听力文摘：南极有苍蝇？

What's a Fly Doing in Antarctica?

南极有苍蝇？

Sometimes the biggest finds are the smallest finds. Researchers examining a segment of siltstone taken from ground along the Beardmore glacier¹ in Antarctica found something unexpected. They found a fly.

有时候，重大发现源于很小的发现。研究人员在南极比尔德莫尔冰川采集回来的一块粉砂岩中意外地发现了苍蝇。

Well, not exactly a fly. They found a fly fossil–it's a segment of the exoskeleton, the protective shell, of a fly larva. While the larvae² are still growing, they are protected by a thin shell. And where there's larval shell, there are flies. So what are flies doing in Antarctica? It's much too cold there for flies. And the closest fly-friendly location, South America, is thousands of miles away.

准确地说，不是苍蝇，而是苍蝇的化石。一块保护幼虫的外骨骼。在薄壳的保护下，幼虫还在发育。幼虫的蛹壳证明了苍蝇的存在。那么，苍蝇怎么会在南极呢？南极冰冷的气候不适宜苍蝇生长啊！反而，最适宜苍蝇生存的地方——南非，却远在几千里之外。

Part of the answer is that the fly fossil is ancient–it was found with a number of other fossilized things that have been dated between three million and seventeen million years old. It's possible that the fly lived during a period when sea levels were much lower there than they now are. Lower sea levels means wider continents –think of standing³ on the edge of a beach and having the water pull back. And wider continents means it's more likely that living things might travel across the gap.

正解可能是因为这块苍蝇的化石和一起发现的其它化石可以追溯到300万到700万年前了。很可能，苍蝇生长的那个时期，海水没有现在那么高，这意味着陆地面积更大。想象自己站在海边，浪打回来。广阔的陆地面积让生物更有可能跨越于大陆间。

Or maybe not. Maybe flies are much older than anyone thought. We know that what we now call Antarctica was once connected to both South America and Australia. But that was around eighty million years ago, and flies aren't thought to be that old.

另种可能是苍蝇在地球上生存的时间比我们想象的还要久远。要知道，现在的南极曾经和南美大陆及澳大利亚大陆是接壤的。但这也是8000万年前的事了，那时候，苍蝇已经在地球上了？

Whatever the answer is, something in our understanding of the continents, the seas, or fly evolution has to be fixed⁴. That's one of the best things about science–a really big change can come from the discovery of something really small.

不管答案究竟是什么，我们所认识的大陆、海洋、苍蝇进化的常识之一要得以修正。这就是科学的妙处，一个小小的发现或许能推翻重大定论。

1 glacier   

n.冰川，冰河

参考例句：

• The glacier calved a large iceberg.冰河崩解而形成一个大冰山。
• The upper surface of glacier is riven by crevasses.冰川的上表面已裂成冰隙。

2 larvae   

n.幼虫

参考例句：

• Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
• The larvae prey upon small aphids.这种幼虫以小蚜虫为食。

3 standing   

n.持续，地位；adj.永久的，不动的，直立的，不流动的

参考例句：

• After the earthquake only a few houses were left standing.地震过后只有几幢房屋还立着。
• They're standing out against any change in the law.他们坚决反对对法律做任何修改。

4 fixed   

adj.固定的，不变的，准备好的；(计算机)固定的

参考例句：

• Have you two fixed on a date for the wedding yet?你们俩选定婚期了吗？
• Once the aim is fixed,we should not change it arbitrarily.目标一旦确定，我们就不应该随意改变。