SALT LAKE CITY — The development of human language is one of the most important and most mysterious events in the history of Homo sapiens. We humans are the only great ape — the only species anywhere — that is capable of practically infinite expression.
Where did we get it from? How did we get this particular talent? According to some MIT researchers, we got a lot of it from the singing of birds.
It's an idea that goes all the way back to Darwin. According to the authors, the "possibility is the one noted by Darwin in his 'Descent of Man': human language first emerged as 'songs' — prosodic contours and syllable structures like birdsong — which were then grafted onto a separate word system."
The idea is that humans actually combined two kinds of communication found elsewhere in the animal kingdom some 50,000 to 80,000 years ago: a "lexical" layer that conveys meaning and can be arranged to create new meanings, and an "expression" layer that allows a sentence to be infinitely reorganized and convey complex meanings. Typical primate calls that warn of predators resemble the lexical layer, and birdsongs resemble the expressive layer.
Take the sentence, "Jane saw a painting." Lexical layer would be the stuff the sentence is talking about, Jane, a painting, and the act of seeing. But the expressive layer comes into play when we create variations on the sentence using the exact same elements: "When did Jane see the painting?" "The painting was seen by Jane." "Jane sees that painting."
All of these sentences involve the same lexical elements, but they all have subtly different meanings because they are expressed in a different way. There are practically infinite ways to do this.
This higher expressive layer closely resembles birdsongs, where an entire song typically conveys a single message using a melody. But this message can be repeated over and over, combined in different ways, and branch into new variations, depending on the bird species.
Other animals, like bees and primates, use much simpler means: This sound means a snake is coming, this waggle means food is precisely here. Repetition and variation don't really play a part.
The human innovation was to do both.
"It's not a very long step to say that what got joined together was the ability to construct these complex patterns, like a song, but with words," said Robert Berwic, co-author and professor of computational linguistics at MIT.
The researchers acknowledge that they have not proved anything, but empirical studies need to be done to see if birsdsong really did influence our speech.
"It's just a hypothesis," Berwick said. "But it's a way to make explicit what Darwin was talking about very vaguely, because we know more about language now."