Many animals produce song, but for one species, the vocal repertoire stands out as remarkable. Their calls, specific to their social group, combine a basic set of sounds into endlessly varied combinations. These are enhanced by altering rhythm, pitch and stress, and are complimented by gestures, sometimes using the entire body.

These calls transmit sophisticated information. The meaning of each compound sound depends upon its position within their song-like phrases. Each phrase is complex, and meaning is added to when phrases are combined.

Making these vocal calls requires the coordination in sequence of some 40 muscles in the mouth and throat. But there is one snag; the vocal anatomy which allows these animals to articulate their calls also predisposes them to a high risk of choking.

And to observe one of these extraordinary creatures, look in a mirror. Meet Homo sapiens; sound-smith, toolmaker, storyteller.

---

The possession of speech is the grand distinctive character of man“

[Thomas Huxley, 1871]

We enjoy a unique legacy; language. This is paradoxical; the physical attributes that together make our speech possible are not exclusive to humans, although evolving our particular combination of them is indeed novel, as are its consequences. Our habit of communicating by speaking has re-structured our entire ecology.

Speech sets us apart, defines how we understand ourselves, and codes our behaviours and habits. Through language we cooperate, adapt to our circumstances, share and use knowledge, coordinate our behaviour with others, align our actions with our intentions, and reach outacross the boundaries of time and space.

“We are more alike, my friends, than we are unalike” (Maya Angelou)

Language then, appears to define who we are. This opens up many questions.

How can we define language?

Language is a human-made tool that fulfils specific needs. A biologist would regard speech as a behaviour which is integrated into how the body works, and which enabled our ancestors to survive better. We are proof that this is so. For speaking to have evolved implies that our current form of language behaviour arose and was refined gradually through natural selection.

Language, like our other complex behaviours, is learned. Children do not learn to speak without contact with other humans. Our language skills develop into adulthood and change continuously; we are always acquiring and using new words.

Other animals and birds that learn complex forms of song have a sensitive period for learning these calls (the ‘imprinting period) which reduces substantially as they mature.

Whether ‘imprinting’ also applies to humans is controversial. We cannot easily assess whether an adult student, meeting a new language starts from the same basis, is exposed to the same amount of data as a child acquiring their first language. Also their reasons for learning are different; children are building a sense of identity as they grow their speaking capacity. This difference affects how people learn at different stages of their lives.

The case of Kaspar Hauser gives us some insight. This boy first encountered language in his teens. When later enough vocabulary had been acquired, he was able to describe some of his earlier life, indicating that he was able to ‘think’ before he could speak. However he never fully mastered grammar. It is this additional level of word ordering that allow us to sort and structure our thoughts.

Most likely, the sophisticated songs of some birds, dolphins and certain other social mammals are driven by sexual selection. So too is the descent of the larynx in human males at puberty, which affects the pitch of their voice. This suggests that human vocal calls have been important for mate choice at some stage in our evolution. However our main vocal differences, revolving around vocal pitch and tone, mostly reflect the individual’s body size. We have no gender bias in our capacity for speech, suggesting that selection for language provided our ancestors with group-wide survival benefits.

Although we can assume that language-based survival advantages have driven the evolution of our sound-making apparatus and the mental processes that we use for speech, language also codes information that we inherit. Crucially, this is independent of our genetics. Selection for access to this cultural information acts at the level of our social group. It has crafted us into a diverse population of accomplished makers and sharers of sound, movement and meaning.

What does our language enable us to ‘do’?

i. We express the contents of our minds through physical movement

We speak by moving our bodies in a way that generates signals in one or more communication modes. Although we tend to conform to our group’s agreed use as to what words mean, we make this ‘dance’ of stylised gestures our own. The sound of our voice, like the way we walk, and even the way we sign our name, is individual, distinctive and recognisable.

ii. We order our thoughts (and actions) into sequences

Often we mentally list our tasks, and imagine carrying them out in a specific order before we act. In this way, we use language to define, structure and plan out our experience.

iii. We code our experience with meaning

We share an understanding of word meanings with other users, although we code that meaning individually. Thinking of a phrase, such as ‘moved to respond’, activates the mirror neuron network. This maps our physical and emotional understanding of the words onto relevant areas of our brain, in particular the sensori-motor cortex and limbic system. Our internal coding of words depends upon the emotions we tag to our memories, and relates us to a physical, ‘embodied’ experience of their meaning. iv. We shift our awareness between details and concepts

When we turn a verb into a noun (e.g. speaking becomes ‘speech’) we have generalised an action idea into a more abstracted form. This assigns a symbolic understanding to the new word. As we relate them, our experiences become coded as concepts and metaphors; in this way big ideas are put into words. We also code meaning through sayings and stories.

v. We define our reality in various ways.

Ever heard of ‘performatives’? These are a special class of verb whose utterance changes our circumstances.

– When a judge declares ‘I sentence you to life imprisonment’, this statement alters the course of the life of its recipient in the dock.

– Oaths, e.g. marriage vows, are performative statements. These declarations of intention commit us to a voluntary long lasting change in our behaviour.

– Coining or learning new words brings these new ideas into our consciousness. This opens up new possibilities and affects how we respond to our circumstances. Our values, the things that are important to us, inform the beliefs we hold around our sense of self, and affects the way we derive meaning from our experiences. We internally translate our beliefs and values as presuppositions, i.e. what we assume is true about our world. These define what we allow ourselves to think, inform how we behave, and determines how we respond to and evaluate our circumstances.

vi. We visit experiences outside of the present moment

When we re-live our memories, and access the memories of others, we ‘travel’ in time and space. As we re-visit our memories, our past thoughts reappear in the present moment, and in a different location. Telling others about something allows us to journey with them through the story.

