Language evolved in a leap
Conflicting needs may have driven rapid development of communication.
22 January 2003
PHILIP BALL
Language probably leapt, not crept, from squeaks to Shakespeare, two
physicists have calculated. Human communication, they propose,
underwent a 'phase transition', like solid ice melting to liquid
water.
The richness of human languages is a fine-tuned compromise between
the needs of speakers and of listeners, explain Ramon Ferrer i Cancho
and Ricard Solé of the Universitat Pompeu Fabra in Barcelona. Just a
slight imbalance of these demands prevents the exchange of complex
information, they argue.
So languages between those of present-day humans and the limited
signalling of some animals cannot really exist. There must, at some
point, have been a switch from rudimentary to sophisticated language.
This contrasts with some linguists' view that language evolution was
a gradual affair in which new words accumulated steadily.
Greek or grunt
A language that conveyed all information unambiguously, say Ferrer i
Cancho and Solé, would have a separate word for every thing, concept
or action it referred to. Such a language would be formidably
complicated for the speaker: the green of grass, for example, would
be represented by a totally different word to the green of sea, an
emerald or an oak leaf. But it would be ideal for the listener, who
wouldn't have to work out any meanings from a word's context.
Ideal for the speaker is a language of few words, where simple, short
utterances serve many purposes. The extreme case is a language with a
single sound that conveys everything that needs saying. Some might
suggest that teenagers prefer this kind of minimal-effort tongue that
forces others to figure out what their grunts actually mean.
Ferrer i Cancho and Solé have devised a mathematical model in which
the cost of using a language depends on the balance between these
conflicting preferences1. They calculate the properties of the
lexicon that requires minimal effort for different degrees of
compromise, from exhaustive vocabularies to one-word languages.
They find that the change from one extreme to the other does not
happen smoothly. There is a jump in the amount of communication, from
very little to near-perfect, at a certain value of the relative
weightings of speaker and hearer preferences.
Human languages, say the duo, seem to sit right on this sudden
change. When it happens, the frequency of word usages develops a
distinctive mathematical form, called a power law. The power law
disappears on either side of the communication jump.
It has been known since the 1940s that human languages do indeed show
just this kind of statistical distribution of word usage - the social
scientist George Kingsley Zipf spotted the power-law behaviour. But
it has never been satisfactorily explained before, although Zipf
himself speculated that it might represent some kind of "principle of
least effort".
References
Ferrer i Cancho, R. & Solé, R. V. Least effort and the origins of
scaling in human language. Proceedings of the National Academy of
Sciences USA, published online, doi:10.1073/pnas.0335980100 (2003).
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