We've blogged here before about birds and cows, among many other non-human purveyors of sound and meaning, having regional dialects, about non-human primates, and dogs, learning and responding to basic human language, and human newborns seeming to cry in a way that reflects their native language. Language acquisition and its evolution are very active areas of research. The results of two studies published last week are further evidence of language abilities that aren't ours alone.
A paper published in the Proceedings of the Royal Society B (Zebra finches exhibit speaker-independent phonetic perception of human speech, Ohms et al., paper published online Dec 2, 2009) reports that finches are able to discriminate between two vowels in single-syllable words, independent of the speaker.
There is an ongoing debate about whether the ability to form phonetic categories that underlie such distinctions indicates the presence of uniquely evolved, speech-linked perceptual abilities, or is based on more general ones shared with other species. We demonstrate that zebra finches (Taeniopygia guttata) can discriminate and categorize monosyllabic words that differ in their vowel and transfer this categorization to the same words spoken by novel speakers independent of the sex of the voices. Our analysis indicates that the birds, like humans, use intrinsic and extrinsic speaker normalization to make the categorization. This finding shows that there is no need to invoke special mechanisms, evolved together with language, to explain this feature of speech perception.And, a report of a long-term study of vocalization among Campbell's monkeys in the Ivory Coast, suggests that these animals are able to combine sounds to make new meaning in response to external events, such as the sighting of predators (Campbell’s monkeys concatenate vocalizations into context-specific call sequences, Ouattaraa et al., PNAS, published online Dec 9, 2009). "These call combinations were not random, but the product of a number of principles, which governed how semantic content was obtained."
The trend seems to be toward a chipping away at specifics that have previously been thought to make human language a singular attribute of our species, or at least as singular as many would fancy it to be. It seems likely that there's no one aspect of our language and perception capabilities that can explain how we alone have the ability to give abstract meaning to sound or to convey completely new ideas between ourselves in the open-ended ways that we do.
Language is another complex trait that can't be explained by reducing it to its many parts -- the use of prefixes, suffixes, the effect of a single gene, our sound discrimination abilities, and so on. Instead, it's an emergent property that flows from what our brain allows us to make of the world, combined with our biological ability to make and detect sound (although, that's clearly secondary and not essential, as the complexity of sign language used around the world demonstrates), and built on a foundation that has been evolving for millions of years. Hundreds or thousands of genes are required for this, as the plethora of mutations in genes that affect cognitive abilities including language clearly show.
This makes sense. Every trait evolves from precursors. Every step of the way we humans are shown not to be unique but to be more a part of the Nature that produced us -- even if, albeit, every species is, almost by definition, unique. It is hubris to think otherwise, be it with respect to language or even consciousness. That doesn't take away in any sense from the interesting question of what humans are and how we got that way -- and why we are as much different from other species as we are.
And, of course, if anything, it is more evidence against those who cling hopefully to the idea that we were specially created outside of Nature rather than evolved within it. Each discovery of the role of environments in molding our basic abilities, or of characteristics we share with other species, even very distant ones, confirms our place in Nature. And it stimulates further interesting research. But it won't lead to easy categorical conclusions.