Why language is unique to humans ?

U.S. scientists have discovered a single gene which links to human capacity for language and that perhaps can explain why language is unique to humans, according to a study made public Wednesday on the online edition of the journal Nature.

Researchers at the University of California, Los Angeles (UCLA) found that the mystery on why humans can speak lies in a gene called FOXP2. When mutated, FOXP2 can disrupt speech and language in humans.

According to the study, the findings provide insight into the evolution of the human brain and may point out possible drug targets for human disorders characterized by speech disruption, such as autism and schizophrenia.

"Earlier research suggests that the amino-acid composition of human FOXP2 changed rapidly at around the same time when language emerged in modern humans," said Dr. Daniel Geschwind, Gordon and Virginia MacDonald Distinguished Chair in Human Genetics at the David Geffen School of Medicine at UCLA.

"Ours is the first study to examine the effect of these amino-acid substitutions in FOXP2 in human cells," said Geschwind.

"We demonstrated that the human and chimp versions of FOXP2 not only look different but function differently too," said Geschwind.

He said his findings may shed light on why human brains are born with the circuitry for speech and language but chimp brains are not.

In the research, Geschwind and his team used a combination of human cells, human tissue and post-mortem brain tissue of chimps that died of natural causes.

They focused on gene expression, the process by which a gene's DNA sequence is converted into cellular proteins, and discovered that the human and chimp forms of FOXP2 produce different effects on gene targets in the human cell lines.

Geschwind said this suggests that FOXP2 drives these genes to behave differently in the two species.

Genevieve Konopka, first author of the study, said genetic changes between the human and chimp species hold the clues for how human brains developed their capacity for language.

"By pinpointing the genes influenced by FOXP2, we have identified a new set of tools for study how human speech could be regulated at the molecular level," said Konopka.