數(shù)百萬年前，猛犸象從非洲出發(fā)，進(jìn)軍歐亞大陸。就在那時(shí)，冰河時(shí)期來臨了。在冰河時(shí)期惡劣的氣候條件下，體型龐大的猛犸象是如何應(yīng)對這樣的環(huán)境的呢？
A couple million years ago, mammoths migrated north from Africa to colonize 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 DNA that codes for hemoglobin from a 43,000-year-old mammoth specimen. 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 Celsius. Due to just a few key structural changes, mammoth hemoglobin can release oxygen more readily at cold temperatures. Which was just the thing to help mammoths keep their cool.
數(shù)百萬年前，猛犸象從非洲出發(fā)，進(jìn)軍歐亞大陸。就在那時(shí)，冰河時(shí)期來臨了，在那種情況下，猛犸象要么想辦法保暖，要么就只有凍死的份兒了。為適應(yīng)環(huán)境，它們的尾巴和用來散熱的大耳朵退化了，毛皮則變得又厚又多脂。 你要是整天呆在寒冷的環(huán)境中，也會需要點(diǎn)生化調(diào)節(jié)。血紅蛋白是人體內(nèi)負(fù)責(zé)輸送氧氣的紅細(xì)胞中的蛋白質(zhì)。但是，在低溫環(huán)境下，血紅蛋白與氧黏著越發(fā)緊密，因此不能很好地卸載氧。當(dāng)初，猛犸象是如何攻克這一難題的呢？它們的血紅蛋白進(jìn)化了——變得更容易在寒冷環(huán)境中卸載氧。（參見《自然-遺傳學(xué)》） 研究人員從一頭43000歲的猛犸象標(biāo)本中獲取了其血紅蛋白DNA，然后用大腸桿菌培養(yǎng)新的血紅蛋白。之后又將該血紅蛋白和與它們形似的亞洲象的血紅蛋白作對比，觀察它們在37℃、25℃和10℃環(huán)境條件下的差異。結(jié)果發(fā)現(xiàn)，正是由于一些關(guān)鍵的構(gòu)造性變異，猛犸象的血紅蛋白能夠更好地在低溫環(huán)境下卸載氧，借此，猛犸象得以在冰河時(shí)期瀟灑生存~