LANGUAGE, FOR PROFESSOR Michael Corballis, is the unique function that separates human beings from the rest of the animal world. It has held a particular fascination for the 68-year-old psychologist ever since the discovery in the late 1960s of cerebral asymmetry, which holds that the two sides of the brain perform different functions - the left being responsible for language. Based at the University of Auckland, in New Zealand, Professor Corballis is a research pioneer in cognitive neuroscience and a staunch believer in evolution. Controversially, he thinks that language evolved from manual actions rather than from animal calls. The visiting scholar at Chinese University's United College, last week shed some light on what he called 'a very difficult problem to understand' when he addressed a packed auditorium on the subject of 'Where did language come from'. He has traced the use of language back more than two million years. Prior to that, he said, our ancestors communicated mainly by pointing or making gestures with their hands. The development of speech and grammar, he said, owed much to genetic mutations that caused the human brain to increase in size, thereby enhancing the human capacity to communicate. 'It happened probably from around two million years ago, when behaviour and tool manufacturing became more complex. But it took much longer for human communication to become fully vocal, because a lot of things had to change,' he said, referring to physiological changes that took place, such as the shaping of the human face. Fossil evidence suggests, he said, that fully articulate speech among humans might not have been possible until at some point within the past 200,000 years, perhaps with the emergence of homo sapiens. Based on his evolutionary theory, expounded in The Origins of Language, published in 2002, language was the 'secret weapon' of our ancestors that allowed them to thrive while other hominids died out. 'I don't know which happened first, whether the pressure for complicated language increased the brain size or whether the size increased for some other reasons and then caused language to develop, but it was an evolutionary process,' Professor Corballis said. 'Social bonding was important at the time,' he said. 'There were probably environmental changes that made social activity more important and that would lead to selection for increased brain size.' Evidence has also emerged that the left side of the brain undergoes a growth spurt between the ages of two and four. This is the period during which grammar is acquired, according to Professor Corballis. 'Most four-year-olds know lots of grammar,' he said. 'They pick it up from the environment and also because the left side of the brain is ready for it.' That has provided support for the anecdotal evidence that young children can easily learn two languages through immersion. For older children, learning a second language almost always involves being taught, usually through their native language. 'The later the second language is learned, the more it has to be learned through the first language,' Professor Corballis said. 'If you start teaching a second language at the age of five, they could have learned a certain amount through immersion, but the older they are the more you would have to teach them explicitly using another language.' But all languages share a common, deep structure, he said, echoing the view of linguist Professor Noam Chomsky. 'All languages have word order, use nouns, adjectives and verbs and so forth. Most also use inflections,' he said. 'The basic principles underlying all languages are the same.' But this is where agreement between the two professors ends. Professor Chomsky does not believe that language was born out of an evolutionary process. 'I think he is wrong,' Professor Corballis said. 'I think language was gradually selected because it is advantageous to human beings in terms of producing offspring. People with more language ability had a better chance of survival. And you have to have the genetic make-up to learn language.' He cited, as a sign of evolution, physiological evidence from recent years that only the human brain has incorporated control over speech, whereas in monkeys, for example, the same part of the brain only exercises control over manual gestures. Professor Corballis holds similarly firm views on the origins of humans. 'Evolution is not a mainstream belief among the general public but it is a mainstream thinking of science,' he said. 'There were lots of prominent hominid species before, and we were the only ones that remained. It is our own species that developed full languages - that is why we won.' While people across cultures are capable of learning languages, he said he believed a multi-cultural environment, with people exposed to various languages, improved the likelihood of learning additional languages by means of communication. He added that there was great scope for language to be studied from a multidisciplinary perspective. And he said he was glad this was already emerging as a trend. But perhaps what the scientist most needed to tackle was the challenges to his own research. 'Not everyone believes that language came from gestures,' he admitted. 'Almost everything in language theories is sort of theoretical but you have to keep looking for evidence. That's how science works.'