Birds that sing complex songs give clue to origins of human syntax
By Steve Connor, Science Editor, in Denver
17 February 2003
Parrots, hummingbirds and songbirds - which are able to learn complex, repetitive songs - have provided scientists with a unique insight into the origins of syntax, the rules that govern human speech.
A team of researchers led by Erich Jarvis of Duke University in North Carolina has found the key regions of a bird's brain which enable it to construct and remember the complicated sequences of sounds which make up birdsong.
The learning of songs or calls in the animal kingdom is rare. Only three distantly related types of bird and three types of mammal - humans, bats and cetaceans - are capable of vocal learning, which is regarded as the essential first step in the evolution of human language.
Dr Jarvis told the association's conference that his work on parrots, hummingbirds and songbirds had led to the identification of circuits in the brain's cerebrum called glutamate receptors, which are involved in the transmission of nerve impulses as well as the growth of new nerve connections when the brain is learning a song.
Even though hummingbirds have some of the smallest brains of vertebrates, they are still capable of learning and remembering extraordinarily complex songs.
"The main thing they do with their vocal specialisations is to defend territories and attract mates and the more complex the syntax, the sexier the song," Dr Jarvis said.
"These little songbirds - which are some of the smallest birds around - can do more complex things with their vocalisations than say, a horse, which has a much larger brain. So this tells us what really matters is the presence or absence of a circuit in the brain, regardless of the size of the animal," he said.
"Although it might seem far- fetched, I would not be surprised if these ancient receptors could some day help us to identify the entire system of brain regions for vocal learning and language in humans in a way that hasn't been done before," Dr Jarvis said.
"If it is true that these receptors can be used to identify the human language areas it will help surgeons to localise these brain areas during surgery so that they can learn not to touch them."