Typically we mention only the important details; this filters the narrative for its meaningful events. Telling a story in a different way, or altering the sequence of events in a tale, can alter how we feel about and relate to these events. This ‘reinvention’ changes their meaning.

viii. We become more like each other as we connect through language To have a conversation, we accept a shared understanding of meaning of our words, how we order them into phrases, and the beliefs and values that are coded into the expressions we use. By ‘speaking the same language’, we connect with and accept a ‘cultural norm’.

For language to have had a selective advantage, the benefits of conforming to the behaviour of our cultural group must have outweighed the reproductive success of being a ‘maverick’. We are living proof that this symbol-based group communication system works. Choosing group cooperation through collective action enhanced the survival of our ancestors.

Does this define how we think?

Asking ‘how does language enable us to think?’ presupposes that thinking involves language. This constrains what we might think of as ‘thinking’. ‘Thinking’ can and does take place without speech. If we focus our attention to listen to or look at something, we are directing our actions and thoughts without using language. Presumably animals ‘think’ in this way.

Language, however, takes us into a different mental mode from animal thinking. We use words to articulate the contents of our own minds to ourselves. Words link meaning with sounds, gestures or images that need not bear any relation to what they symbolise. Accordingly, we are the only animal capable of coding meaning into symbols and communicating our understanding through how we combine them.

A very few species of animals, e.g. dolphins and elephants, can recognise themselves in a mirror, as demonstrated by the way in which they use this reflection to examine a mark placed out of sight on their body. This implies that they understand the difference between ‘self’ and ‘other’ (a ‘theory of mind’).

When we ‘think’ about something, it goes beyond what we see, hear and feel. Information is processed by the unconscious mind. This then presents our conscious mind with a constructed representation of what we perceive, tagged with an emotion which codes meaning into the content of the thought. The way we build this internal world is affected by both our personal perspective, and our shared cultural experience.

Words define what we think something is, and therefore also what it is not. This frames our awareness of it, creates boundaries around what we perceive, and directs the level of attention we give it. Questions frame our choices to a reduced number of alternatives (“Is it this, that, or even those?”). This limits the number of possible outcomes. However we define thinking, we are the only animal capable of thinking about thinking. This is a unique feature of human language, and idea underpins Descartes’ famous phrase;

I think, therefore I am

What do we think about language?

Studies of language have varied between two viewpoints which highlight a bigger question: how we think about our physical selves. The ‘classical’ view of self thinks of the body as functioning separately from the mind (a ‘mind-world’ perspective). Thinking of our language in this way leads us to suggest that our ability to speak develops ‘innately’, much like our limbs and kidneys, and presumably through a genetically controlled process. In the 1960’s Joseph Greenberg suggested that in all human languages. words like nouns and verbs play similar roles. Noam Chomsky then developed this idea into his ‘theory of language’, suggesting that all human languages have a similar basic structure, which he calls a ‘universal grammar’. His framework has provided the starting point for a systematic study of what human language is.

Chomsky’s ‘universal grammar’ presupposes that all human languages are much the same. In this model, differences in vocabulary and word order are seen as ‘parameters’ (characters), and that any language is built from a subset of these characters. He has famously suggested that:

“…if a Martian was looking at humans the way we look at, say frogs, the Martian might conclude that there’s fundamentally one language with minor deviations.”

The Chomskyan view suggests that variations between languages, like the ordering of nouns and verbs, represent a limited set of choices. In this scenario, it is proposed that a child learning its first language would select from these choices through a genetic or developmental mechanism, triggered by the language input they receive. This idea is reminiscent of bio-genetic switches which ‘shuffle’ between genes, e.g. those that encode how quickly a virus induces symptoms in its host. This would imply that our children ‘look for’ cues to indicate which word order setting they need to ‘activate’ at the genetic level.

Frequency distribution of word order in languages, after Tomlin (1986) p22.  S = ‘Subject’ (noun performing the action in the phrase), O = ‘Object’ (noun acted upon), V = ‘verb’ (the action which is performed).
Word order	Short clause equivalent in English	Proportion of world languages with this pattern	Examples
SOV	“She him hears.”	45%	Japanese, Latin, Turkish
SVO	“She hears him.”	42%	English, Mandarin, Russian
VSO	“Hears she him.”	9%	Hebrew, Zapotec, classical Arabic, Irish, Welsh
VOS	“Hears him she.”	3%	Malagasy, Baure
OVS	“Him hears she.”	1%	Apalaí?, Hixkaryana?
OSV	“Him she hears.”	<1%	Warao

What might these cues be? The three-word ‘short clause’ is perhaps our simplest form of syntax, and is present in every language. In this phrase an item (the subject noun, S) acts on another item (the object noun, O) and the nature of that action is indicated by the verb (V), e.g. ‘scissors cut paper’ is SVO. Across the world’s languages, these words are used in all of the possible orders. However some of these forms are rare.

This uneven ratio of word ordering is reminiscent of the different ratio of forms (alleles) known for some genes. For example, genes encoding subunits of haemoglobin are found in almost all vertebrates, some invertebrates, and even some plants. Haemoglobin is found in our red blood cells; it binds oxygen at the high concentrations in our lungs, and releases it elsewhere in the body. Various forms of globin genes exist.

Most of us carry two ‘normal’ copies of the beta-globin gene (HbB) on chromosome 11, one on each of our chromosomal pair i.e. HbB/HbB. The HbS allele causes sickle cell disease (a form of anaemia) when one gene copy is present (i.e. HbB/HbS). Two HbS copies are lethal; not surprisingly, this keeps the mutation at a low frequency in most populations. However in West Africa, where malaria is a major scourge, 25% of individuals are HbB/HbS. The sickle cell condition provides some resistance to the malaria parasite, hence selection in this local population has acted to maintain this gene at a higher frequency.

