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VOA常速英语新闻:哺乳动物脑部越大嗅觉越灵?

比目鱼 于2016-07-13发布 l 已有人浏览
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研究人员用计算机断层扫描(CT)来分析在侏罗纪化石层发现的有1.9亿年历史的2只哺乳动物头骨化石。这个研究得出了一个有关生物进化的新观点,就是:可能灵敏的嗅觉要比听觉更重要,同时触觉也很重要。
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Researchers used computed tomography or CT scans to analyze the skulls of 190-million-year-old mammals found in a Jurassic-era fossil bed in China. These tiny critters, co-existed with the giant, meat-eating dinosaurs and probably survived by being nocturnal. 

But to be active in the night, to be nocturnal, you really have to have "very special sensory adaptations. 

Zhe-Xi Luo is a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, and a member of the research team that studied the prehistoric mammal skulls. He says the CT-scans helped the team construct a virtual brain case for two of the ancient mammals. 

In this study we have found that the large brain is becoming larger primarily because the olfactory, or the smelling part of the brain, become very big and also the part related to skin tactile sensation also becomes big. 

Luo says the acute sense of smell and touch that helped mammals survive among the predatory dinosaurs is clearly visible in their ancient anatomy. 

So the new evolutionary biology idea from this study of fossils is, maybe, a capacity to smell very well is as important, even more important than hearing and that the tactile sense probably played a big role too. 

The study finds that the Jurassic-era mammals - including the tiny Hadrocodium, whose skull was smaller than a paper clip - had brains that were two or three times larger than any mammal relatives before them. Hadrocodium has this big head, small mammal, relative to the body size, it has already achieved about the same range of brain size as modern mammals. Luo says he was thrilled to see this impressive brain development in our 190-million-year-old mammalian relatives. An important evolutionary milestone that helped make mammals - and humans among them - one of the Earth's dominant animal classes.

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