Why chimps can't talk

Why can humans talk and chimps cannot? Researchers said they have another clue and it lies not simply in the genetic code, but in how the genes function.

Humans and chimpanzees share most of their DNA. Estimates on the percentage range from 98.5% to 95%. Scientists study the differences to find the keys to what distinguishes humans.

A team led by Dan Geschwind at the University of California, Los Angeles, US, looked specifically at a gene called FOXP2, which looks very similar in many animals right up to the time the human lineage split off from the chimpanzee line 4 million to 7 million years ago.

Speech and coordination
FOXP2 is a transcription factor, meaning it affects the activity of other genes. It plays an important role in human speech and affects coordination in other animals such as mice.

Geschwind's team used human and chimpanzee brain tissue to analyse what FOXP2 actually does. Although the DNA code itself is similar, they found subtle differences in two amino acids produced by the gene.

These differences were enough to account for variations in brain structure that may be involved in language, Geschwind's team reported in the journal Nature. They could also account for some of the physical characteristics of the jaw and throat that help humans speak.

FOXP2 differs in humans and chimps
"Earlier research suggests that the amino-acid composition of human FOXP2 changed rapidly around the same time that language emerged in modern humans," Geschwind said in a statement.

"We showed that the human and chimp versions of FOXP2 not only look different but function differently too," added Geschwind, who is currently a visiting professor at King's College London. "Our findings may shed light on why human brains are born with the circuitry for speech and language, and chimp brains are not." – (Reuters Health, November 2009)