level
Saini
Johan Bolhuis is a professor of cognitive neurobiology at the University of Utrecht in the Netherlands,
and he works with Zebra Finches, small Australian songbirds with bright orange beaks – their songs
are simpler and they have a far smaller repertoire compared to the nightingale, but they are easier
to breed and keep, making them perfect for research. He’s trying to unite biology and linguistics –
two fields that have traditionally had very different approaches to the question of how language
might have arisen. Biologists are looking for the details, while linguists paint big theoretical pictures.
I asked Johan Bolhuis what we now know humans and songbirds have in common…
Bolhuis
The way that children learn to speak is very similar to the way that song birds learn to sing. They
have to learn their songs from an adult individual. So that for instance there is a sensitive period, so
early in life a zebra finch learns much more easily than later in life and at some stage it can’t learn
anymore at all. And something similar happens in humans that a young child can learn a language
very quickly and can learn several languages at the same time, like my daughter did once and then
also if you look at the way that speech develops and that birdsong develops there are instinct
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parallels there too that there are different phases, so there is what we call in human infants we call
babbling, so they make funny little sounds and they haven’t got a clue what they’re saying but they
make those sounds and then very gradually they start to pronounce real words and maybe even
sentences at some stage. And more or less the same thing happens in songbirds, they also start – so
they listen to their parent, usually their father, usually it’s the males that sing in most species, and
then first they make little squeaky sounds, just like human infants, and then very gradually they start
to make real birdsong sounds. And at some stage – so first you’ve got sub-song, it’s like a babbling
stage and then later they become adult and they have adult song. And in some species that’s the
song that they live with for the rest of their lives.
So there are different as – there are different levels if you like. So at behavioural level there are
similarities with speech, there are also parallels at the neuro-level, the level of the brain, that, for
instance, that we have found ourselves that there are different brain structures involved in songbird
learning and they’re quite comparable to the brain structures that are involved in human infant
speech acquisition. And also what we found recently is that the two halves of the brain – we have a
left part and a right part of the brain and it’s mainly the left part of the brain that’s involved in
speech and language in humans. And we found exactly the same with the songbirds, that they also –
the young songbirds they process song, song that they hear from their father for instance,
particularly with the left part of the brain. This process of imitating and altering new sounds is called
vocal learning – it’s quite rare in the animal kingdom.
Zebra Finches FADE UP
Saini
An hour’s train ride from Utrecht is another bird lab filled with Zebra Finches – this time run by
Professor Carel ten Carte at the University of Leiden. He’s scoured the animal kingdom in search of
vocal learners.
Ten Cate
So there are about 27 or 28 different groups of birds – all ten thousand bird species fit into one of
those groups and of all those groups there are only three which vocal learning is present – the
parrots – we all know by imitation – the song birds – like zebra finches and then it’s the humming
birds and it’s probably the case that the ancestor of all those groups evolved vocal learning, because
virtually all song birds we know of demonstrate vocal learning – same with parrots – that means it
has evolved three times independently – and In mammals it’s also rare – humans amongst the apes
and all the monkeys as far as we know in the, present in bats, it’s present in dolphins, in whales and
in sea lions – and there are a few reports of elephants who are able to vocal imitate.
Saini
So quite a remarkable thing then…
Ten Cate
Definitely. It’s something that has appeared in the course of evolution a handful of times.
Saini
What sets human language apart though, from all these other species, according to linguists, is
grammar. The father of modern linguistics, the American intellectual Noam Chomsky, summarised
this idea in his theory of universal grammar. Essentially, grammar, or syntax, is innate – something
embedded in our brains, and so fundamental that even young children automatically grasp the rules.
They can understand the meaning of sentences even if they contain words they haven’t heard
before. This is why – to use one of Chomsky’s own examples – a sentence like colourless green
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ideas sleep furiously – makes grammatical sense, even if it doesn’t make logical sense. While the
sentence, furiously sleep ideas green colourless – makes no sense at all, grammatically or otherwise.
It’s the hierarchy of the words that’s key. But in the bird lab at Leiden University, they’re
investigating whether birds, too, use similar rules.
Ten Cate
Essentially We are interested in how the rules systems which underlie language how they might
have evolved and we want to know is there something – in other animals which might have might
provide a suggestion or hypothesis about how our complex rules might have arisen over the course
of evolution.
Saini
And what have Zebra Finches told you so far?
Ten Cate
So when you look at songs of Zebra Finch songs, they themselves are quite simply structured – and
not very elaborate, but that they are not singing very elaborate songs doesn’t mean that they are
not able to understand sequences of songs and detect the rules underlying sequences of elements
from instance. So what we are using is something called artificial grammar learning which has been
developed for research in humans and human infants in which you are only looking at the structure
of sounds.
