How human speech evolved from birdsong, according to new study Human language incorporates elaborate songs of birds and utilitarian, information-bearing expressions used by other creatures, research claims Humans at some point combined these two pre-existing systems to come up with our uniquely expressive language, it is believed 'The sounds uttered by birds offer in several respects the nearest analogy to language,' Charles Darwin wrote in The Descent of Man, while contemplating how humans learned to speak. Language, he speculated, might have had its origins in singing, which 'might have given rise to words expressive of various complex emotions.' Now researchers from MIT, along with a scholar from the University of Tokyo, say that Darwin was on the right path. A male nightingale singing: Researchers from MIT say that humans combined the elaborate songs of birds and the information-bearing grunts of apes to evolve expressive, meaningful language The balance of evidence, they believe, suggests that human language is a grafting of two communication forms found elsewhere in the animal kingdom: the elaborate songs of birds, and the more utilitarian, information-bearing types of expression seen in a diversity of other animals. 'It's this adventitious combination that triggered human language,' said Shigeru Miyagawa, professor of linguistics in MIT's Department of Linguistics and Philosophy. The idea builds upon Professor Miyagawa's conclusion, detailed in his previous work, that there are two 'layers' in all human languages: an 'expression' layer, which involves the changeable organization of sentences, and a 'lexical' layer, which relates to the core content of a sentence. On the right track: The naturalist Charles Darwin speculated that singing 'might have given rise to words expressive of various complex emotions' His conclusion is based on earlier work by linguists including Noam Chomsky, Kenneth Hale and Samuel Jay Keyser. Based on an analysis of animal communication, and using Professor Miyagawa's framework, the authors say birdsong closely resembles the expression layer of human sentences. The communicative waggles of bees, or the short, audible messages of primates, on the other hand, are more like the lexical layer. At some point, between 50,000 and 80,000 years ago, humans may have merged these two types of expression into a uniquely sophisticated form of language. 'There were these two pre-existing systems,' Professor Miyagawa said. Like apples and oranges that just happened to be put together. These kinds of adaptations of existing structures are common in natural history, notes Robert Berwick, a professor of computational linguistics at MIT, who also contributed to the research. 'When something new evolves, it is often built out of old parts,' he said. We see this over and over again in evolution. Old structures can change just a little bit, and acquire radically new functions. A study has shed light on exactly why tongue-twisters like 'she sells sea shells on the sea shore' are so hard to say. Research showed the brain exercises split-second, symphony-like control to coordinate the tongue, jaw, tongue and larynx to articulate the words we speak. In the same way an orchestra relies on a conductor to coordinate the orchestra's plucks, beats or blows to make music, speaking demands well-timed instructions from the brain to orchestrate these various parts. So, like a conductor's gestures being picked up by the wrong player, when the brain sends messages to muscles near each other that make different sounds, confusion can ensue. Researchers from the University of California, San Francisco, implanted electrode arrays on to the surface of patients' brains. They were then able to record neural activity related to the enunciation of various syllables. They used this information to determine the spatial organisation of the 'speech sensorimotor cortex,' which controls the lips, tongue, jaw and larynx as a person speaks. Findings showed the brain seems to coordinate its articulation of words not by what they sound like, as was previously believed, but by which muscles it needs to move. The data distinguished front-of-the-tongue consonants (like 'sa'), back-of-the-tongue consonants (like 'ga'), and lip consonants ('pa'); vowels split into those that require rounded lips ('ooh') or not ('ee'). 'This implies that tongue twisters are hard because the representations in the brain greatly overlap,' Dr Edward Chang, a neurosurgeon at UCSF, told Nature. 'Sss' and 'Shh', for example, are both recognised by the brain as front-of-the-tongue sounds, so it more easily confuses these than sounds made by different parts of the tongue. And that's why 'she sells sea shells by the sea shore' is more difficult to say than 'he sells sea snails by the green door'. The findings have been published this month in the journal Nature. The new paper, 'The Emergence of Hierarchical Structure in Human Language,' was co-written by Professor Miyagawa, Professor Berwick and Kazuo Okanoya, a biopsychologist at the University of Tokyo who is an expert on animal communication. To consider the difference between the expression layer and the lexical layer, take a simple sentence: 'Todd saw a condor.' We can easily create variations of this, such as, 'When did Todd see a condor?' This rearranging of elements takes place in the expression layer and allows us to add complexity and ask questions. But the lexical layer remains the same, since it involves the same core elements: the subject, 'Todd,' the verb, 'to see,' and the object, 'condor.' 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 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 the researchers, combined these systems. We can communicate essential information, like bees or primates - but like birds, we also have a melodic capacity and ability to recombine parts of our language. For this reason, our finite vocabularies can generate a seemingly infinite string of meanings. 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'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,' Professor Berwick said. Informative: Bees communicate visually, using precise waggles to indicate sources of foods to their peers As they note in the paper, some of the 'striking parallels' between language acquisition in birds and humans include the phase of life when each is best at picking up languages, and the part of the brain used for language. Another similarity relates to an insight of celebrated MIT professor emeritus of linguistics Morris Halle, who, as Professor Berwick puts it, observed that 'all human languages have a finite number of stress patterns, a certain number of beat patterns. Well, in birdsong, there is also this limited number of beat patterns. The researchers acknowledge that further empirical studies on the subject would be desirable. 'It's just a hypothesis,' Professor Berwick said. 'But it's a way to make explicit what Darwin was talking about very vaguely, because we know more about language now.' Professor Miyagawa, for his part, asserts it is a viable idea in part because it could be subject to more scrutiny, as the communication patterns of other species are examined in further detail. 'If this is right, then human language has a precursor in nature, in evolution, that we can actually test today,' he said, adding that bees, birds and other primates could all be sources of further research insight. Meaningful AND expressive: Humans can communicate essential information, like bees or primates - but like birds, we also have a melodic capacity and ability to recombine parts of our language MIT-based research in linguistics has largely been characterized by the search for universal aspects of all human languages. With this paper, Professors Miyagawa, Berwick and Okanoya hope to spur others to think of the universality of language in evolutionary terms. It is not just a random cultural construct, they say, but based in part on capacities humans share with other species. At the same time, Professor Miyagawa noted, human language is unique, in that two independent systems in nature merged, in our species, to allow us to generate unbounded linguistic possibilities, albeit within a constrained system. 'Human language is not just freeform, but it is rule-based,' Professor Miyagawa said. If we are right, human language has a very heavy constraint on what it can and cannot do, based on its antecedents in nature.