60秒科学:猛犸缘何可以生存于冰期?

A couple million years ago, mammoths migrated north from Africa to colonize² Eurasia. Sometime around then a massive ice age kicked in—and it was stay warm or die. So their tails and heat-shedding ears shrunk, and they grew thick coats of oily fur. 

But if you're out in the cold all day you also need some biochemical adjustments. Hemoglobin is the protein in red blood cells that delivers oxygen to your tissues. And it doesn't off-load oxygen well at low temperatures; it just clings to it more tightly. So mammoths solved that problem by evolving hemoglobin that releases oxygen more easily in the cold. That’s according to a study published in the journal Nature Genetics. 

Researchers got the DNA³ that codes for hemoglobin from a 43,000-year-old mammoth¹ specimen⁴. They then used E. coli bacteria to produce actual mammoth hemoglobin. Then they compared mammoth hemoglobin to that of their living cousins, Asian elephants, at 37, 25 and 10 degrees Celsius⁵. Due to just a few key structural⁶ changes, mammoth hemoglobin can release oxygen more readily at cold temperatures. Which was just the thing to help mammoths keep their cool.

—Christopher Intagliata
 

1 mammoth   

n.长毛象；adj.长毛象似的，巨大的

参考例句：

• You can only undertake mammoth changes if the finances are there.资金到位的情况下方可进行重大变革。
• Building the new railroad will be a mammoth job.修建那条新铁路将是一项巨大工程。

2 colonize   

v.建立殖民地，拓殖；定居，居于

参考例句：

• Around 700 Arabs began to colonize East Africa.公元700年阿拉伯人开始把东非变为殖民地。
• Japan used to colonize many countries in Asia.日本曾经殖民过许多亚洲国家。

3 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
• Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

4 specimen   

n.样本，标本

参考例句：

• You'll need tweezers to hold up the specimen.你要用镊子来夹这标本。
• This specimen is richly variegated in colour.这件标本上有很多颜色。

5 Celsius   

adj.摄氏温度计的，摄氏的

参考例句：

• The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
• The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。

6 structural   

adj.构造的，组织的，建筑（用）的

参考例句：

• The storm caused no structural damage.风暴没有造成建筑结构方面的破坏。
• The North American continent is made up of three great structural entities.北美大陆是由三个构造单元组成的。