Dediu and Levinson's work counters the theory that a single, or very few, genetic change(s) resulted in the acquisition of the capacity for language. Instead, the scientists hold that genes associated with language and culture co-evolved.
"The basic idea," Dediu explained, "is that cultural change is not simply an effect of a better genetic background; culture does not have to wait for biology change, but culture generates new selective pressures to which our biology must adapt, changes in biology that might allow new cultural changes in a co-evolutionary cycle."
The evolution of lactose tolerance and changes to our immune and digestive systems due to farming are all examples.
As for when an individual of any species first communicated in a complex way via sound, it's possible the sound was a whistle, Mark Sicoli, an assistant professor in Georgetown University's Department of Linguistics, told Discovery News. Sicoli studies whistled speech still used in parts of Oaxaca, Mexico.
"Hypothetically, whistled speech could be as old as the earliest languages," Sicoli said, adding that it could even have been a component of proto-language, the precursor of human language used by the earlier hominid species.