What does this passage tell us? It tells us why our brains______. [br] [origina

游客2023-09-25  34

问题 What does this passage tell us? It tells us why our brains______. [br]  
Human brains are about three times as large as those of our early ancestors that lived four million to two million years ago, and for years, (11)scientists have wondered how our brains got so big. (12) A new study suggests social competition could be behind the increase in brain size.
    Compared to almost all other animals, human brains are larger as a percentage of body weight. (13) And since the emergence of the first species about two million years ago, the human brain has doubled in size. And when compared to earlier ancestors, (14)such as those that lived four million to two million years ago, our brains are three times as large. For years, scientists have wondered what could account for this increase.
    The three major theories have focused on climate change, the demand of ecology, and social competition.

选项

答案 doubled in size

解析 本题询问自从第一物种出现以后,人类的大脑发生了怎样的变化。根据And since the emergence of the first species about two million years ago,the human brain has doubled in size可知,从二百万年前物种起源到现在,人类的大脑增大了一倍。
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