如果他们找到了一颗裂开的、风化的牙齿,凭着这块仅有的来自数百万年前的哺乳动物的一部分,他们就能宣布那是一只虎,一只懒猴,一只有袋动物,还是一个原始人类。从一开始,鲸的牙齿就已经在帮助古生物学家发现它们真实的历史。生物是其进化历史的产物,在它们互有关联的历史上由于受到胚胎成长方式的约束,它们之间可能保持着一定的一致。有些化石中的生物似乎与现存的生物没有任何关联,而另 If they find a cracked, weathered tooth, with the only part of the mammal that came from millions of years ago, they can declare it a tiger, a sloth monkey, and one Bag of animals, or a primitive human. From the very beginning, whale’s teeth are already helping paleontologists find out their true history. Creatures are the product of their evolutionary history, and there may be some agreement between them in the history of their interrelatedness that is constrained by the way in which embryos grow. Some creatures in fossils do not seem to have anything to do with existing creatures, and the other