VOA标准英语2011--Sense of Smell Jumpstarted Brain Evoluti

Sense of Smell Jumpstarted Brain Evolution

Mammals have much bigger brains than other animals. Scientists aren't sure exactly why, but new research published this week in the journal Science suggests it might have something to do with mammals' acute sense of smell.
Researchers used computed¹ tomography or CT scans to analyze² the skulls⁴ 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 dinosaurs⁵ and probably survived by being nocturnal.
But to be active at night meant the mammals had to have "very special sensory⁶ adaptations," says Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, and a member of the research team that studied the prehistoric⁷ 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 olfactory⁸, or the smelling part of the brain, become very big and also the part related to skin tactile⁹ 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 anatomy¹⁰.
"So the new evolutionary¹¹ 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."
Luo says these Jurassic-era mammals - including the tiny Hadrocodium, whose skull³ 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 was thrilled to see this impressive brain development in our 190-million-year-old mammalian relatives. It's an important evolutionary milestone¹² that helped make mammals - and humans among them - one of the Earth's dominant¹³ animal classes.

1 computed   

adj.[医]计算的，使用计算机的v.计算，估算( compute的过去式和过去分词 )

参考例句：

• He computed that the project would take seven years to complete. 他估计这项计划要花七年才能完成。 来自《简明英汉词典》
• Resolving kernels and standard errors can also be computed for each block. 还可以计算每个块体的分辨核和标准误差。 来自辞典例句

2 analyze   

vt.分析，解析 (=analyse)

参考例句：

• We should analyze the cause and effect of this event.我们应该分析这场事变的因果。
• The teacher tried to analyze the cause of our failure.老师设法分析我们失败的原因。

3 skull   

n.头骨；颅骨

参考例句：

• The skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
• He fell out of the window and cracked his skull.他从窗子摔了出去，跌裂了颅骨。

4 skulls   

颅骨( skull的名词复数 )； 脑袋； 脑子； 脑瓜

参考例句：

• One of the women's skulls found exceeds in capacity that of the average man of today. 现已发现的女性颅骨中，其中有一个的脑容量超过了今天的普通男子。
• We could make a whole plain white with skulls in the moonlight! 我们便能令月光下的平原变白，遍布白色的骷髅！

5 dinosaurs   

n.恐龙( dinosaur的名词复数 )；守旧落伍的人，过时落后的东西

参考例句：

• The brontosaurus was one of the largest of all dinosaurs. 雷龙是所有恐龙中最大的一种。 来自《简明英汉词典》
• Dinosaurs have been extinct for millions of years. 恐龙绝种已有几百万年了。 来自《简明英汉词典》

6 sensory   

adj.知觉的，感觉的，知觉器官的

参考例句：

• Human powers of sensory discrimination are limited.人类感官分辨能力有限。
• The sensory system may undergo long-term adaptation in alien environments.感觉系统对陌生的环境可能经过长时期才能适应。

7 prehistoric   

adj.（有记载的）历史以前的，史前的，古老的

参考例句：

• They have found prehistoric remains.他们发现了史前遗迹。
• It was rather like an exhibition of prehistoric electronic equipment.这儿倒像是在展览古老的电子设备。

8 olfactory   

adj.嗅觉的

参考例句：

• He is to develop a sensor to substitute for the olfactory abilities of dogs.克罗克将研制一种传感器用以代替狗的嗅觉功能。
• Based on these findings, Keller suspects that each person has an olfactory blind spot.根据这些发现，凯勒推断，每个人都有一个嗅觉盲区。

9 tactile   

adj.触觉的，有触觉的，能触知的

参考例句：

• Norris is an expert in the tactile and the tangible.诺里斯创作最精到之处便是，他描绘的人物使人看得见摸得着。
• Tactile communication uses touch rather than sight or hearing.触觉交流，是用触摸感觉，而不是用看或听来感觉。

10 anatomy   

n.解剖学，解剖；功能，结构，组织

参考例句：

• He found out a great deal about the anatomy of animals.在动物解剖学方面，他有过许多发现。
• The hurricane's anatomy was powerful and complex.对飓风的剖析是一项庞大而复杂的工作。

11 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

12 milestone   

n.里程碑；划时代的事件

参考例句：

• The film proved to be a milestone in the history of cinema.事实证明这部影片是电影史上的一个里程碑。
• I think this is a very important milestone in the relations between our two countries.我认为这是我们两国关系中一个十分重要的里程碑。

13 dominant   

adj.支配的，统治的；占优势的；显性的；n.主因，要素，主要的人(或物)；显性基因

参考例句：

• The British were formerly dominant in India.英国人从前统治印度。
• She was a dominant figure in the French film industry.她在法国电影界是个举足轻重的人物。