Zebra Finch sounds fade Up
Spierings
…so this is one of the Skinner boxes in which we train the birds. As you can see there is a little zebra
finch hopping and it has two pecking keys, the red dots in the middle there? And the first key that’s
illuminated now, he has to peck it then he hears a sound…
Saini
Dr Michelle Spierings, one of Carel ten Cate’s PhD students at Leiden, showing me the artificial
grammar experiment, designed to see if zebra finches can perceive differences in the structure of
sounds – something she describes as being like grammar.
Spierings
We call it grammar-like, because it is related to human grammar but of course it is a very simplified
version. So what we do for instance is we have structures that are XYX, so the first one and the last
one is always the same
Zebra Finch sounds
..if you did this is in human language it would be lee-baa-lee for instance, versus structures that are
XXY – so the first two ones are the same
Zebra Finch sounds
..so that would be lee-lee-baa and those are very very simple rules, based on the rules that infants
can learn when they’re very young so 7 months old infants are known to be able to perceive these
rules, these XYX or XXY rules with the repetition or no repetition and if you present them with a new
rule they’ll be more interested in that rule – and they look longer and want to hear it longer which is
an indication that already at that age they can discriminate between these two grammar rules..
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Zebra Finch sounds fade down
Saini
As well as her vast collection of zebra finches, Michelle is also running the same grammar
experiment with another species - budgerigars, members of the notoriously talkative parrot family.
The question she wants to answer is this: Once the birds learn to differentiate between the two
sound structures, can they abstract this rule to new sounds that they’ve never heard before? This is
something a human baby can do at seven months.
Spierings
So what we found so far is that the zebra finches they’re not learning this abstract rule and the
interesting thing is that the budgerigars were able to abstract this rule this pattern behind the
sounds, because if we gave them new sounds, they were able to correctly distinguish it and to group
it accordingly to the structure of the sound. So it seems between these two species – although
they’re are both vocal learning birds there is a difference in what they’re able to learn and that
might have something to do with their cognitive abilities but it is at least something that seems to
have evolved in budgerigars but not in the zebra finches.
Saini
There is an idea in linguistics of universal grammar, is this what you’re talking about – a kind of
grammar for birds?
Spierings
I won’t say that the birds perceive it as a kind of grammar but what we can say is that they can
perceive the abstract rule that is behind this and of course we call it ‘grammar-like’ because we want
to relate it to something humans are doing but that doesn’t imply that the birds are perceiving it as
something grammatical
Saini
Michelle Spierings. This research is one piece in the biological puzzle that is language. Another piece
is genetics. Language leaves no fossils, of course. The next best thing may be to find clues to our
evolutionary history by studying our genes and see how they compare to other species.
Simon Fisher is Director of the Max Planck Institute for Psycholinguistics in Nijmegen, not far from
Carel ten Cate’s bird lab. Fisher is famous for having helped discover the FOXP2 gene, which some
people have dubbed the ‘language gene’. The interesting thing is that it’s also found in songbirds.
Fisher
I always resist this kind of idea of calling something a speech gene or a language gene because of
course genes do lots of different things and FOXp2, for example, does things in different parts of the
body – it’s important for lung development, gut development and things like that. So I’ve resisted
calling it a ‘language gene’. But what I would say is it’s a kind of a window into the way that
language works because we know that when the gene goes wrong, it seems to have problems for
the way that the brain processes speech and language. And a lot of insight into how FOXp2 works
has actually come from songbirds, from studying the way that the FOXp2 gene in songbirds impacts
on an ability of a bird to learn its song.
In fact we know that the gene is present in lots and lots of different species, so it’s not just having a
FOXp2 gene that automatically gives you the ability to do this. What we think is that FOXp2’s been
around for a really, really long time in evolution and one of the things it does is something in the
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brain that relates to sequencing of movements, we think. So it seems to be important for brain
circuits that help people to learn to make sequences of movements and we seem to think this
applies in other species, for example, in mice we’ve shown that this is important for motor
sequencing in mice. So the idea is that FOXp2 sort of in the right place to be able to help these kinds
of vocal learning processes to emerge and in some species it happens to have ended up being
recruited for that and in other species it hasn’t. And then the question is, what are the subtle
differences in the versions of the gene that it might have?
