London: A mutation in a gene might help explain why chimps, our nearest relative, don``t talk, claim scientists.
It is known that when mutated, FOXP2 can disrupt speech and language in humans, and now the study has revealed major differences between how the human and chimp versions of the gene work, perhaps explaining why language is unique to humans.
The findings provide insight into the evolution of the human brain and may point to 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 around the same time that language emerged in modern humans. Ours is the first study to examine the effect of these amino-acid substitutions in FOXP2 in human cells," Nature quoted Dr. Daniel Geschwind as saying.
"We showed that the human and chimp versions of FOXP2 not only look different but function differently too. Our findings may shed light on why human brains are born with the circuitry for speech and language and chimp brains are not," he added.
FOXP2 switches other genes on and off. In the laboratory, researchers scoured the genome to determine which genes are targeted by human FOXP2.
They used a combination of human cells, human tissue and post-mortem brain tissue from chimps that died of natural causes.
The scientists focused on gene expression, and surprisingly found that the human and chimp forms of FOXP2 produce different effects on gene targets in the human cell lines.
"We found that a significant number of the newly identified targets are expressed differently in human and chimpanzee brains. This suggests that FOXP2 drives these genes to behave differently in the two species," said Geschwind.
The research demonstrates that mutations believed to be important to FOXP2``s evolution in humans change how the gene functions, resulting in different gene targets being switched on or off in human and chimp brains.
"Genetic changes between the human and chimp species hold the clues for how our brains developed their capacity for language. By pinpointing the genes influenced by FOXP2, we have identified a new set of tools for studying how human speech could be regulated at the molecular level," said first author Genevieve Konopka.
The discovery will provide insight into the evolution of humans`` ability to learn through the use of higher cognitive skills, such as perception, intuition and reasoning.
The study has been published in the online edition of the journal Nature.