Excerpt from Wired's intriguingly--? accurately--? grandly? thought-provokingly-titled article Culture May Be Encoded in DNA:
Normally, male finches learn their complex courtship songs from their uncles and fathers. But if there are no vocal role models around, the song will deviate from the traditional song and be harsh to female finch ears. Each bird, then, must learn from his father or uncles, as they learned from their fathers, and so on--but this can only take us so far down the lineage.
“It’s the classic ‘chicken and the egg’ puzzle,” Mitra said. “Learning may explain how the son copies its father’s song, but it doesn’t explain the origin of the father’s song.”
Mitra’s team wanted to find out what would happen if an isolated bird raised his own colony. As expected, birds raised in soundproof boxes grew up to sing cacophonous songs.
But then scientists let the isolated birds give voice lessons to a new round of hatchlings. They found that the young males imitated the songs--but they tweaked them slightly, bringing the structure closer to that of songs sung in the wild. When these birds grew up and became tutors, their pupils’ song continued to conform, with tweaks.
After three to four generations, the teachers were producing strapping young finches that belted out normal-sounding songs.
[read whole article--includes mp3s of the different generations' songs]