So sets of genes come out from that kind of study. And one of the things we’re trying to do is look to
see whether the genes that we find in one set of analysis line up with those from another
Saini
Right, so on your side what you’re doing is identifying so-called language genes, I hesitate to say
language genes I know, but genes connected to language and by seeing how they act in other
species you can draw some conclusions about the evolution of language?
Fisher
Absolutely, so what we do is we say right in modern human populations we look for variations in
genes that affect current language performance, mainly through studying people with disorders but
also we’re starting to look at how people in the general population who don’t have disorders – how
some people are better language learners than others. So we’re trying to track down the genes by
studying that. Now those genes then are prime candidates to trace their evolutionary histories and
ask what they do in other species, how have they changed in recent evolution and try and
understand their function and whether they’ve somehow contributed to our unique linguistic
talents.
Saini
Simon Fisher expects that over the next few years we’ll find more genes involved in speech and
language. He’s already working with Carel ten Cate on Fox P1, another interesting candidate – which
is, also, found in both zebra finches and humans. But Johan Bolhuis is not convinced that genes can
provide an answer to how language evolved.
Bolhuis
Language is about cognition, it’s about the way – it’s about the mind, the way we think, so it’s not
just about speech, for instance. And so therefore for instance the involvement in genes in language
there’s not all that much you can say about it, I mean the involvement of genes in speech, okay,
that’s an interesting – that’s an interesting line of research. But it doesn’t say much about language
as a cognitive structure. And maybe doesn’t say anything at all about language. Those discussions
are quite fierce …
Saini
…Simon Fisher would disagree with you.
Bolhuis
Yeah but – but yeah I with Chomsky on this one, that language is more than just speech.
Saini
This highlights one of the major characteristics of language research – huge disagreement. On the
one hand you have biologists, working from the bottom up. Working from the top down on grand
theories, are linguists. There are some linguists, for instance, who still refuse to believe that
language is connected to the animal world at all. They say it’s a phenomenon that emerged
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‘suddenly’ in the human brain up to 100,000 years ago. But biologists maintain that the roots of this
remarkable skill must have some remnants in our deeper evolutionary past. And if these remnants
exist, we should be able to see them in other animals.
Research on songbirds may bring these two sides together. In 2013 a Japanese linguist at the
Massachusetts Institute of Technology - a colleague of Chomsky’s in fact - proposed a novel and
controversial theory which tries to unite not just birds and humans but also our closest primate
relatives such as chimps – which don’t share our ability to vocal learn. He calls it ‘the integration
hypothesis’.
Miyagawa
The hypothesis that I put forth is that human language actually uses two pre-existing systems in
nature. One, a system that underlies communication system in primates, such as apes. And the
other is the system that we see in birdsong. Two fundamental different systems that in human
beings or homosapiens somehow uniquely came together and formed language.
Saini
Professor Shigeru Miyagawa. His hypothesis rests on an idea that language can be split into two
layers - a lexical layer, comprising words, which carry meaning – the way some primates use sounds
to refer to objects in the real world. The other is an expressive layer, which is a structure without
words , a bit, he explains, like birdsong.
Miyagawa
I was exploring an idea that’s well known in linguistics that human language is made up of two layers
of meaning. One layer made up of words and the other layer made up of the patterns that form a
sentence into which you plug in the words.
Vervet alarm calls
Miyagawa
A very well-known system is the vervet monkeys of Kenya where they have alarm calls for eagle,
leopard and snake. And so when a snake comes into the vicinity of the habitat one vervet monkey
will shout out alarm call for snake. And the entire community, you can see on a video, the entire
community climbs up the tree. And so these are individual items, lexical items…
Saini
Like words…
Miyagawa
Like words. They have real reference in the real world, like leopard and eagle and snake.
The expression layer is the layer that gives you patterns by which you convey intention, And with
birdsong that’s exactly what you have.
Nightingale song
Miyagawa
A nightingale can sing up to 200 different songs. But the purpose for these songs is pretty limited,
usually to mate and also to assert territory. Birds make all these patterns that they sing but each
song doesn’t have a particular meaning. And what human language has, which other systems don’t
have, are structures that we use to build grammar and sentences. And what the integration
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hypothesis says is that there’s a particular way in which we acquired in evolution the way to
construct these structures out of the two systems, the lexical system and the expression system.
Saini
So there are no animals that have both these layers, is that what you’re saying?
Miyagawa
There are no animals that have integrated these two layers. One thing that we’re looking at right
now is whether animals may in fact have both E system – expression system and lexical system but
as far as we know there are no animals, other than human beings, that have integrated the two
systems.
Saini
Miyagawa’s intriguing idea has certainly shaken up linguistics, but how did this system come about?
