Under pressure

Dr Warren said that he and his colleagues looked at which genes changed as vocal communication evolved.

To reveal this, the team worked out what the genome of a common ancestor of both birds would look like .

"Then we looked for genes that had changed faster in the zebra finch than we would have expected," said Dr Warren. "This shows that there was a [natural] selection pressure on those genes."

This revealed the steps - the tiny molecular changes within each gene - that were most likely to have been associated with the evolution of vocal communication.

Dr Richard Wilson, director of Washington University's Genome Center and another senior researcher involved in the study said: "Now we can look deep into the genome, not just at the genes involved in vocal learning, but at the complex ways in which they are regulated."

"There are layers and layers of complexity that we're just beginning to see. This information provides clues to how vocal learning occurs at the most basic molecular level in birds and in people."

Dr Warren said that the findings would take the research "into the human realm".

"We can start to look at the structure of those genes in humans with stuttering, autism, Parkinson's Disease and a lot of other neurological disorders [where speech is affected] to see if they're altered in any way."

Dr Carlos Botero, a specialist in animal communication from Duke University in the US said that this work brought us "a little bit closer to understanding the links between genes and behaviour."

Dr Botero, who was not involved in this study, added: "These results should be appealing not only to those interested in the evolution of song or communication but also to anyone who has ever wondered how the tiny little molecules in our genes can ultimately influence what we are and what we are able to do."