Originally published 9 May 2000
Here’s a sentence from a report on the evolution of language in a [2000] issue of Nature:
“A challenge for evolutionary biology, therefore, is to provide a detailed mathematical account of how natural selection can enable the emergence of human language from animal communication.”
A lovely, complex sentence of the kind we used to diagram in high school.
I doubt if kids diagram sentences any more, but I loved diagramming. If nothing else, it gave us a sense of how a manageable number of grammatical rules (syntax) could give rise to an endless variety of communications.
What a thing is language. Start with a bunch of noises — vowels and consonants; three or four dozen will do nicely. String them together into words and you have enough combinations to have a verbal expression for millions of different people, places, things, and actions. A babe is born into the world knowing nary a word. By age 2, she will have a few hundred words at her command. An adult might have a working vocabulary of tens of thousands of words.
But even then, we don’t go around grunting single words. We put words together into meaningful sentences using the rules of syntax. And suddenly the number of possible utterances becomes essentially infinite. Hop on Pop is a possibility. So is the Holy Bible or Finnegans Wake.
Where did it all come from? When and where did language evolve? Chimps and gray parrots can be taught to communicate in a pared-down version of human language, but the difference between human speech and the most sophisticated natural animal communication is as different as day and night.
No animal communication except our own is syntactic, or so it seems. The territorial calls of birds, the wiggle dance of bees, and the mysterious vocalizations of whales and dolphins are the best we get in non-human nature. Yet the language of even the most “primitive” human culture is as complex as modern English. Clearly, language took a big leap forward as the human brain exploded in size and complexity. Like all humans on the planet, all spoken tongues can be traced back to a common source.
The fact that all human languages have grammatical similarities suggests, as Chomsky observed, an innate correspondence between language and the brain. But whether the acquisition of language drove development of the brain, or a bigger, more complex brain was a prerequisite for syntactic language is a question no one can yet answer.
Can language be explained in evolutionary terms? That’s the question asked by Martin Nowak, Joshua Plotkin, and Vincent Jansen in the Nature article. Their method is mathematical but their conclusion is simple: Natural selection will favor the development of syntactic communication when the number of “relevant communication topics” surpasses a certain minimum number.
By “relevant communication topics” the researchers mean anything in a speaker’s environment that confers a survival advantage if you can talk about it. “The lion is lurking in the grass” might be such a message, and it is easy to see how accurate communication of this message would give the speaker and his listener an edge.
But what made our hominid ancestors’ environment more complex — more “relevant communication topics” — than that of jackals, dolphins, or gray parrots? Surely other species experience just as many threats to survival, maybe more. Our authors say: “Presumably the increase in the number of relevant communication topics was caused by changes in the social structure.” Which seems to say exactly nothing by way of explanation. We are right back to the chicken and the egg: Did language drive social structure or was it the other way around?
Nowak, Plotkin, and Jansen show how syntactic language might have evolved, but we are left with the mystery of why it evolved (presumably) uniquely for the human species. Something truly wonderful happened in the East African grasslands a few million years ago — the appearance of big, complex brains articulating a sophisticated repertoire of combinatorial sounds — and it seems to have happened all of a piece.
It is easy enough to understand the evolutionary pressures that caused our ancestors to say “The lion is lurking in the grass” or “There’s a nice source of flinty stones just beyond the hill,” but where, for heaven’s sake, did “The sunset is beautiful” come from? And what dynamic of natural selection conferred upon one species among all the others the ability to say:
She walks in beauty, like the night Of cloudless climes and starry skies, And all that's best of dark and bright Meet in her aspect and her eyes?
