The reason you can speak these words aloud - and chimpanzees can't - may be clearer, thanks to the findings of a new study.
The story starts in 2001, when scientists identified a critical gene found in all vertebrates. Dubbed FOXP2, for "forkhead box protein P2," the "transcription factor" gene's role is to turn the expression of other genes up or down, on or off - the genetic equivalent of a light dimmer.
FOXP2 was discovered during a study of a family in England, three generations of whom suffered from severe speech and language problems. When the family members were found to carry a mutant version of the same gene, it was surmised the gene was important to speech and language development. It was later discovered that the human version of FOXP2 differed by just two amino acids out of a sequence of hundreds, from FOXP2 in chimps, our closest relatives.
Now, a study by scientists at UCLA and Emory University shows human FOXP2 and chimp FOXP2 turn on and off a very different selection of genes. "We knew that the amino acids in the human version of FOXP2 were different from those in the chimp version," says Genevieve Konopka, postdoctoral fellow in neurology at the David Geffen School of Medicine at UCLA and lead author of the study, which was partly funded by NARSAD.
"We knew that the evolution in the gene happened about the time that language occurred" - roughly two hundred thousand years ago. "We wanted to test the hypothesis that the human version of FOXP2 functioned differently from the chimp version." Working with Dr. Daniel Geschwind, Gordon and Virgina MacDonald Distinguished Chair in Human Genetics, and professor of neurology and psychiatry at the UCLA School of Medicine, the team put the two strains of FOXP2 in cell cultures and studied them. If the two-amino-acid difference between human and chimp FOXP2 was really important, then changing them would show some change in function.
"Some genes were more regulated by the human FOXP2, some genes were more regulated by the chimp FOXP2," says Konopka. "It's exciting because we've now identified at least one hundred other genes that might explain why we have language and chimps don't.