Professor John Frink
04-13-2006, 08:03 AM
Commentary
From Squeak to Syntax: Language's Incremental Evolution
By GARY MARCUS
The origin of human language has always been a puzzle. No animal communication system comes close to human language in its power, and by most accounts language has been on the planet less than half a million years, a mere blink of the eye in geological time.
How could this be, if language evolved like any other biological trait? Where is the trail of natural selection? Until recently, there was little direct evidence of language's evolution. Languages don't leave fossils, and while there has never been any dearth of theories explaining why language might have evolved (be it for grooming, gossip or seduction), empirical evidence has been hard to come by.
All that is finally starting to change. The booming science of comparative genomics is allowing researchers to investigate the origins of language in an entirely new way: by asking how the genes that underwrite human language relate to genes found in other species. And these new data provide a fresh example of the power of natural selection.
If language had been built on a completely unprecedented set of genes, Darwin (and his successors) would have a lot of explaining to do. With no more than a few hundred thousand years to play with, a linguistic system that depended on thousands of evolutionarily unprecedented genes would seem impossible. But evolution is about random processes that tinker with old parts, not about engineering new ones.
Most of the genes involved in language have some sort of close and ancient counterpart in other species. As a case in point, consider the first gene to be unambiguously tied to language, known as FOXP2, discovered by Simon Fisher and Anthony Monaco, Oxford geneticists.
Rather than emerging from scratch in the course of human evolution, FOXP2 has been evolving for several hundred million years — in a way that placed it perfectly for evolving a critical role in language acquisition.
Like individual people, genes have family histories, which comparative genomicists are finally in a position to reconstruct. FOXP2's lineage stems from a family of "forkhead" genes (named for a piece of the protein they produce). Forkhead genes have long been in the trade of managing the actions of other genes. (In the parlance of biology, they are "regulatory" genes.)
In the forkhead lineage, many related genes emerged, each with a different function. FOXP2 evolved from a particular set of descendant genes that early in the history of vertebrates began to specialize for controlling muscles.
Participation in motor control in turn placed FOXP2 in a prime position for evolving a role in vocal learning, as it did both in songbirds and in humans. FOXP2 is thus not a gene that was invented purely for the purpose of language, but rather, just as Darwin might have anticipated, a gene that has evolved over time — millions of years — adding new functions in successive generations.
Using the tools of molecular biology, a team of German and British scientists led by Svante Paabo probed further, discovering that the variants of FOXP2 found in other animals are remarkably similar to our own: the difference between the human and mouse version is just three amino acids; between human and chimpanzees, it is only two.
When tiny genetic differences are important — when they correlate with survival — they spread rapidly through the population, and that is exactly what has happened in the case of human FOXP2. Those tiny but critical changes have been inherited by essentially every member of our species, a sure sign of their evolutionary importance. In humans, mutations to the gene lead to a congenital disorder that impairs speech and the control of mouth and facial muscles.
If the case of FOXP2 is typical, what we are left with is a story in which language is a product not of some wholly new set of genes, but a long series of small but powerful evolutionary advances.
This is what Darwin called "descent with modification." An intelligent engineer faced with a brand new problem might start from scratch, but evolution instead rejiggers old parts for new functions.
From the perspective of function, human language is without evolutionary precedent. But from the perspective of biology, human language appears simply to be one more remarkable variation on an ancient set of ancestral themes.
link (http://www.nytimes.com/2006/04/11/science/11comm.html?ei=5087%0A&en=9c0dbb527bd9cdfd&ex=1145073600&pagewanted=print)
From Squeak to Syntax: Language's Incremental Evolution
By GARY MARCUS
The origin of human language has always been a puzzle. No animal communication system comes close to human language in its power, and by most accounts language has been on the planet less than half a million years, a mere blink of the eye in geological time.
How could this be, if language evolved like any other biological trait? Where is the trail of natural selection? Until recently, there was little direct evidence of language's evolution. Languages don't leave fossils, and while there has never been any dearth of theories explaining why language might have evolved (be it for grooming, gossip or seduction), empirical evidence has been hard to come by.
All that is finally starting to change. The booming science of comparative genomics is allowing researchers to investigate the origins of language in an entirely new way: by asking how the genes that underwrite human language relate to genes found in other species. And these new data provide a fresh example of the power of natural selection.
If language had been built on a completely unprecedented set of genes, Darwin (and his successors) would have a lot of explaining to do. With no more than a few hundred thousand years to play with, a linguistic system that depended on thousands of evolutionarily unprecedented genes would seem impossible. But evolution is about random processes that tinker with old parts, not about engineering new ones.
Most of the genes involved in language have some sort of close and ancient counterpart in other species. As a case in point, consider the first gene to be unambiguously tied to language, known as FOXP2, discovered by Simon Fisher and Anthony Monaco, Oxford geneticists.
Rather than emerging from scratch in the course of human evolution, FOXP2 has been evolving for several hundred million years — in a way that placed it perfectly for evolving a critical role in language acquisition.
Like individual people, genes have family histories, which comparative genomicists are finally in a position to reconstruct. FOXP2's lineage stems from a family of "forkhead" genes (named for a piece of the protein they produce). Forkhead genes have long been in the trade of managing the actions of other genes. (In the parlance of biology, they are "regulatory" genes.)
In the forkhead lineage, many related genes emerged, each with a different function. FOXP2 evolved from a particular set of descendant genes that early in the history of vertebrates began to specialize for controlling muscles.
Participation in motor control in turn placed FOXP2 in a prime position for evolving a role in vocal learning, as it did both in songbirds and in humans. FOXP2 is thus not a gene that was invented purely for the purpose of language, but rather, just as Darwin might have anticipated, a gene that has evolved over time — millions of years — adding new functions in successive generations.
Using the tools of molecular biology, a team of German and British scientists led by Svante Paabo probed further, discovering that the variants of FOXP2 found in other animals are remarkably similar to our own: the difference between the human and mouse version is just three amino acids; between human and chimpanzees, it is only two.
When tiny genetic differences are important — when they correlate with survival — they spread rapidly through the population, and that is exactly what has happened in the case of human FOXP2. Those tiny but critical changes have been inherited by essentially every member of our species, a sure sign of their evolutionary importance. In humans, mutations to the gene lead to a congenital disorder that impairs speech and the control of mouth and facial muscles.
If the case of FOXP2 is typical, what we are left with is a story in which language is a product not of some wholly new set of genes, but a long series of small but powerful evolutionary advances.
This is what Darwin called "descent with modification." An intelligent engineer faced with a brand new problem might start from scratch, but evolution instead rejiggers old parts for new functions.
From the perspective of function, human language is without evolutionary precedent. But from the perspective of biology, human language appears simply to be one more remarkable variation on an ancient set of ancestral themes.
link (http://www.nytimes.com/2006/04/11/science/11comm.html?ei=5087%0A&en=9c0dbb527bd9cdfd&ex=1145073600&pagewanted=print)