The team found that in either social setting, birds of every successive generation imitated their tutor's song but also modified it with small, systematic variations. These improvisations weren't random, however. Accumulating over generations, the introduced changes began to bring the innate, "isolate" song into approximate conformity with the song learned within normal zebra finch "society." (This "cultured" song has been labeled "wild-type" by the scientists.) By the 4th or 5th generation, birds that were descendents of the experimental "isolates" were singing songs that very closely resembled the song sung by birds raised under social conditions in the wild.
"What is remarkable about this result is that even though we started out with an isolated bird that had never heard the wild-type, cultured song, that's what we ended up with after generations," explains Mitra. "So in a sense, the cultured song was already there in the genome of the bird. It just took multiple generations for it to be shaped and come about."
"People have theorized long and hard about how the evolutionary process applies to culture," he says. "This experiment takes culture and puts it into a laboratory setting. We've tested some questions, asked by others over many years, in a mathematically and experimentally crisp manner and come up with a concrete answer."
What the results also mean, according to Mitra, is that the cultured song that's heard in the wild is the product of genes and learning a combination of innate song that would be learned even in isolation, and the effec
|Contact: Hema Bashyam|
Cold Spring Harbor Laboratory