在最后一个冰期期间，他们了解到海平面的下降偶尔会产生横跨海峡的陆桥。
They knew that every so often during past ice ages, drops in sea level created a land bridge across the strait.
假设你正在建造一座桥梁，如果工程已经进行到一半，那么客户就决不会说：“天哪，我想这座桥要是建在河流的下一个弯口的话就更加实用了。”
If you are building a bridge that is half completed, the customer is not going to say, "Gee, I think the bridge would be more useful at the next bend in the river rather than over here."
通俗地讲，运用材料力学的弹性拱原理造桥，这种结构就可以将受力点的力分散到桥的每一个横截面上。
Generally speaking, the bridge structure incorporating the flexible arch principle in material mechanics can disperse every point of pressure to the cross-section equally.
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