Origins of Human Speech
Kazuo Okanoya, RIKEN
Human speech is a unique biological faculty that enables accurate and transmission and accumulation of information over generations of individuals. Human language can express infinite meanings by combining words according to syntax. Each of these words has corresponding specific meaning but syntax combines
words to enable infinite variety of expressions. No other forms of animal communication systems satisfy all of these characteristics. To understand human uniqueness, we deserve a biological explanation as to the origin of human language. Only recently, however, it became possible to ask such questions due to theoretical and technical advancements to deal human brains and language.
There maybe three ways of thinking to study the biological origin of language. One is to assume language is truly unique to humans and it came to humans suddenly, without going through the process of natural selection (Punctuationist view). Based on such idea, only possible path to understand biology of human language is to study our own brains. One of our speakers, Dr. Sakai, takes such approach. His main focus
is to find the site of brain which deals with purely syntactical processing of recursion (Faculty of Language in a Narrow sense; FLN) by means of noninvasive brain imaging techniques. Another view considers language as a product of natural selection and it gradually gained the level of elaboration our current language have through hominid evolution (Gradualist view). Dr. McCarthy studies fossil evidence to reinforce such idea. Yet another view sees language emerged out of multiple sub-faculties. Each of these might have evolved not for language, but for some other purposes and these sub-faculties were integrated to language. I myself take this pre-adaptationist view. Based on this view, language faculty is dissected into several sub-faculties (Faculty of Language in a Broad sense; FLB) and animal species that might possess one or several of these faculties is selected as a model animal to study neural mechanisms and evolution for each of these sub-faculties.
The estimation of the time when language came might vary according to the positions each researcher takes. In the Punctuationist view, the history of language is equal to that of Homo sapience, which appeared approximately 50,000 years ago. In the Gradualist view, the germ of language could be traced back until when Homo erectus appeared, which dates back as long as 1,500,000 years ago. The Pre-adaptationis view separates biological and cultural origins of language, so for that view language appeared only recently, at about 20,000 years ago.
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