英语听力文摘 English Digest 618、美国人的头越来越大了

 　　Americans’ Heads Are Getting Bigger

 

　　The story of human evolution goes something like this: Millions of years ago, homo sapiens began to evolve from the prehistoric¹ ancestor we share with our monkey cousins. First, we evolved the ability to walk upright. Then we began fabricating more elaborate tools. Finally, around 50,000 years ago, we emerged as more or less fully² modern humans with large, fully human brains. And since then, our craniums and the brains they harbor have stayed pretty much the same.

　　Except that, according to one study, the skulls³ of some Americans have actually grown over the past 120 or so years. Specifically, skulls have become larger by about eight millimeters, or a third of an inch. Which may not sound like much, but the growth theoretically allows for additional brain matter roughly equivalent to the size of a tennis ball.

 

　　Now, before we go any further, we need to deal with a tricky⁴ detail of the study, namely, that the researchers looked almost exclusively at skeletons of white Americans. Why? Because, historically, mainly white Americans had donated skeletons to the collections the researchers studied. So while it may be the case that the skulls of Americans of many ethnicities have grown, the study provides evidence only for one group.

 

　　In any case, it’s not at all clear that larger skulls have translated to larger brains or to greater intellect. It’s also not clear why the skulls the researchers looked at got bigger. American life has changed so much over the past century and a half that it will take years of research to begin to identify possible causes.

 

　　But, nevertheless, the observation is interesting as another detail in the complex story of human evolution.

1 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。

2 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

3 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！

4 tricky   

adj.狡猾的，奸诈的；(工作等)棘手的，微妙的

参考例句：

• I'm in a rather tricky position.Can you help me out?我的处境很棘手，你能帮我吗？
• He avoided this tricky question and talked in generalities.他回避了这个非常微妙的问题，只做了个笼统的表述。