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Language and the abstract thinking that makes it happen are foremost among the characteristics that make humans human. But linguists, anthropologists and psychologists cannot agree on the moment in man's evolution when that characteristic appeared, or why.
Last week, in an article published in the journal Behavioral and Brain Sciences, a pair of linguists from Arizona State University turned the language-origin clock back more than two million years and dared to contradict a dearly held theory that man learned to talk because he had something to say.
Upright-walking and talking Homo sapiens, the species to which we belong, made his appearance about 100,000 years ago. His ancestors most likely did not have enough vocal equipment to actually speak, but were they capable of human thought and, consequently, of language?
Wendy K. Wilkins and Jennie Wakefield of ASU claim that the size and shape of earlier human skulls indicate that man may have had the brain configuration for language as early as 2.5 million years ago. And that brain developed not because he had communication on his mind, but as a thoughtful consequence of the evolution of his hands.
Wilkins, who is associate dean of the College of Liberal Arts and Sciences at ASU and an expert in language acquisition, and Wakefield, a doctoral student in speech and hearing science with a background in geology, psychology, zoology and neurolinguistics, track the origin of language to an early human species named Homo habilis who lived 2.5 million years ago. Habilis, unlike his predecessors, was a competent toolmaker and could hit a moving target with a rock or a spear, the researchers note. Scientists now know that those areas of the brain that control fine motor skill are closely tied to those areas identified as the centers of language.
"Our approach is grounded in the biology," says Wakefield, "and we want to say that language is a product of some neurological configuration."
But any attempt to plot the origin of language begs a fight, because it requires crossing into the well-guarded territories of neurologists, psychologists, anthropologists and biologists.
"Linguists by and large have ignored language origin because it's a very controversial topic," says Wilkins. "It's hard to do without talking about what makes humans human and the big philosophical and theological issues you have to get into."
Furthermore, Wilkins points out, archaeologists and biologists don't necessarily share the linguist's notion of what language really is.
Language is more than simple communication. Animals, after all, communicate with each other through a limited series of cries or gestures, and through other behaviors, none of which constitutes language.
Nor is speech synonymous with language; the various sign languages that arise in deaf communities--American Sign Language, for example--are voiceless and yet are natural languages. Early man, in fact, may have used hand signs to communicate.
The narrowest definition of language might be the ability to take a limited set of sounds or symbols and string them together in an infinite variety of utterances, following certain rules--syntax--wired into the brain. In this way, an infinite number of meanings, even abstractions, can be expressed.
Much media attention has been wasted on chimpanzees who are taught sign language so that they can ask for food or toys or comfort. Linguists will not call this language because the chimps still have limited repertoires and don't come up with them on their own in the wild.
Humans, on the other hand, start learning at birth to decipher the subtle differences in nearly identical utterances with totally different meanings. "Saber-toothed tigers are easy to hunt," and "Saber-toothed tigers are eager to hunt," look and sound alike, but we can instantly recognize that in terms of who's doing what to whom, they are opposites. That ability to process abstraction and put information in order distinguishes human brains from ape brains, and without it, there can be no language.
And so what Wilkins and Wakefield were looking for was evidence of when that brain emerged in human evolution.
They spent the better part of five years trolling through the literature on language, brain development and anthropology. Other scientists had concluded that Homo habilis had a larger skull than earlier humans; those scientists had made casts of the insides of the fossilized skulls that suggested that the brains inside were larger, too. From the brain shapes, Wilkins and Wakefield were able to deduce that those parts of the brain that are generally associated with language seemed to be in place.
But they may have developed for reasons that had nothing to do with language.
The fossil record shows that habilis made better tools than his ancestors, including weapons that had to be thrown, and this gave him his evolutionary edge over other creatures.
The hand-eye coordination for making and using such tools required a sophisticated brain, and the brain structures involved were closely interconnected with the brain structures required for language. As the motor skills developed, the researchers believe, then so did the configuration of brain circuits that make language possible.
But not speech. Habilis, evidently, did not have a pharynx or a larynx that permitted speech, leaving him, as one critic put it, "lost in thought, capable of abstract processing and grammatical utterances, but with nothing to say."