So competition was fierce. There was also an omnivorous and unsettling new type of predator on the scene, one so perfectly designed for attack that it has scarcely changed in all the long eons since its emergence: the shark. Never would there be a more propitious time to find an alternative environment to water.
于是，竞争很激烈。而且，出现了一种新的无所不吃的、令人不安的捕食者。这种动物的体型完全适用于攻击。自出现以来，它在漫长的历史时期里几乎没有变化。它就是鲨鱼。因此，找一个取代水的环境的最佳时刻终于到了。

Plants began the process of land colonization about 450 million years ago, accompanied of necessity by tiny mites and other organisms that they needed to break down and recycle dead organic matter on their behalf. Larger animals took a little longer to emerge, but by about 400 million years ago they were venturing out of the water, too. Popular illustrations have encouraged us to envision the first venturesome land dwellers as a kind of ambitious fish— something like the modern mudskipper, which can hop from puddle to puddle during droughts—or even as a fully formed amphibian. In fact, the first visible mobile residents on dry land were probably much more like modern wood lice, sometimes also known as pillbugs or sow bugs. These are the little bugs (crustaceans, in fact) that are commonly thrown into confusion when you upturn a rock or log.
大约45000万年以前，植物开始了占领陆地的进程。与其为伴的还有必不可少的小螨虫和其他动物。植物需要它们来为自己分解死去的有机物质。使之再循环。大动物过了更长的时间才出现，但到了大约4亿年以前，它们也大胆地从水里爬了出来。许多通俗插图给我们这样的一种印象：第一批冒险爬上陆地生活的是一种雄心勃勃的鱼——它的样子有点像现代的弹涂鱼。在旱季能从一个水塘跳到另一个水塘，或者甚至是一种完全成形的两栖动物。实际上，陆地上第一批可见的、能四处活动的居民很可能更像现代的潮虫，有时候也被称之为球潮虫或鼠妇。这些都是小虫子（实际上是甲壳纲动物），要是你翻起一块岩石或一根木头，它们常常会惊恐万状。
For those that learned to breathe oxygen from the air, times were good. Oxygen levels in the Devonian and Carboniferous periods, when terrestrial life first bloomed, were as high as 35 percent (as opposed to nearer 20 percent now). This allowed animals to grow remarkably large remarkably quickly.
对于那些学会了从空气中呼吸氧气的动物来说，日子是不错的。在陆地生命大幅度增加的泥盆纪和石炭纪，空气中的氧的浓度高达35%（现在是将近20%）。因此，动物能以惊人的速度长到惊人的个儿。