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