美国科学60秒 SSS 2013-02-18
时间：2018-12-24 作者：英语课 分类：Scientific American(二)月
英语课
A lot of people have had impacted third molars. Third molars produce a lot of chronic 1 pain.
Alan Mann, a Prinston University physical anthropologist 2 at the annual meeting of the American Association for the Advancement 3 of Science in Boston on February 15.
Some thousands of years ago, there was a random 4 mutation 5. It suppressed the calcification 6 of the third molar, a wisdom teeth. So many of you, and many of your children, have grown to adulthood 7 without the apperance of third molars. Now that particular mutation has increased in frequency so that in some populations more than 40% people have one or more absent third molars. So you might ask the question: How did that develop because obviously you have an apparent third molar if you follow survival of the fetus 8, then you are gonna fall over holding your mouth and dying in agony.
Reproduction of the fetuses 9 – what is it all about? In other words, differential reproduction. How will this work? Well, one evening, a person, who has had serious chronic pain with impacted third molars, perhaps of lower third molar, impacting into the mandibular canal(下颌管), causing a lot of pain. The partner comes up and says: How about a bout 10 of reproduction, dear? And the person says: Not tonight, dear, my jaws 11 are killing 12 me.
That is in fact a revolutionary scenario 13; and because that would produce fewer offspring in those people, the prequency of this feature would increase over time.
1 chronic
adj.(疾病)长期未愈的，慢性的；极坏的
- Famine differs from chronic malnutrition.饥荒不同于慢性营养不良。
- Chronic poisoning may lead to death from inanition.慢性中毒也可能由虚弱导致死亡。
2 anthropologist
n.人类学家，人类学者
- The lecturer is an anthropologist.这位讲师是人类学家。
- The anthropologist unearthed the skull of an ancient human at the site.人类学家在这个遗址挖掘出那块古人类的颅骨。
3 advancement
n.前进，促进，提升
- His new contribution to the advancement of physiology was well appreciated.他对生理学发展的新贡献获得高度赞赏。
- The aim of a university should be the advancement of learning.大学的目标应是促进学术。
4 random
adj.随机的；任意的；n.偶然的(或随便的)行动
- The list is arranged in a random order.名单排列不分先后。
- On random inspection the meat was found to be bad.经抽查，发现肉变质了。
5 mutation
n.变化，变异，转变
- People who have this mutation need less sleep than others.有这种突变的人需要的睡眠比其他人少。
- So far the discussion has centered entirely around mutation in the strict sense.到目前为止，严格来讲，讨论完全集中于围绕突变问题上。
6 calcification
n.钙化
- This may be associated with intraabdominal calcification. 与此同时，腹腔内可能发现钙化。 来自辞典例句
- Peritoneal calcification and pseudocyst are described when perforation occurs. 在发生穿孔的时候可有腹膜的钙化和假囊肿形成。 来自互联网
7 adulthood
n.成年，成人期
- Some infantile actions survive into adulthood.某些婴儿期的行为一直保持到成年期。
- Few people nowadays are able to maintain friendships into adulthood.如今很少有人能将友谊维持到成年。
8 fetus
n.胎，胎儿
- In the fetus,blood cells are formed in different sites at different ages.胎儿的血细胞在不同时期生成在不同的部位。
- No one knows why a fetus is not automatically rejected by the mother's immune system. 没有人知道为什么母亲的免疫系统不会自动排斥胎儿。
9 fetuses
n.胎，胎儿( fetus的名词复数 )
- DNA was extracted from fetuses at mid-gestation, about 10 days past conception. DNA从受孕大约10天后的中期妊娠胚胎中提取。 来自互联网
- Brucellosis is a disease that causes fetuses to abort in cattle. 普鲁士菌病是一种可以导致牲畜胎儿夭折的疾病。 来自互联网
10 bout
n.侵袭，发作；一次(阵，回)；拳击等比赛
- I was suffering with a bout of nerves.我感到一阵紧张。
- That bout of pneumonia enfeebled her.那次肺炎的发作使她虚弱了。
11 jaws
n.口部；嘴
- The antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
- The scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。