Does selection in this way also apply to language structure? There is no clear indication that it does; there seems to be no obvious situation that favours some short clause options over others. After all, they all perform their function equally well. If word order had a genetic basis but no selective advantage, we would expect a more even distribution of forms in our languages worldwide. In practice, the form of a language’s short clause depends upon the cultural family from which that language arises.

Far from having a genetic basis, this view anchors grammatical structure to its history and circumstances. Nicholas Evans and Stephen Levinson have shown that the main characteristic of human communication worldwide is not its commonality, but its variation. Language forms vary so radically that in reality they find ‘vanishingly few universals’. Instead, human speech is characterised by its diversity in all aspects of its production including sound, meaning and syntax.

Whilst it seems that the grammar and syntax of language have no genetic basis, still we must have evolved our current capacity language. Our language function requires a physical means to produce the diversity of human speech sounds, and a cognition that allows us to think about what to say and understand what others are saying. These physical and mental capacities are not separate. Darwinian selection acts on whole bodies, meaning that language evolution, like the neural coding of our speech, is an ‘embodied’ process.

Philip Lieberman’s work has focussed on how the physical apparatus required to produce our speech may have arisen. He suggests that increases in the potential diversity of our ancestors’ speech signals were made possible by changes in their vocal tract, which were required to adapt their breathing and balance to fit an increasingly upright posture and bipedal locomotion.

Maintaining our posture would have required better fine motor control of the muscles used for balancing, breathing and eating, and also freed the hands, enabling better manipulation of tools. Chimpanzees do not have our levels of fine motor control. Producing sequences of actions involved with using manual tools have similar cognitive requirements to producing ordered sequences of speech sounds. In essence, evolving to ‘stand on our own two feet’ may have taught us to coordinate not only our walking but also our hand and finger movements, our voices, and possibly our thinking.

When we communicate, we physically relate to each other’s internal world through the actions of our mirror neurons. The chemical messages that these and other nerve cells use to ‘talk’ to each other are also recognised and produced by the cells of our immune system. In addition, our gut produce these same neurological chemicals as are found in the brain. This shows us that at the level of these information-carrying molecules, our mind and our physical body are in practice a single entity (a ‘body-mind’). This body-mind interacts with its environment, and changes biochemically according to the food we eat, the air we breathe, what we choose to think, and the company we keep.

Daniel Everett ’s lifetime study of the Pirahã people from the upper Amazon provides clues as to how our culture and language fit us to our environment. The Pirahã value self-reliance and eye-witness experience. They avoid assimilating non-Pirahã words into their language because they consider their traditional ways to be superior. They never combine their short, one-verb sentences into longer phrases (meaning they lack ‘classic’ Chomskyan recursion ), although they do combine ideas recursively by using sentences together. They use only a minimal form of past tense, and lack a mythology and a concept of numbers. Yet their cultural knowledge and attitude equips them to survive easily for many days in the jungle, as Everett puts it, ‘…equipped with only their wits and a machete’.

Viewing ourselves as a ‘body-mind in a context’, we see that local conditions define how we must behave in order to survive. Language in this sense is a cultural tool that enables us to fit our ecological niche, and do so coherently as a social group. Since in biological terms our mind, emotions and physical sensationsare all the language of a simultaneous, single system, our speech enables us to articulate how this ‘body-mind’, relates to its environment.

I am there, therefore I feel. (At least, I think I can…)

What questions does this allow us to ask about language?

Chomsky suggests that the rules of our language are ‘innate’, arising from our genetics in a predetermined manner, like a body organ. In contrast, the biological evidence, along with Everett’s fieldwork with the Pirahã, suggests instead that the physical structure of our vocal tract, our fine motor control, and our capacities to think in sequences and in symbolic ideas arose as a whole integrated body-mind system.

This combined set of characteristics provided the proto-language function which became refined over evolutionary time into our current communication capacity. This speaking capacity enabled our ancestors to transmit information and behaviours culturally, without directly involving our genetics. Our language function allows us to quickly and flexibly adapt our behaviour to our circumstances.

So: Darwin: 1, Chomsky: 0?

There is however an ‘innate organ’ in the body that makes structured language possible; our brain. It enables us to receive and process our sensory experiences, think intentionally, connect meaning to objects, link ideas, and evaluate memories. To use language, we must be able to perform these cognitive actions, although they are not exclusive to our ability to speak.

Our consciousness allows us to build an internal world in which we use language to define what we think, and to direct these thoughts towards others and back to ourselves. And in this integrated view, where our inner ‘self-talk’ and outer shared speech are part of the same process, Noam Chomsky’s idea of language as a universal innate human mechanism seems to find a home.

Perhaps: Darwin: 1, Chomsky + Darwin = >1

What are we able to say to ourselves about language?

The legend of the ‘Tower of Babel’ portrays the diversity of human languages as a curse. Yet each language is a cultural expression of values, arising in a specific context and anchoring its speakers into a set of attitudes and behaviours which adapt them to their environment. Around the globe, our ecological settings are varied and diverse. According to Daniel Everett, our cultural habits and traditions, transmitted through language, collectively ‘fit’ us to this local ecology with exquisite precision. In evolutionary survival terms, this is a huge strength.

So what can we say about language?

– It is at once physical and embodied, yet held outside of ourselves in our culture. It is symbolic, emotional, moving, fixed into iconic forms, generalised, specific, and allows us to articulate our internal and external awareness.

– Its form and content, rules and structures are mimicked and learned, yet are also dynamic, constantly being revised and re-drafted as we interact with each other.

