题目

The development of bigger brains has long been considered a characteristic of our species' increased intelligence and subsequent dominance (主宰) on this planet. The last two million years of our evolution were marked by a nearly fourfold (四倍的) increase in brain volume. But a growing body of evidence suggests our brains recently changed in an unexpected way: They diminished in size sometime following the end of the last Ice Age.The precise timing of that post-Ice Age brain shrink has remained a mystery until now. A group of researchers led by DeSilva used a mixture of fossil and modern sample data to confirm that this loss of gray matter happened between 3,000 to 5,000 years ago, according to research published in June in the journal Frontiers in Ecology and Evolution. DeSilva's group calculated that human brains had remained roughly the same size in average volume, about 1,450 cubic centimeters, for roughly the past 150,000 years. That average rapidly dropped by around 10%, or up to 150 cubic centimeters, over the course of the last few millennia.DeSilva's group found that not only did the human brain size shrink in general, but also it decreased relative to our body size, suggesting that brain size reduction isn't just a byproduct of our shrinking bodies.Many anthropologists had explained the changes coincided with the appearance of agricultural practices around 10,000 years ago, and a global shift away from hunting and gathering. DeSilva's group point to booming eras for ancient civilizations in North Africa, the Middle East and South America — complex societies that they think may have played a role in the shrinkage.The researchers suggested that perhaps our need to maintain a large brain to keep track of information about food, social relationships, and our environment has also relaxed in the past few millennia because we could store information externally in other members of our social circles and groups. That trend is likely strengthened by our use of books, personal devices and the Internet."Like, computers used to be the size of a room, and now they fit in your pocket, so it is important not to relate brain size to smarts." DeSilva said. （1） What can be known about the human brain size? A . Our brain volume has been keeping increasing. B . The size of human brain has dropped to 150 cubic centimeters. C . Until now, the accurate timing of brain shrink is no longer mysterious. D . Fossils and sample data are used to figure out the exact brain shrink period. （2） Which is not the reason for brain shrinkage? A . Appearance of agriculture. B . Decreased body size. C . Developed human society. D . Improved brain mechanism. （3） What is DeSilva and his group's view on the reduction of human brain size? A . A smaller human brain is less smarter. B . The reduction of human brain size is just a coincidence. C . It is a result of brain's adjustment to social development. D . The shrinkage of human brain relaxed us the need to store information. （4） What is the main idea of the passage? A . Reasons for a smarter brain. B . Brain's mysteries to be revealed. C . The precise timing of brain shrink. D . Brain sizes changing circumstantially. 答案： D B C D

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