How is it that we and birds came to share this expression layer, as he calls it? Johan Bolhuis.
Bolhuis
Technically that’s called convergence in evolution – that for some reason different groups of animals
that are completely unrelated or very remotely related come up with some similar solution to similar
problems. And it works that way. So it’s similar to, for instance, that bats have wings and birds have
wings but of course they’re completely different kinds of wings – bats don’t have feathers for
instance – but they both can fly with it. Apparently they’re two completely unrelated groups of
animals have come up with something quite similar to solve a certain problem. And that has wrong
footed people in the past that the idea was always that if you look somewhere in the animal
kingdom for some kind of parallel for human speech or may be even language, obviously you should
be looking at our closest relatives, at chimpanzees for instance. But our closest relatives don’t
behave like us at all in that respect but songbirds, for some reason, do and that’s how evolution can
work.
Saini
What may help answer this tricky question would be if we could somehow find another primate that
showed evidence of both an expressive and lexical layer, like we have. A kind of missing link in the
integration hypothesis. Shigeru Miyagawa believes he may have found just the creature.
INSERT Gibbon Song FADE UP
Miyagawa
There is a primate – gibbons – that actually sing and their song is quite – quite – quite spectacular
and they sing for an extended period of time. And their song is in many ways similar to birdsongs,
you can sort of map it out in grammar.
INSERT Gibbon Duet song FADE up
Clarke
Adult male and female that are paired together will sing what we call a duet every morning. It can
travel about a km to advertise the pair’s relationship, ie their pair bond and also to enable spacing
between groups. So in the morning about 1-2 hours after sunrise, all groups with start singing their
duets and the entire forests is awash with this calling
INSERT Gibbon Duet song FADE down
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Saini
Dr Esther Clarke from Durham University has analysed duet songs and found that gibbons can
recombine sounds, changing their songs in order to refer to objects in the real world – in this case
predators like snakes and leopards.
Clarke
What I found is that they’re using exactly the same call units in both types of songs but they’re
rearranging them. So in the duet context you find, typically 6 or 7 different kinds of note and the
same kinds of note in the predatory context but in the duet context interestingly in the the initial
segments of the song they tend to introduce more of what we call leaning waa notes (vocalises: waa,
waa!) and less of what we call ‘hoo’ notes (vocalises: hoo! Hoo!), whereas in the predatory song it
was the complete opposite way round.
Actually these songs are actually quite complicated and not just this sort of advertising territorial
function, I think here is some very simple level of syntax going on, they’re rearranging the different
notes to denote different contexts.
My most recent paper looks at the quiet calls of gibbons – these are known as ‘hoos’ and what I
found is they’re giving different ‘hoos’ in different contexts, so I’ve been able to split what we
thought of traditionally a single call unit into at least 6 different sub units that are consistent across
all individuals in all these different contexts so basically what tells us is that the gibbon vocal
repertoire is potentially much larger than what we originally thought. And we’re still really
scratching the surface here and not sure what we’re going to find and if we give looking and
analysing the gibbon song we’re going to find that there is a lot more flexibility in it than we
originally thought.
Saini
So Miyagawa’s theory s that human language takes a lexical layer from primates and an expressive
layer from birds, what do you think about that?
Clarke
What’s exciting about this work is that there’s potential that gibbons could merge these together. So
they have these songs used in territory defence and in mate attraction like birds – that fulfils the
expressive layer, but they also have the ability to vocally distinguish between different predators, so
that sort of feds into the lexical layer so I suppose here the potential is that gibbon song could
possibly be an interesting avenue to look at how those two layers might come together in a nonhuman primate.
Saini
The work of scientists like Esther Clarke is giving us a better insight into what primates are truly
capable of when it comes to language. Coupled with birdsong research, this gives theorists like
Shigeru Miyagawa something rare in linguistics – a chance to put real meat on the bones of the big
ideas. Together, biology and linguistics may finally answer the question of how human language
evolved. The clues are all there, they say – singing as we speak.
Birdsong, Music and child babbling mix
Ten Cate
There is a lot going at the moment – the field is really very vibrant and people starting to develop a
common language, at least getting more and more grip about where the big questions are. Whether
we will ever solve that question I don’t know – it might be an unanswerable question.
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Fisher
We can’t just make up stories any more, we have to say ok here is my idea about how language
works or where it came from, here is how you can test that and here is how you can see if it is
different from someone else’s idea and I think that is what is exciting at the moment, people really
are coming out with testable hypothesis and part of that is being able to think about what is going
on in other species.
FX: MUSIC birdsong/baby duet FADES slowly
END