– It has evolved through our biology, and is still evolving, remodelling itself to each location, age and culture, whilst holding ideas steady and focussing and fixing our thoughts on specific details.

– It is the way we both define our understanding and code meanings. It is made possible by the way in which we break out of old ways of understanding and find new meanings.

– It uses physical movement to transmit information and reveal feelings and emotions. Observing these movements re-creates that other speakers’ reality in the body-mind of the listener.

– It can adapt itself to any channel, transmitting messages through tones, gestures, syllables, drum rhythms, dots and dashes, touch, or written words.

– It has enabled us to adapt our collective behaviour to fit almost every habitat on earth, and continues to be the means by which we organise ourselves to collectively expand beyond our current limits.

In short, language is a cultural tool, made by us and moulded to our needs. It unites us as a species, and is a vehicle through which we express our uniqueness and diversity. And it enables us to tell ourselves the greatest story ever told.

Our story.

Text copyright © 2015 Mags Leighton. All rights reserved.

References

Cavalli-Sforza, L.L. (1994)  The History and Geography of Human Genes. Princeton University Press.

Chomsky, N. (1957)  Syntactic Structures.  Mouton de Gruyer.

Chomsky, N. (2009, 18th August); live interview.

Corballis, M.C. (2009)  The evolution of language.  Annals of the New York Academy of Sciences1156, 19-43.

Corballis, M.C. (2010)  Mirror neurons and the evolution of language.  Brain & Language 112, 25-35.

Desmond, J. (1997)  Embodying difference; issues in dance and cultural studies In Meaning in Motion: New Cultural Studies of Dance (J. Desmond, ed.), pp. 29-54  Duke University Press.

Dunn, M. et al. (2011)  Evolved structure of language shows lineage-specific trends in word-order universals.  Nature 473, 79–82.

Everett, D. (2008)  Don’t sleep, there are snakes.  Profile Books Ltd.

Everett, D. (2012, paperback edition 2013)  Language, the cultural tool.  Profile Books Ltd.

Everett, D. (2012)  There’s no such thing as universal grammar – interview by Robert McCrum for the Observer Newspaper, 25th March 2012.

Fitch, W.T. (2010)  The Evolution of Language. Cambridge University Press.

Ghazanfar, A.A. (2013)  Multisensory vocal communication in primates and the evolution of rhythmic speech.  Behavioural Ecology and Sociobiology 67, 1441-1448.

Greenberg, J.H. (1963)  Some Universals of Grammar with Particular Reference to the Order of Meaningful Elements In Universals of Grammar ( J.H. Greenberg, ed.) pp. 73–113.  MIT Press.

Hauser, M., Chomsky, N., and Fitch, T. (2002)  The faculty of language: what is it, who has it, and how did it evolve.   Science 198, 1569-79.

King, S.L. and Janik, V.M. (2013)  Bottlenose dolphins can use learned vocal labels to address each other.  Proceedings of the National Academy of Sciences, USA 110, 13216-13221.

Levinson, S. and Evans, N. (2010)  The myth of language universals; language diversity and its importance for cognitive science.  Behavioural and Brain Sciences 32, 429-448.

Lieberman, P. (1998)  Eve Spoke; Human Language and Human Evolution.  Norton.

Lieberman, P. (2006)  Towards an evolutionary biology of language. Harvard University Press.

MacNeilage, P. (2006)  The Origin of Speech. Oxford University Press.

Smith, E.A. (2010)  Communication and collective action; language and the evolution of human cooperation.  Evolution and Human Behaviour 31, 231-245.

Suddendorf, T. and Corballis, M.C. (2007)  The evolution of foresight: what is mental time travel, and is it unique to humans?  Behavioral and Brain Sciences 30, 299-351.

Tomlin, R. (1986)  Basic Word Order: Functional Principles.  Croom Helm.

“Mirror, mirror on the wall,
who is the fairest of them all?”

“Fair as pretty, right or true;
what means this word ‘fair’ to you?
Fair in manner, moods and ways,
fair as beauty ‘neath a gaze…
Meaning is a given thing.
I cannot my opinion bring
to validate your plain reflection!
You must make your own inspection.”

---

Mirrors shift our perspective, enabling us to see ourselves directly, and reflect ideas back to us symbolically.  But how do we really see ourselves?

Quite recently, neuroscientists discovered a new type of nerve cell in the brains of macaques which form a network across the primary motor cortex, the brain region controlling body movements.  These nerves are intriguing; they become active not only when the monkey makes purposeful movements such as grasping food, but also when watching others do the same.  As a result, these cells were named ‘mirror neurons’.

In monkeys and other non-human primates, these nerves fire only in response to movements with an obvious ‘goal’ such as grabbing food.  In contrast, our mirror network is active when we observe any human movement, whether it is purposeful or not.  Our brains ‘mirror’ the actions of ourselves and others’ actions, from speaking to dancing.

However it is to interpret what function these cells are performing.  Different researchers suggest that mirror neurons enable us to:

– assign meaning to actions;

– copy and store information in our short term memory (allowing us to learn gestures including speech);

– read other people’s emotions (empathy);

– be aware of ourselves relative to others (giving us a ‘theory of mind’, i.e. we have a mind, and the contents of other people’s minds are similar to our own).

Whilst these opinions are not necessarily exclusive, they do seem to reflect the different priorities of these experts.  Their varied interpretations highlight how difficult it is to be aware of how our beliefs and assumptions affect what our observations can and cannot tell us.

What we can say, is that the behaviour of these nerve cells shows that our mirror neuron responses are very different from those of our closest relatives, the primates.

What do we know about mirror neurons from animals?

