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

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.
What has been generally accepted as the reason for adolescence?
选项 A、To allow humans to become sexually mature.
B、To give us an extended childhood during which to learn.
C、To allow us to grow to our relatively large size, compared with other primates.
D、So that parents will take more care of their children.
答案B
解析 属细节推断题。原文末段首句提到：直到最近，人们最主要的解释还是人的身体发育受到了阻碍，因为大脑要发育，还要学会与人交谈、交往等等与人性有关的复杂的人类行为模式(题干中的has been generally accepted对应原文的the dominant explanation)，所以答案为B。A、C选项与原文不符。D选项答非所问。
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