Part Ⅰ Reading Comprehension

It's often said that in a city you are never more than 2 metres from a rat. In the north of Scandinavia, in the middle of an Arctic winter, the same might be said of Norway's most famous furry little mammal, the lemming. Every three to four years, when the conditions are right, you could be surrounded by hundreds of lemmings scurrying around in a network of branching tunnels beneath your feet.

    When the population is at its lowest, lemmings will be so thin on the ground that there might be just one in 100,000 square meters. However, in good times the same area could be home to as many as 3000. This dramatic cycling of the population helps account for an enduring ……此处隐藏25451个字…… ons, it can't show exactly whether people died in natural disasters or wars. People turned their attention to archaeological findings and found that there are 400 skeletons in the Danube Valley and 18 of them may suffered from violence, which might be the evidence of war. Skeletons are also found in other areas, but we don't know exactly where the collectors come from. It is impossible to say whether the collectors are from Israel Portugal or Sudan, the evidence left behind is too little for us to know what political changes the ancient collectors experienced, what their beliefs were, and what the rules were for them to launch the war of collecting. But these collectors do have a huge impact on our world.