The Evolution of Language
James R Hurford,
to appear in Discovering Biology, by Paul Insel and Don Ross, published by Prentice-Hall.



Only humans have complex language.  No other animal has such an extensive and expressive communication system.  Human adults typically have vocabularies of around 50,000 different words.  Each of these words is individually learned.  This capacity to learn tens of thousands of words is one thing which makes humans unique in their language ability.  Another thing about language which makes humans unique is our ability to compose long complex sentences, using rules in our heads which we have also learned during childhood.   No other animal species gets anywhere near us, when it comes to complex communication.  This is something of a mystery for evolution, because usually we can see clear continuity between species and their predecessors. 


 At present, there are about 6,000 different languages spoken in the world.  They can be amazingly different; some of them are organized in completely different ways from English.  But any human child from any part of the world can learn any of the world's 6,000 languages, if it starts early enough.  Humans have evolved a very special learning ability, to gain mastery, in just a few years of life, of such large and complex information systems.  Science has not yet discovered in full detail the evolutionary pathways which ended with complex human language, but we are beginning to build up a picture.


When thinking about the evolution of language, it is a mistake to try to ask what was "the first language".  Actual languages change so fast that we have no hope of discovering. for example, what might have been a word for FINGER 100,000 years ago.  It's also wrong to ask "what is the oldest language?", in the same way as it doesn't make much sense to talk about "the world's oldest family".  Almost every language is descended from some ancestor language, and those ancestor languages are descended from other ancestor languages, even further back in time.  (The only languages which don't have obvious ancestors are invented languages like Esperanto, and perhaps creole languages.)  We may suppose that the very earliest languages were less complex than modern languages.  But simple languages don't exist today.  Even ancient dead languages like Latin were just as complex as modern languages, and had comparable vocabularies.  The earliest language of which we have any record is Old Akkadian, dating from around 2500 BC.  It was spoken in Mesopotamia, and is now dead.  The human capacity for language goes much further back than that, probably at least 100,000 years.  We have no records of  language, for most of its existence.  For most of that time, there was no writing, which was only invented very late.  Spoken languages can be just as complex as written languages.  Many fully modern languages, even today, are not yet written down.


By looking at what animals can do, we can get some idea of the conditions which gave rise to our language-using species.  All communication, in humans and other species, is about mind-reading and manipulation.  When we speak, we are usually trying to influence another person in some way.  We are not necessarily trying to take advantage of them in any selfish way, but our communication is usually aimed at being of mutual advantage, at least.  In this sense, we use language to manipulate our social situations.  All higher animals do this to some extent.  Birds, for example, have courtship behaviors, aimed at inducing a partner to mate.  When we are spoken to, we are usually pretty good at figuring out what the speaker intended, even though much of the message was not actually encoded in the words that were uttered; in this sense, we can read other people's  minds.  This is not magic or telepathy, but an ability to draw big inferences from very subtle clues.  Animals vary in their mind-reading abilities.  Not surprisingly, domestic animals can read our intentions better than wild animals, because we humans have bred them to be somewhat like us.  Humans seem to be far superior to other animals in their mindreading and manipulation abilities.  Scientists disagree about whether our nearest relatives, the chimpanzees, have what is called a "Theory of Mind", an ability to envisage what fellow-creatures are thinking.  They certainly aren't as good at it as humans.  So somewhere along the evolutionary track to human language, this mind-reading ability expanded considerably. 


Humans live in larger social groups than other primates.  It has been suggested that the need to bond with more people pushed us toward using language to establish and maintain social contacts, because the earlier method or physical grooming, used by our ape cousins, couldn't stretch to so many individuals.  There would not be enough hours in the day to groom all our friends, so we adopted a quick and easy way of keeping in touch with them, by talking to them, so this theory claims.


Humans are a notably cooperative and altruistic species.  Apart from the social insects, like ants and some bees, humans are individually less selfish toward each other than other animals.  Humans are the only species to have developed complex codes of morality.  The fact that humans have also invented dreadful machines for mass murder doesn't contradict this.  We didn't evolve to consider distant peoples our brothers.  Humans do treat more individuals like brothers (that is, unselfishly, altruistically) than other higher animals do.  This altruism goes along with cooperation, which is orchestrated by language and helps humans to cohere in groups better than other species.  Probably the altruistic, cooperative traits in the human psyche co-evolved gradually with our capacity to express ourselves in language.


Human altruism is linked to our long childhoods.  Humans are born very immature.  Babies need a lot of looking after; they are helpless on their own.  Human babies use this period while they are being looked after to learn a lot of their language.  This long period of dependency is characteristic of humans more than any other species.  The size and variety of human languages stems from  the fact that humans in their early lives have nothing much else to do than learn the language of their community.   After puberty, the human language language-learning ability declines.  This argues for the adaptive value of learning the group's communication system before mating age.  A few unfortunate people who have been deprived of language experience in their early lives have not managed to catch up in later life.


To communicate complex thoughts, you've got to have the complex thoughts in the first place.  How complex are the thoughts of other animals?  Obviously, other animals do think, but not in words.  Many of our own thoughts are also not in words.  We are beginning to realize that  animals can have some quite complex thoughts.  Even creatures not closely related to humans, such as parrots, have been trained to be able to make some quite complicated judgements, but still it is clear that their 'intelligence' is way below human capacity.  Animals don't seem to be naturally intererested in communicating about anything other than their own immediate needs.  We humans, on the other hand, delight in telling tall tales about distant, and often fanciful, people, times and places.


The actual physical machinery for speech, the ear and the vocal tract, have been studied from an evolutionary perspective.  It turns out that our hearing is very similar to that of most other mammals.  Nothing very special has evolved in the human auditory system, probably since the earliest mammals.  On the other hand, the human vocal tract has evolved considerably in the last few million years, and quite probably in the last half million years.  Modern humans have better control of their breathing than our ancestors.  We can tell this from the size of the cavities housing the nerves which activate the chest muscles used in breathing.  These cavities are larger in modern humans than in Homo erectus.   Chimpanzees can be trained to hold their breath, but it is a much harder task for them than it is for us.  Humans also have much finer control over their tongues, cheeks, and larynxes than chimpanzees, who struggle to articulate even to simplest of human syllables.  Human babies, from an early age, can manage to make a great range of different sounds with their mouths.  The human larynx (voice-box) is much lower in the throat than in apes.  This gives the cavity that speech travels through a distinctive two-chamber right-angled shape, which enables us to  rpoduce a wider range of vowel sounds (from 'i'  to 'a' to 'u')  than apes.  All this shaping of the vocal tract is an evolutionary process that has taken place probably mostly within the last million years.  Probably it co-evolved with the other capacities needed for language, like learning large vocabularies, learning complex sentence-making rules, and the accompanying altruistic and cooperative social attitudes.


The human capacity for language is a many splendored thing, involving physical characteristics, such as the vocal tract,  and several quite abstract mental traits, such as a rich conceptual system (for thinking) and social dispositions for mindreading and altruistic manipulation.    Somehow, all this must be coded for in the genes, so that a child brought up in a normal supportive environment will naturally grow to hold a very complex system in its brain.  We have very little idea how our genetic makeup translates into our language ability.  But some progress is being made.  Very recently, genetics has discovered a  site on chromosome 7 which correlates with a hereditary language disorder.  People suffering from this disorder have poor speech and less well developed grammar.  The particular mutation leading to this disorder is at a locus, called FOXP2, in which there have been two amino-acid-changing mutations in the recent history of humans (the last 200,000 years), whereas there have been no such changes in the genetuic histories of gorillas and chimpanzees.