2013年4月托福考试辅导：toefl听力之发音训练
You'll recall that in last week's class I talked about how the sounds made by most animals, though sometimes complex, are different from human language. Only in humans do these sounds represent objects and events. Keep in mind that most animals can only repeat their limited utterances over and over again, while humans can say things that have never been said before. Today I want to focus on human language and how it developed. I doubt you'll be surprised when I say that the evolution of language was slow and laborious. There's some reliable evidence that language began with early humans a million and a half years ago. Through the study of the size and shape of brain fossils, scientists have determined that early human brains, like modern brains, have a left hemisphere slightly larger than the right hemisphere. We know that in modern humans, the left hemisphere's the seat of language. We also know that early human brains had a well-developed frontal section, known as Broca's area, which coordinates the muscles of the mouth and throat. It's clear, then, that early humans had a speech apparatus. They could produce any sound that we can. What we don't know is whether early humans used what they had. Since scholars know virtually nothing about prehistoric speech patterns, all they can do is speculate about how language actually originated. Let me give you a brief summary of some of these theories.