There are about 5,000 languages spoken in the world today (a third of them in Africa)，but researchers group them together into relatively few families-probably less than twenty.Languages are linked to each other by shared words or sounds or grammatical constructions.The theory is that the members of each language group have descended from one language.In many cases that old language is judged by the experts to have been spoken in surprisingly recent times-as little as a few thousand years ago.

　　The most widespread group of languages today is the Indo­European，spoken by half the world's population.This entire group，ranging from Hindi and Persian to Norwegian and English，is believed to descend from the language of a tribe of nomads (游牧民族) wandering the plains of Eastern Europe and Western Asia (in modern terms centering on the Ukraine) as recently as about 3000 BC.

　　From about 2000 BC people speaking Indo­European languages began to spread through Europe，finally reaching the Atlantic coast and the northern shores of the Mediterranean.They also reached far into Asia-occupying the Iranian plateau and much of India.

　　Another language group，important in the early history of West Asia and still of great importance today，is the Semitic family of languages.These are also believed to come from the language of just one tribal group，possibly nomads in southern Arabia.

　　语篇解读　本文从人们头脑中的词汇、语言的起源和语系分类等角度介绍了语言的历史。

　　5．What makes humans' brains different from animals?

　　A．A set of prearranged signals.

　　B．A cortical speech centre.

　　C．A rational basis.

　　D．A special talent for language.

　　解析：　细节理解题。根据文章第二段It comes from a cortical speech centre...This section of the brain is unique to humans可知应选B项。

　　答案：　B

　　6．The underlined word "descended" in Paragraph 5 probably means________.

　　A．differed B．assumed

　　C．suffered D．developed

　　解析：　词义猜测题。根据画线部分前后文章，及第六段对印欧语系历史的介绍可知descend意为"源于；发展自......"，故选D项。

　　答案：　D

　　7．Compared with the Semitic languages，the Indo­European languages________.

A．have a much longer history