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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.
The key characteristic of adolescence in apes is______.
选项 A、an increase in body size
B、sexual development
C、sudden growth after a period of slow growth
D、apes don’t go through adolescence
答案D
解析 属细节题。原文第二段第六行指出，现在的人类是地球上唯一有青春期的动物，故D为正确答案。其他三个选项均为在第三段中提到的人的特点，所以排除。
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