Researchers at the University of Parma first discovered mirror neurons in an area of the macaque brain which is equivalent to Broca’s area in humans.  This brain region assembles actions into ordered sequences, e.g. operating a tool or arranging our words into a phrase.  Later studies show these neurons connect right across the monkey motor cortex, and respond to many intentional movements including facial gestures.

The macaque mirror system is activated when they watch other monkeys seize and crack open some nuts, grab some nuts for themselves, or even if they just hear the sound of this happening.  Their neurons make no responses to ‘pantomime’ (i.e. a grabbing action made without food present), casual movements, or vocal calls.

Song-learning birds also have mirror-like neurons in the motor control areas in their brains.  Male swamp sparrows’ mirror network becomes active when they hear and repeat their mating call.  Their complex song is learned by imitating other calls, suggesting a possible role for mirror neurons in learning.  This is tantalising, as we do not yet know the extent to which mirror neurons are present in other animals.

 

The primate research team at Parma suggest the mirror system’s role is in action recognition, i.e. tagging ‘meaning’ to deliberate and purposeful gestures by activating an ‘in-body’ experience of the observed gesture.  The mirror network runs across the sensori-motor cortex of the brain, ‘mapping’ the gesture movement onto the brain areas that would operate the muscles needed to make the same movement.

An alternative interpretation is that mirror neurons allow us to understand the intention of another’s action.  However as monkey mirror neurons are not triggered by mimed gestures, the intention of the observed action presumably must be assessed at a higher brain centre before activating the mirror network.

How is the human mirror system different?

Watching another human or animal grabbing some food creates a similar active neural circuit in our mirror network.

The difference is that our nerves are activated by us observing any kind of movement.  Unlike monkeys, when we see a mimed movement, we can infer what this gesture means.  Even when we stay still we cannot avoid communicating; the emotional content of our posture is readable by others.  In particular we readily imitate other’s facial expressions.

As we return a smile, our face ‘gestures’.  Marco Iacoboni and co-workers have shown that as this happens, our mirror system activates along with our insula and amygdala.  This shows that our mirror neurons connect with the limbic system which handles our emotional responses and memories.  This suggests that emotion (empathy) is part of our reading of others’ actions.  As we see someone smile and smile back, we feel what they feel.

Spoken words deliver more articulated information than can be resolved by hearing  alone.  Our ability to read and copy the movements of others as they speak may be how we really distinguish and understand these sounds.  This ‘motor theory of speech perception’ is an old idea.  The discovery of mirror-like responses provides physical evidence of our ability to relate to other people’s movements, suggesting a possible mechanism for this hypothesis.

Further studies suggest that these mirror neurons are part of a brain-wide network made of various cell types.  Alongside the mirror cells are so-called ‘canonical neurons’, which fire only when we move.  In addition, ‘anti-mirrors’ activate only when observing others’ movements.  Brain imaging techniques show that frontal and parietal brain regions (beyond the ‘classic’ mirror network) are also active during action imitation.  It is not clear how the system operates, but in combination we relate to others’ actions through the same nerve and muscle circuits we would use to make the observed movements.  We relate in this way to what is happening in someone else’s mind.

Are mirror neurons our mechanism of language in the brain?

Mirror-like neurons activate whether we are dancing or speaking.  Patients with brain damage that disrupts these circuits have difficulties understanding all types of observed movements, including speech.  This suggests that we use our extended mirror network to understand complex social cues.

Our mirror neuron responses to words map onto the same brain circuits as other primates use for gestures.  However signals producing our speech and monkey vocal calls arise from different brain areas.  This suggests that our speech sounds are coded in the brain not as ‘calls’ but as ‘vocal gestures’.  This highlights the possible origins of speaking as a form of ‘vocal grooming’, which socially bonded the tribe.

When we think of or hear words, our mirror network activates the sensory, motor and emotional areas of the brain.  We thus embody what we think and say.  Michael Corballis and others consider that mirror neurons are part of the means by which we have evolved to understand words and melodic sounds as ‘gestures’.

What is unclear is how we put meaning into these words.  Some researchers have suggested that mirror neurons anchor our understanding of a word into sensory information and emotions related to our physical experience of its meaning.  This would predict that our ‘grasp’ of the meaning of our experiences arises from our bodily interactions with the world.

Vocal gestures would have provided our ancestors with an expanded repertoire of movements to encode with this embodied understanding.  Selection could then have elaborated these gestures to include visual, melodic, rhythmical and emotional information, giving us a route to the symbolic coding of our modern multi-modal speech.

We produce different patterns of mirror neuron activity in relation to different vowel and consonant sounds, as well as to different sound combinations.  Also, the same mirror neuron patterns appear when we watch someone moving their hands, feet and mouth, or when we read word phrases that mention these movements.

We process word sequences in higher brain centres at the same time as lower brain circuits coordinate the movements required for speech production and non-verbal cues.  Greg Hicock suggests that our speech function operates by integrating these different levels of thinking into the same multi-modal gesture.

Mirror neurons connecting the brain cortex and limbic system may allow us to synchronously process our understanding of an experience with our emotional responses to it.  This allows us to consciously control our behaviour, adapt flexibly to our world, and communicate our understanding to others and to ourselves.

Smoke and mirrors; what do these nerves really show and tell?

The word ‘mirror’ conjures up strong images in our minds.  This choice of name may have influenced what we are looking for in our data on mirror neurons.  However they appear crucial for language.  This and other evidence suggests that our ability to speak and to read meaning into movement is a property of our whole brain and body.

Single nerve measurements show that the mirror neuron network is a population of individual cells with distinct firing thresholds.  Different subsets of these neurons are active when we see similar movements made for different purposes.  This suggests that the network responds flexibly to our experience.

