【英语时差8,16】玉米是如何演化的？

 Don: Mmm. I'm making corn on the cob for dinner, and my mouth is already watering thinking about those sweet juicy kernels¹!

Yaël: Yum! Hey Don, how did corn evolve? The seeds are all crammed² together on the  cob and wrapped tightly inside the thick husks. Seems impossible for the seeds to disperse³ without a human to peel the husks and separate the kernels.

D: You're right. Corn, or maize⁴, only exists in its modern form because of humans.  Evidence from archaeological and genetic⁵ studies suggests that maize was bred and cultivated by early inhabitants of Mexico as early as ten thousand years ago.

Y: Ten thousand years?! I didn't know people were even farming back then?

D: Not only were they farming, but the early Mesoamericans managed to develop corn  from its grassy⁶ ancestor by selective breeding. Maize was bred from a wild grain called teosinte.

     Teosinte is so unlike modern corn that originally botanists⁷ didn't think the two were even related. An ear of teosinte is only about three inches long, with just five to twelve kernels. Compare that to the corn I'll be munching⁸ tonight, which can have over five-hundred kernels!

     Teosinte kernels also have a "tooth-crackingly" hard shell. But through many generations, ancient Americans selectively bred plants with larger and larger ears, and softer and softer kernels. Now all that is left of that hard shell is the thin tissue  that gets stuck between your teeth when munching a cob of corn.

Y: Wow! Lets tip our hats to the ancient Mesoamericans! Thanks to their sophisticated understanding of plant breeding, we have corn for eating, livestock⁹ feed, cooking oil, ethanol and even making plastics!  

1 kernels   

谷粒( kernel的名词复数 )； 仁； 核； 要点

参考例句：

• These stones contain kernels. 这些核中有仁。
• 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。

2 crammed   

adj.塞满的，挤满的；大口地吃；快速贪婪地吃v.把…塞满；填入；临时抱佛脚( cram的过去式)

参考例句：

• He crammed eight people into his car. 他往他的车里硬塞进八个人。
• All the shelves were crammed with books. 所有的架子上都堆满了书。

3 disperse   

vi.使分散；使消失；vt.分散；驱散

参考例句：

• The cattle were swinging their tails to disperse the flies.那些牛甩动着尾巴驱赶苍蝇。
• The children disperse for the holidays.孩子们放假了。

4 maize   

n.玉米

参考例句：

• There's a field planted with maize behind the house.房子后面有一块玉米地。
• We can grow sorghum or maize on this plot.这块地可以种高粱或玉米。

5 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

6 grassy   

adj.盖满草的；长满草的

参考例句：

• They sat and had their lunch on a grassy hillside.他们坐在长满草的山坡上吃午饭。
• Cattle move freely across the grassy plain.牛群自由自在地走过草原。

7 botanists   

n.植物学家，研究植物的人( botanist的名词复数 )

参考例句：

• Botanists had some difficulty categorizing the newly found plant. 植物学家们不大容易确定这种新发现的植物的种类。 来自辞典例句
• Botanists refer this flower to the rose family. 植物学家将这花归入蔷薇科。 来自辞典例句

8 munching   

v.用力咀嚼（某物），大嚼( munch的现在分词 )

参考例句：

• He was munching an apple. 他在津津有味地嚼着苹果。 来自《简明英汉词典》
• Munching the apple as he was, he had an eye for all her movements. 他虽然啃着苹果，但却很留神地监视着她的每一个动作。 来自辞典例句

9 livestock   

n.家畜，牲畜

参考例句：

• Both men and livestock are flourishing.人畜两旺。
• The heavy rains and flooding killed scores of livestock.暴雨和大水淹死了许多牲口。