Language is the key feature that distinguishes humankind from animals, yet evolutionary anthropologists know next to nothing about how it came about, when and, most important of all, why. Ancient tools, the first fire and the earliest art have all left some sort of record behind. But the spoken word - which long pre-dated writing - leaves no fossils, bones or stone artefacts. Some evolutionists have supposed that language evolved because it almost had to - a direct and inevitable development from the more basic forms of social communication seen in other primates. This argument says that language developed because it allowed people to speak to one another. But Stanley Ambrose, a palaeoanthropologist at the University of Illinois has a more practical proposition for why language evolved.
Professor Ambrose believes that speaking a language developed hand in hand with tool making. In an article published this week in the journal, Science, he suggests that the manual dexterity needed to make and use the sophisticated stone tools that appeared about 300,000 years ago led to a rapid evolutionary development of the part of the brain used for language. In essence, he likens the intellectual effort of being able to construct a complex tool from a number of everyday objects to the mental task of constructing a grammatical sentence from different words. Once the evolutionary link between tools, hands, brain development and language became established, Professor Ambrose suggests, human cultural evolution took off.
The notion of "preadaptation" is well-established in biology. It says that something as intricately complex as language could come about as a result of some prior development (in this case of the brain) that evolved for another purpose. Terrence Deacon, the evolutionary neuroscientist at Boston University, has described the theory in his 1997 book The Symbolic Species: "Depending on which aspects of language are deemed to be more complex, different prior adaptations are invoked to explain how language became possible. Perhaps it required an increase in intelligence, a streamlining of oral and auditory abilities, a separation of functions to the two sides of the brain, or the evolution of a sort of built-in grammar."
Among our closest living relatives, the apes, there are wide differences in the form of communication they use, ranging from the highly vocal chimp to the almost silent orang-utan. It is easy to see an inevitable evolutionary development of language from these primitive beginnings. "One of the most common views about language evolution is that it is the inevitable outcome of evolution," Professor Deacon says. "Evolution was headed that way, our way. As the only species capable of conceiving of our place among all others, we see what looks like a continuous series of stages leading up to one species capable of such reflections."
This "just so" view of human language says that co-operation between our early ancestors was helped by being able to pass on information quickly and accurately. It also says that being able to connive with others against a third party also played a part in honing and toning our verbal skills. Cheating and lying became as important as telling your friends where to find the best stash of food.
Prof Ambrose believes the driving force for language was not preadaptation but "coadaptation". It was not an evolutionary inevitability but something more tangible. It was, he believes, the innovation of two-handed tool use, where one hand held a "complex" tool and the other held the object it was used against, that became the instrument for language development. It was this that led to the left and right-handedness that is so characteristic of human hand movements, and the distinctive "materialisation" of the human brain, with the left side being critical for both language and complex muscle movements of both the hand and face. …