Cecilia Heyes’ research shows that our mirror network is a dynamic population of cells, modified by the sensory stimulus our brain receives throughout life.  She suggests that these mirror cells are ‘normal’ neurons that have been ‘recruited’ to mirroring, i.e. adopted for a specialised role; to correlate our experience of observing and performing the same action.

This gives us a possible evolutionary route for the appearance of these mirror neurons.  Recruitment of brain motor cortex cells to networks used for learning by imitation would create a population of mirror cells.  This predicts that;

i. Mirror-like networks will be found in animals which learn complex behaviour patterns, such as whales. (They are already known in songbirds.)

ii. It should be possible to generate a mirror-like network in other animals by training them to associate a stimulus with a meaning, perhaps a symbolic meaning as in Pavlov’s famous ‘conditioned reflex’ experiments with dogs.

Mirror neurons then, show us that something unusual is going on in our brain.  They reveal that we use all of our senses to relate physically to movement and emotion in others, and to understand our world.  They are part of the system we use to learn and imitate words and actions, communicate through language, and interact with our world as an embodied activity.

However beyond this, we cannot yet see what else they reveal.  Until we do, our conclusions about these neurons must remain ‘as dim reflections in a mirror’.

Conclusions

• Monkey mirror neurons relate the observations of intentional movements to a sense of meaning.
• The human mirror network activates in response to all types of human movements, including the largely ‘hidden’ movements of our vocal apparatus when we speak.
  

  Double rainbow. The second rainbow results from a double reflection of sunlight inside the raindrops; the raindrops act like a mirror as well as a prism.  The colours of this extra bow are in reverse order to the prima... morery bow, and the unlit sky between the bows is called Alexander’s band, after Alexander of Aphrodisias who first described it. (Image: Wikimedia commons)

• These neurons are a component of the neural network that allows us to internally code meaning into our words, and ‘embody’ our memory of the idea they symbolise.
• The mirror network neurons seem to be part of an expanded empathy mechanism that connects higher and lower brain areas, allowing us to understand our diverse experiences from objects to ideas.
• These cells are recruited into the mechanism by which we learn symbolic associations between items (such as words and their meaning).  This shows that it is our thinking process, rather than the cells of our brain, that makes us uniquely human.

Text copyright © 2015 Mags Leighton. All rights reserved.

References

Aboitiz, F & García V R (1997) The evolutionary origin of the language areas in the human brain. A neuroanatomical perspective   Brain Research Reviews 25(3);381-396. doi: 10.1016/S0165-0173(97)00053-2

Aboitiz, F et al.  (2005) Imitation and memory in language origins’ Neural Networks 18(10);1357.. doi: 10.1016/j.neunet.2005.04.009

Arbib, M (2005) ‘The mirror system hypothesis; how did protolanguage evolve?’  Ch 2 (p21-47 ) in Language Origins  -  Tallerman M (ed), Oxford University Press, Oxford.

Arbib, M A (2005) ‘From monkey-like action recognition to human language; an evolutionary framework for neurolinguistics.’  The behavioural and Brain Sciences 2: 105-124

Aziz-Zadeh L et al (2006) Congruent Embodied Representations for Visually Presented Actions and Linguistic Phrases Describing Actions’  Current Biology 16(18); 1818-1823

Braadbaart, L (2014) ‘The shared neural basis of empathy and facial imitation accuracy’  NeuroImage 84; 367 – 375

Bradbury J (2005) ‘Molecular Insights into Human Brain Evolution’. PLoS Biology 3/3/2005, e50  doi:10.1371/journal.pbio.003005

Carr, L.et al. (2003) ‘Neural mechanisms of empathy in humans: A relay from neural systems for imitation to limbic areas’    Proceedings of the National Academy of Sciences of the United States of America  100(9); 5497-5502

Catmur, C. et al (2011) ‘Making mirrors: Premotor cortex stimulation enhances mirror and counter-mirror motor facilitation’  (2011) Journal of Cognitive Neuroscience, 23 (9), pp. 2352-2362.  doi: 10.1162/jocn.2010.21590  http://www.mitpressjournals.org/doi/pdf/10.1162/jocn.2010.21590

Catmur C et al. (2007)  ‘Sensorimotor Learning Configures the Human Mirror System’  Current Biology 17(17) 1527-1531  http://www.sciencedirect.com/science/journal/09609822

Corballis MC (2002)  ‘From Hand to Mouth: The Origins of Language’ Princeton University Press, Princeton, NJ, USA

Corballis MC (2003)  ‘From mouth to hand: Gesture, speech, and the evolution of right-handedness’   Behavioral and Brain Sciences 26(2); 199-208

Corballis, M (2010) ‘Mirror neurons and the evolution of language’ Brain and Language 112(1); 25-35  doi: 10.1016/j.bandl.2009.02.002

Corballis, M.C. (2012) ‘How language evolved from manual gestures’ Gesture 12(2); PP. 200 – 226

Ferrari PF et al. (2003) ‘Mirror neurons responding to the observation of ingestive and communicative mouth actions in the monkey ventral premotor cortex’ European Journal of Neuroscience 17 (8); 1703–1714

Ferrari, P.F. et al (2006)  ‘Neonatal imitation in rhesus macaques’  PLoS Biology, 4 (9), pp. 1501-1508  doi: 10.1371/journal.pbio.0040302  http://biology.plosjournals.org/archive/1545-7885/4/9/pdf/10.1371_journal.pbio.0040302-L.pdf Galantucci, B et al (2006) ‘The motor theory of speech perception reviewed’  Psychon Bull Rev. 2006 June; 13(3): 361–377. PMCID: PMC2746041 NIHMSID: NIHMS136489  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2746041/

Gallesse V et al (1996)  ‘Action recognition in the premotor cortex’  Brain 119:593–609

