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 【26】______ , they were like newborn children, unable to use this 【27】______ tool. Yet once language developed, the possibilities for human kinds future 【28】______ and cultural growth increased. Many linguists believe that evolution is 【29】______ for our ability to produce and use language. They 【30】______ that our highly evolved brain provides us 【31】______ an innate language ability not found in lower 【32】______ . Proponents of this innateness theory say that our 【33】______ for language is inborn, but that language itself develops gradually, 【34】______ a function of the growth of the brain during childhood. Therefore there are critical 【35】______ times for language development. Current 【36】______ of innateness theory are mixed, however, evidence supporting the existence of some innate abilities is undeniable. 【37】______ , more and more schools are discovering that foreign languages are best taught in 【38】______ grades. Young children often can learn several languages by being 【39】______ to them, while adults have a much harder time learning another language once the 【40】______ of their first language have become firmly fixed. 【41】______ some aspects of language are undeniably innate, language does not develop automatically in a vacuum. Children who have been 【42】______ from other human beings do not possess language. This demonstrates that 【43】______ with other human beings is necessary for proper language development. Some linguists believe that this is even more basic to human language 【44】______ than any innate capacities. These theorists view language as imitative, learned behavior. 【45】______ , 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. 【26】