几乎在每个人的一生中都会有这么一刻,一个人会突然惊恐地意识到,她是多么可能根本不会来到这个世界上:她的父母多么可能错失机缘,或者某些其他关键性的家族事件多么可能根本不会发生。进化生物学家们以同样的方式思考过他们最为棘手的问题之一:如果时光倒流,进化史重演,眼前的生物世界有多少是偶然的存在,又有多少可能没有进化呢?一些科学家已开始寻找巧妙的方法来测试进化的可重复性。他们逐渐发现,他们过 Almost in every person’s life there will be a moment when one suddenly realizes with horror how much she may not come to this world at all: how her parents might miss the chance, or some other crucial family How much of an incident may not happen at all. Evolutionary biologists have thought about one of their thorniest issues in the same way: If time flies back and evolutionary history repeats, how much of the immediate biological world is accidental, and how many may have not evolved? Some scientists have begun Find clever ways to test the repeatability of evolution. They gradually discovered that they had