Gentilucci M & Corballis MC (2006) ‘From manual gesture to speech: A gradual transition’  Neuroscience & Biobehavioral Reviews 30(7); 949-960

Hage, S.R., Jürgens, U. (2006) Localization of a vocal pattern generator in the pontine brainstem of the squirrel monkey  European Journal of Neuroscience 23(3); 840 – 844  doi: 10.1111/j.1460-9568.2006.04595.x

Heyes C (2010) ‘Where do mirror neurons come from?’  Neuroscience and behavioural Reviews 34(4); 575-583  http://www.sciencedirect.com/science/article/pii/S0149763409001730

Heyes CM (2001) ‘Causes and consequences of imitation’ Trends in Cognitive Sciences 5; 245–261

Hickok G (2012)  ‘Computational neuroanatomy of speech production’ Nature Reviews Neuroscience 13, 135-145  doi:10.1038/nrn3158

Jürgens, U (2003) From mouth to mouth and hand to hand: On language evolution Behavioral and Brain Sciences 26(2); 229-230

Kemmerer D and Gonzalezs-Castillo J (2008) ‘The Two-Level Theory of verb meaning: An approach to integrating the semantics of action with the mirror neuron system’  Brain Lang. 112(1);54-76  doi: 10.1016/j.bandl.2008.09.010. Epub 2008 Nov 8.

Keysers C & Gazzola V (2009)  ‘Expanding the mirror: vicarious activity for actions, emotions, and sensations’ Curr Opin Neurobiol. 2009 Dec;19(6):666-71. doi: 10.1016/j.conb.2009.10.006. Epub 2009 Oct 31. Review.

Kohler E et al (2002) Hearing Sounds, Understanding Actions: Action Representation in Mirror Neurons Science297(5582);. 846-848 DOI: 10.1126/science.1070311 

Molenberghs P et al (2012) ‘Activation patterns during action observation are modulated by context in mirror system areas’  NeuroImage59(1); 608–615

Molenberghs P et al. (2012)  ‘Brain regions with mirror properties: A meta-analysis of 125 human fMRI studies’  Neuroscience & Biobehavioral Reviews 36(1); 341-349  http://dx.doi.org/10.1016/j.neubiorev.2011.07.004

Molenberghs P, et al. (2009)  Is the mirror neuron system involved in imitation? A short review and meta-analysis.  Neurosci Biobehav Rev. 2009 Jul;33(7):975-80. doi: 10.1016/j.neubiorev.2009.03.010. Epub 2009 Apr 1.

Mukamel R et al (2010) Single-neuron responses in humans during execution and observation of actions Current biology 20(8); 750–756  http://dx.doi.org/10.1016/j.cub.2010.02.045

Pohl, A et al.  (2013) ‘Positive Facial Affect – An fMRI Study on the Involvement of Insula and Amygdala’  PLoS One 8(8): e69886. doi:10.1371/journal.pone.0069886  PMCID: PMC3749202

Prather, J. F., Peters, S., Nowicki, S., Mooney, R. (2008). "Precise auditory-vocal mirroring in neurons for learned vocal communication." Nature 451: 305-310.

Pulvermüller F (2005) ‘Brain mechansims linking language and action’  Nature Reviews Neuroscience 6:576-582

Pulvermüller F et al (2005) ‘Brain signatures of meaning access in action wordrecognition’  Journal of Cognitive Neuroscience 17;884-892

Pulvermüller F et al (2006)  ‘Motor cortex maps articulatory features of speech sounds’ PNAS 103 (20); 7865–7870  doi: 10.1073/pnas.0509989103

Rizzolatti G & Luppino G  (2001)  ‘The cortical motor system’ Neuron 31:889–901

Rizzolatti G (1996)  ‘Premotor cortex and the recognition of motor actions. Cogn. Brain Res. 3:131–41

Pavlov IP (1927)  ‘Conditioned Reflexes; an investigation of the physiological activity of the cerebral cortex’  OUP, London (republished 2003 as ‘Conditioned Reflexes’ Dover Publications Ltd, NY, USA)

Rizzolatti G, et al (1996)  ‘Localization of grasp representation in humans by PET: 1. Observation versus execution. Exp. Brain Res. 111:246–52

Rizzolatti G, Fogassi L, Gallese V. 2002.  ‘Motor and cognitive functions of the ventral premotor Cortex’  Curr. Opin. Neurobiol. 12:149–54

Rizzolatti G. et al (2001) ‘Neurophysiological mechanisms underlying the understanding and imitation of action’  Nature Reviews Neuroscience,2(9);661-670. doi: 10.1038/35090060

Umilta et al (2001) ‘I know what you are doing.  A neurophysiological study’  Neuron 31:155-165

Pausing on the bank, the lead female gathers her herd, ensuring that she is followed before she plunges in. 

The smaller elephants swim, heads fully submerged.  Others walk at first.  All are snorkel-breathing through their trunks. 

A lone male follows at a distance.  He watches the tribe for a moment before he too enters the water.

---

Elephants are the largest land mammals, and are at home in hot, dry savannah environments. They migrate hundreds of miles in search of food, and when required will cross rivers, lakes, and even undertake marine excursions.  They are surprisingly strong swimmers, and are the only mammals able to snorkel.

This provides a vital evolutionary clue to their past.  Although we associate elephants with dry land, their bodies reveal clear evidence of an aquatic ancestry.

Fossils and DNA put elephants amongst the swimmers

DNA evidence:

Comparing DNA sequencesenables usto build molecular phylogenies, or ‘family trees’, defining the genetic relatedness between species.  These phylogenies show that elephants’ closest living relatives are the fully aquatic sea cows; the dugongs and manatees.

