SSS 2010-05-04

（单词翻译）

This is Scientific American's Sixty-Second Science. I'm Christopher Intagliata. Got the minute?

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.

Thanks for your minutes for Scientific American Sixty Second Science. I'm Christopher Intagliata.