7．You are what you eat．This saying has provided scientists with clues about the diet of hominids（原始人类）-our early relatives of 3million years ago．
Studying carbon atoms（碳原子）locked up in tooth enamel（珐琅质），two researchers argue against the widely held belief that hominids ate little more than fruits and leaves．Sponheimer and Julia Lee-Thorp of the University of Cape Town，South Africa，report their findings in Friday's Science．
There aren't many clues for us to know the life of early hominids．The shape of hominids'teeth offered the first clues．Large and flat-edged with thick enamel，they looked perfect for eating nuts and fruits，different from the sharp teeth one would want to tear into meat with．The first stone tools，which would help in eating meat，didn't appear until about half a million years later．
Scientists have also found marks on hominids'teeth with patterns very similar to those on the teeth of modern-day fruit eaters．Sponheimer and Lee-Thorp tried a new method，looking at the chemical composition（组成） of the tooth enamel．They studied the enamel for the carbon-13．Animals that eat grasses have higher carbon-13levels than those eating fruits and other plants．
What they found was that the teeth to the hominids had an in-between amount of carbon-13，which meant not only they were eating fruits，they were eating a lot of grasses，or animals eating grasses．The lower carbon-13levels could also come from eating certain types of insects．
But there are people who understand differently．Prof．Ungar of the University of Arkansas agrees the study offers new suggestions of hominids diet，but disagrees about the suggestion that meat could explain the lower carbon-13levels．
One suggestion might be true though-take good care of your teeth．In 3million years，a scientist might be using them to figure out what you ate for dinner．
32．Which of the following can be the best title for the text？C
A．Protect Your Teeth．
B．Where the Hominids lived．
C．What the Hominids Ate．
D．The Formation of Teeth Enamel．
33．Before the two scientists'findings，most people thought that hominidsD．
A．used tools to dig grass
B．had sharp teeth
C．lived half a million years ago
D．ate mainly fruits and leaves
34．The two scientists'findings were mainly based on the study aboutC．
A．the shape of hominids'teeth
B．the grasses of 3million years ago
C．the make-up of the tooth enamel
D．the teeth marks of early fruit eaters
35．What is it that Prof．Ungar finds doubtful？B
A．Hominids probably had different diets．
B．Hominids possibly ate grass-eating animals．
C．Hominids were basically fruit and grass eaters．
D．Hominids had lower level of carbon-13in the teeth．
分析 本文是一篇科教类阅读，属于科普文，你是你吃的东西．这句话为科学家们提供了300万年前的早期亲属的人类饮食的线索．本文以此展开，主要讨论了30万前hominids（原始人类）究竟吃什么东西．
解答 32．C．主旨大意题．阅读全文，根据文章内容可知，这篇短文主要讨论了30万前hominids（原始人类）究竟吃什么东西．故选C．
33．D．细节理解题．从第二段第一句话"Studying carbon atoms（碳原子）locked up in tooth enamel（珐琅质），two researches argue against the widely held belief that hominids ate little more than fruits and leaves"可知，在两位科学家的研究之前，大多数人都认为hominids主要吃水果和树叶．故选D．
34．C．细节理解题．根据Sponheimer and Lee-Thorp tried a new method，looking at the chemical composition（组成） of the tooth enamel．可知，两位科学家的发现主要是基于对牙釉质的结构研究．故选C．
35．B．细节理解题．从倒数第二段But there are people who understand differently．Prof．Ungar of the University of Arkansas agrees the study offers new suggestions of hominids diet，but disagrees about the suggestion that meat could explain the lower carbon-13levels．可知，Prof．Ungar不同意肉类可以解释低碳13级的建议．故B正确．故选B．
点评 本文是一篇科教类阅读，题目涉及多道词义猜测题，主旨大意题，细节理解题，推理判断题．做题时学生应仔细阅读原文，把握文章主要内容，联系文章上下文内容并结合所给选项含义，从中选出正确答案，一定要做到有理有据，切忌胡乱猜测．