Fossil evidence:

Water molecules (H₂O) contain three isotopes of oxygen; ¹⁶O, ¹⁷O and ¹⁸O.  The lighter forms evaporate more easily, slightly enriching lakes and oceans with ‘heavy’ water.  This then can become incorporated into aquatic plants and the bodies of animals that graze on them.  Analysing the ratio of ‘light’ ¹⁶O to ‘heavy’ ¹⁸O isotopes (i.e. d¹⁸O) in teeth from fossils of the extinct elephant ancestor Moeritherium, show that they contain a higher proportion of ¹⁸O than teeth from land grazing animals.  This tells us that it ate mostly freshwater plants, suggesting its lifestyle was at least semi-aquatic.

Elephant embryos reveal adaptations to breathing under water

Elephants can snorkel because of their elongated trunks, and elastic connective tissues that fill the space between their lungs and their body wall.  Both of these features appear together early in the foetus, suggesting that they were important for survival of the elephant’s ancestors.

As in other large mammals, elephants’ blood pressure is high; this is needed to keep the brain well supplied with oxygenated blood.  Under water, the differences between the pressure of inhaled air (atmospheric; 0mmHg) and the blood pressure in the capillaries (150mmHg) would be enough to rupture blood vessels and the delicate linings of the lung.  Their elastic connective tissues act as shock absorbers, protecting the lungs against such damage.

Elephants’ testes are inside the body like other aquatic mammals

The location of a mammal’s testes is related to temperature.  Excessive heat or cold will kill mammal sperm (including humans), causing sterility.  Hence in puberty, boys’ testes descend into sacs that are slightly cooler than the interior of their bodies.  However aquatic mammals continue to carry their testes inside their abdomen to protect them from cold.  We would expect land-dwelling elephants’ testes to be carried in a scrotum.  Instead, their testes remain inside the body like those of aquatic mammals.

Early in the foetal development of both male elephants and dugongs, an artery develops which directly connects their kidneys and testes.  In contrast, the testes of most land mammals have a less direct connection, allowing them to descend into a scrotum during puberty.  This suggests that like modern dugongs, the elephants’ ancestors lack a scrotum.

Aquatic mammals including dugongs have a plexus of blood vessels that cool their internal testes and uterus through a counter-current heat exchange  mechanism.  Testicular cooling by a blood plexus has not yet been investigated in elephants; however in the absence of heat stress, they maintain a body temperature of around 34-36⁰C, which is similar to the temperature of the scrotum in most other land mammals.

Elephants ears close for swimming

After swimming we often have to shake our head to clear water from our ears.  However elephant ears have a unique sphincter-like muscle that closes the ear canal and prevents water entry when swimming.  This also creates a sealed ‘acoustic tube’, which works with the aerated bones and ‘acoustic fat’ lenses of the elephant skull to amplify low frequency ‘infrasound’.  Dugongs have similar aerated skull bones and fatty deposits; again implying that they share an aquatic ancestor.

Text copyright © 2015 Mags Leighton. All rights reserved.

References

Fowler, M.E. and Mikota, S.K. (eds) (2006) Biology, Medicine, and Surgery of Elephants.  Blackwell.

Gaeth, A.P. et al. (1999)  The developing renal, reproductive and respiratory systems of the African elephant suggest an aquatic ancestry.  Proceedings of the National Academy of Sciences, USA  96, 5555-5558.

Hildebrandt, T. et al. (2007)  Foetal age determination and development in elephants.  Proceedings of the Royal Society of London, B 274, 323-331.

Johnson, D.E. (1978)  The origin of island mammoths and the Quaternary land bridge history of the Northern Channel Islands, California.  Quaternary Research 10, 204-225.

Johnson, D.E. (1980)  Problems in the land vertebrate zoogeography of certain islands and the swimming powers of elephants.  Journal of Biogeography 7, 383-398.

Liu, A.G.S.C. et al. (2008)  Stable isotope evidence for an amphibious phase in early proboscidean evolution.  Proceedings of the National Academy of Sciences,USA 105, 5786-5791.

McKenchie, A.E. and Mzilikazi, N. (2011)  Heterothermy in Afrotropical mammals and birds: a review.  Integrative and Comparative Biology 51, 349-363.

O’Connell-Rodwell, C.E. (2007)  Keeping an ear to the ground: seisemic communication in elephants.  Physiology  22, 287-294.

Poulakakis, N. et al. (2006)  Ancient DNA forces reconsideration of evolutionary history of Mediterranean pygmy elephantids.  Biology Letters 2, 451-454.

Poulakakis, N. and Stamatakis, A. (2010)  Recapitulating the evolution of Afrotheria: 57 genes and rare genomic changes consolidate their history.  Systematics and Biodiversity 8, 395-408.

Seiffert, E.R. (2007)  A new estimate of Afrotherian phylogeny based on simultaneous analysis of genomic, morphological and fossil evidence.  BMC Evolutionary Biology 7, 224.

Springer, M.S. et al. (2004)  Molecules consolidate the placental mammal tree.  Trends in Ecology and Evolution 19, 430-438.

Weissenbrock, N.M. et al. (2012)  Taking the heat: thermoregulation in Asian elephants under different climatic conditions.  Journal of Comparative Physiology, B 182, 311-319.

West, J.B.  Why doesn’t the elephant have a pleural space?  Physiology 17, 47-50.

West, J.B. et al. (2003)  Fetal lung development in the elephant reflects the adaptations required for snorkelling in adult life.  Respiratory Physiology and Neurobiology 138, 325-333.

West, J.B. (2001)  Snorkel breathing in the elephant explains the unique anatomy of its pleura.  Respiration Physiology 126, 1-8.