Talking Gene
PARIS
A couple of tiny sequences on a single gene may help to explain why only humans have the gift of language, while their nearest relatives, the apes, can only grunt or scream.
The minute variations in this key gene became established among Homo sapiens less than 200,000 years ago, says a study published in Nature.
The research is based on a discovery last year that suggests a gene called FOXP2, located on Chromosome 7 of the human genetic code, somehow plays a vital role in the ability to articulate.
Scientists came across a family, several of whose members were unable to speak intelligibly: they lacked the fine control over the larynx, tongue, and mouth to form clear, different sounds. They also had problems with grammar and assembling sentences.
A German-led team took that discovery further. They compared the human FOXP2 with its equivalent in the chimpanzee, gorilla, orangutan, rhesus macaque, and the mouse.
The human version, they found, had three small variations compared with the mouse and orangutan, but only two compared to the other simians.
The chimp, gorilla, and rhesus macaque all had identical FOXP2 genes, with only one difference compared with the mouse, while the orangutan had two differences with the mouse.
The variations are for genetic sequences that control amino acids, one of the building-blocks of protein, say the team, led by Svante Paabo and Wolfgang Enard of the Max Planck Institute for Evolutionary Anthropology in Leipzig.
All the creatures they studied, including humans, once shared common ancestry, which diverged about 70 million years ago. About 4.6 to 6.2 million years ago, the primate lineage then split between humans and chimpanzees. It was at some point during this time that the crucial variant in FOXP2 emerged among humans and spread through evolutionary pressure-hominids who had the ability to communicate had better chances of survival than grunters.
The variant became fully established in the population "during the last 200,000 years of human history, concomitant with or subsequent to the emergence of anatomically modern humans," they say.
But more work is needed to figure out the functions of the FOXP2 proteins and why these substances are so important in language development. Further discoveries about the genetic role in language could lie in store. FOXP2 is the first gene to be spotted that plays a role in this respect.
The subtle but important differences in FOXP2 could shed light on why apes have such poor verbal skills. Chimpanzees and orangutans are good at understanding words and sentences, as well as at learning gestures to get a message across.
AFP
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