East Africa, one-and-a-half million years ago: a group of women sit with their young children. They are heavy-browed with small

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问题     East Africa, one-and-a-half million years ago: a group of women sit with their young children. They are heavy-browed with small skulls—not quite human, but almost. Some are checking their children for ticks, others teaching them how to dig tubers out of the ground. Not far off, a gaggle of teenage girls lounge under a tree, sniggering and pointing at some young men who are staging fights nearby. The older women beckon: "Come and help us dig out this root—it will make a great meal," they seem to say. But the girls reply with grunts and slouch off, sulkily.
    Could this really have happened? Our immediate ancestors, Homo erectus, may not have had large brains, high culture or even language, but could they have boasted the original teenage rebels? That question has been hotly contested in the past few years, with some anthropologists claiming to have found evidence of an adolescent phase in fossil hominids, and others seeing signs of a more apelike pattern of development, with no adolescent growth spurt at all. This is not merely an academic debate. Humans today are the only animals on Earth to have a teenage phase, yet we have very little idea why. Establishing exactly when adolescence first evolved and finding out what sorts of changes in our bodies and lifestyles it was associated with could help us understand its purpose.
    We humans take twice as long to grow up as our nearest relatives, the great apes. Instead of developing gradually from birth to adulthood, our growth rate slows dramatically over the first three years of life, and we grow just a few centimetres a year for the next eight years or so. Then suddenly, at puberty, growth accelerates again to as much as 12 centimetres a year. Over the following three years adolescents grow an astonishing 15 percent in both height and width. Though the teenage years are most commonly defined by raging hormones, the development of secondary sexual characteristics and attitude problems, what is unique in humans is this sudden and rapid increase in body size following a long period of very slow growth. No other primate has a skeletal growth spurt like this so late in life. Why do we?
    Until recently, the dominant explanation was that physical growth is delayed by our need to grow large brains and to learn all the complex behaviour patterns associated with humanity—speaking, social interaction and so on. While such behaviour is still developing, humans cannot easily fend for themselves, so it is best to stay small and look youthful. That way you do not eat too much, and your parents and other members of the social group are motivated to continue looking after you. What’s more, studies of mammals show a strong relationship between brain size and the rate of development, with larger-brained animals taking longer to reach adulthood. Humans are at the far end of this spectrum.
It is advantageous to look youthful because______.

选项 A、other members of society rarely attack younger looking members
B、young people eat less
C、older members of society do not usually consider younger people to be threats
D、humans have a natural instinct to take care of younger members of society

答案D

解析 属细节题。定位原文末段倒数第三句:这样一来,你吃的又少,父母和其他社会成员都会愿意继续照顾你,D项与此吻合。A项原文未提。B项在文中虽然提到,但不是看上去年轻有好处的原因,属答非所问。C项说年纪大的人并不认为年纪小的人有威胁,与原文不符。
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