From childhood to old age, we all use language as a means of broadening our knowledge of ourselves and the world about us. When humans first  16   , they were like newborn children, unable to use this    17    tool. Yet once language developed, the possibilities for human kinds future   18  and cultural growth increased.Many linguists (语言学家) believe that evolution is   19  for our ability to produce and use language. They   20   that our highly evolved brain provides us    21  an innate language ability not found in lower    22    . Proponents (建议者) of this innateness theory say that our   23  for language is inborn, but that language itself develops gradually,  24  a function of the growth of the brain during childhood. Therefore there are critical biological times for language development.Current   25  of innateness theory are mixed, however, evidence supporting the existence of some innate abilities is undeniable.    26  , more and more schools are discovering that foreign languages are best taught in   27   grades. Young children often can learn several languages by being   28  to them, while adults have a much harder time learning another language once the rules of their first language have become firmly fixed.   29  some aspects of language are undeniably innate, language does not develop automatically in a vacuum. Children who have been   30  from other human beings do not possess language. This demonstrates that interaction with other human beings is necessary for proper language development. Some linguists believe that this is even more basic to human language acquisition than any innate capacities. These theorists view language as imitative, learned behavior. In other words, children learn language from their parents by imitating them. Parents gradually shape their child’s language skills by positively reinforcing precise imitations and negatively reinforcing imprecise ones.

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