Sometimes the biggest finds are the smallest finds. Researchers examining a(26)______of siltstone(粉砂岩)taken from ground along th

Sometimes the biggest finds are the smallest finds. Researchers examining a(26)segment of siltstone(粉砂岩)taken from ground along the Beardmore glacier(冰川)in Antarctica found something(27)unexpected. They found a fly. Well, not exactly a fly. They found a fly(28)fossil—it’s a segment of the protective shell of a fly worm. While the worms arc still growing, they are(29)protected by a thin shell. And where there’s worm shell, there are flies. So what are flies doing in Antarctica? It’s much too cold there for flies. And the closest(30)fly-friendly location, South America, is thousands of miles away.
    Part of the answer is that the fly fossil is(31)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(32)levels were much lower there than they now are. Lower sea levels means wider continents—think of standing on the(33)edge of a beach and having the water pull back.(34)And wider continents means it’s more likely that living things might travel across the gap. Or maybe not. Maybe flies are much older than anyone thought.(35)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.
    Whatever the answer is, something in our understanding of the continents, the seas, or fly evolution has to be fixed.(36)That’s one of the best things about science—a really big change can come from the discovery of something really small.