When Darwin wondered at the similarities between birdsong and human speech in the 19th century, he was simply observing their similarities in pattern. But in a newly published paper called The Emergence of Hierarchical Structure in Human Language, three MIT linguists argue that Darwin’s observation was incredibly prescient—in fact, human language may have evolved directly from the communication patterns of birds, bees, and primates.
Building on a foundation laid by the godfather of modern linguistics—Noam Chomsky—the paper’s authors argue that human language takes place on two basic levels. There’s the lexical plane, where we communicate content, and the expressive plane, where grammatical details and sentence structure occur. Fascinatingly, both of these patterns have precedents in the animal world. Birdsong is uniquely expressive, but contains almost no lexical content, while primates, bees, and other animals communicate largely on the expressive plane through simple words or visual cues. At some point, the paper’s authors posit, we humans got the bright idea to combine the two forms of communication, and voilà (sort of)—human language. MIT’s Peter Dizikes explains:
Birdsong lacks a lexical structure. Instead, birds sing learned melodies with what Berwick calls a "holistic" structure; the entire song has one meaning, whether about mating, territory or other things. The Bengalese finch, as the authors note, can loop back to parts of previous melodies, allowing for greater variation and communication of more things; a nightingale may be able to recite from 100 to 200 different melodies.
By contrast, other types of animals have bare-bones modes of expression without the same melodic capacity. Bees communicate visually, using precise waggles to indicate sources of foods to their peers; other primates can make a range of sounds, comprising warnings about predators and other messages.
Humans, according to Miyagawa, Berwick and Okanoya, fruitfully combined these systems. We can communicate essential information, like bees or primates—but like birds, we also have a melodic capacity and an ability to recombine parts of our uttered language. For this reason, our finite vocabularies can generate a seemingly infinite string of words. Indeed, the researchers suggest that humans first had the ability to sing, as Darwin conjectured, and then managed to integrate specific lexical elements into those songs.
It seems that, being the pattern-recognizing creatures that we are, we picked up the metaphorical linguistic building blocks and made something entirely new. "When something new evolves, it is often built out of old parts," says co-author Robert Berwick. "We see this over and over again in evolution. Old structures can change just a little bit, and acquire radically new functions."
[Image: Bird via Shutterstock]