"Why are humans so smart?" is a question that fascinates scientists. Tadeusz Kawecki, an evolutionary biologist at the Universit

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问题     "Why are humans so smart?" is a question that fascinates scientists. Tadeusz Kawecki, an evolutionary biologist at the University of Fribourg, likes to turn around the question. "If it’s so great to be smart," Dr. Kawecki asks, "why have most animals remained dumb?"
    Dr. Kawecki and like-minded scientists are trying to figure out why animals learn and why some have evolved to be better at learning than others. One reason for the difference, their research finds, is that being smart can be bad for an animal’s health. Learning is remarkably widespread in the animal kingdom. The worms are not born with an innate aversion to the dangerous bacteria. They need time to learn to tell the difference and avoid becoming sick.
    Dr. Dukas hypothesizes that any animal with a nervous system can learn. Even in cases where scientists have failed to document learning in a species, he thinks they should not be too quick to rule it out. "Is it because I’m not a good teacher or because the animal doesn’t learn?" Dr. Dukas asked.
    Although learning may be widespread among animals, Dr. Dukas wonders why they bothered to evolve it in the first place. "You cannot just say that learning is an adaptation to a changing environment," he said. It is possible to adapt to a changing environment without using a nervous system to learn. Bacteria can alter behavior to help their survival. If a microbe senses a toxin, it can swim away. If it senses a new food, it can switch genes on and off to alter its metabolism.
    Learning also turns out to have dangerous side effects that make its evolution even more puzzling. Dr. Kawecki and his colleagues have produced striking evidence for these side effects by studying flies as they evolve into better learners in the lab.
    Dr. Kawecki suspects that each species evolves until it reaches an equilibrium between the costs and benefits of learning. His experiments demonstrate that flies have the genetic potential to become significantly smarter in the wild. But only under his lab conditions does evolution actually move in that direction. In nature, any improvement in learning would cost too much.
    Dr. Kawecki also says it is worth investigating whether humans also pay hidden costs for extreme learning. "We could speculate that some diseases are a byproduct of intelligence," he said. The benefits of learning must have been enormous for evolution to have overcome those costs, Dr. Kawecki argues.
Flies evolve to be smarter only in the labs fundamentally because______.

选项 A、flies can adapt to the environment without learning
B、the cost of learning in the wild is too huge to bear
C、they may get some diseases as a byproduct in nature
D、the lab conditions allow them to learn better

答案B

解析 属信息推断题。文章第六段第二、三句讲到果蝇可以进化得更聪明,但只有在实验室中才会这样。第四句又说到,在大自然中,学习能力的提高会让其付出巨大的代价。因此选项B符合题意。选项A犯了移花接木的错误,是将第四段中的观点拼凑得来的,故错误。选项C同样属于移花接木,疾病是智力的副产品这一观点出现在文章最后一段,而且是在人类身上,与果蝇无关,故错误。选项D较有迷惑性,实验室的条件确实与自然界中不同,但这只是这个问题的表面原因,而不是“fundamental”(根本性的)原因。
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