critical role, but language ability
is distributed throughout the brain.
A generation ago, it was commonly accepted that language ability is located almost entirely in Broca’s and Wernickes’s areas on the left side of the brain. This view was based upon research into the study of language dysfunction in individuals whose brains had been damaged by trauma or disease. But according to Kenneally, this belief that the left brain is responsible for language is now superseded by the present understanding that language and other higher mental abilities are distributed throughout the brain.
To be sure, once the human brain has matured, the way language function is distributed across the brain is not random. Particular areas take on distinct parts of the overall task of perceiving, understanding, and producing language. But when the parts of the brain that are best suited for language acquisition fail in young children, other parts can sometimes assume the tasks of the damaged regions, restoring a child’s language facility to normal levels. This property of how brain tissue can be re-purposed is called plasticity.
The plasticity of brain organization is not just a human property. The brains of apes change when the creatures have been moved from a standard laboratory setting to a more stimulating environment. An autopsy of a language-trained ape revealed it possessed a brain much larger than average size for its species, and Savage-Rumbaugh maintains that this growth in size was the result of its learning experience. Her research has concluded that primate brains are just as sensitive as humans to small increases in environmental complexity.
While apes in the wild do not sign to one another, and wild parrots do not talk, Kenneally suggests that brain plasticity accounts for their more sophisticated language abilities in captivity, that is, the captive brains grow in response to the increased stimulation provided by constant human contact. In this view, wild animals would derive no benefit from the greatly increased expenditure of mental effort that language requires. There is an enormous difference, Kenneally writes, between being able to speak or not, but this difference may result from circumstance and not from large differences in brain physiology.
She likewise dismisses differences in genetics that purport to account for an innate grammar facility in humans. Much attention has been focused on the discovery that a specific gene, called FOXP2, has a profound effect on language ability. This has prompted speculation, along lines suggested by Chomsky, that the evolution of this gene accounts for the development of language as a mutation that arose without adaptive precedent. Since the emergence of language is synonymous with the appearance of cognitively modern humans between perhaps 50,000 to 80,000 years ago, presumably FOXP2 developed in its present form at that time.
Kenneally rejects this view for several reasons. For example, the human version of FOXP2 is unique to H. sapiens, but biologists have found that the gene is 98 percent the same in humans and songbirds. The avian version of the gene seems to play a significant role in the learning and production of bird song, with the expression of the gene increasing in certain brain areas at the developmental stage when the birds are learning to sing. Mature birds with a greater expression of the gene tend to vary their songs more than others. This indicates that human communication depends on the same genetic foundations as does communication by other animals.
As to the sudden appearance of FOXP2 as a gene for grammar, Kenneally states that Neanderthals, whose last common ancestor with H. sapiens lived at least 400,000 years ago, possessed a version of FOXP2 that was essentially identical to that found in modern humans. Whether Neanderthals could speak or not is unknown, but this is evidence that language ability evolved gradually in the same manner as other cognitive abilities. While some researchers maintain that some genes may exist for the purpose of encoding grammar, Kenneally believes that this idea has been proven false.
Further investigation into the role of FOXP2 may shed light on the evolution of language in an unexpected way. FOXP2 also affects various motor skills, and research has shown that when children acquire language there is an important connection between speaking words and using gestures to add meaning. A consensus appears to be forming among a number of researchers that human language evolved from the volitional use of gestures by great apes for communication.
The work on gesture has demonstrated both a continuum that connects human and ape communication and significant differences between them. In our evolutionary history some individuals must have been born with a greater inclination and ability to collaborate. These individuals were more successful and bred more offspring. Chimpanzees are goal oriented, they cooperate when it is beneficial or expedient to do so. Humans prefer and enjoy collaboration and it is in our desire to connect with others that the symbolic communication of language is found.