One misconception that often appears in the writings of physical scientists who are looking at biology from the outside is that the environment appears to them to be a static entity, which cannot contribute new bits of information as evolution progresses. This, however, is by no means the case. Far from being static, the environment is constantly changing and offering new ① challenges to evolving populations. For higher organisms, the most significant changes in the environment are those produced by the contemporaneous evolution of other organisms. The evolution of a horse’s hoof from a five-toed foot has ② enabled the horse to gallop rapidly over open plains. But such galloping is of no ③ advantage to a horse unless it is being chased by a predator. The horse’s efficient mechanism for running would never have evolved except for the fact that meat-eating predators were at the same time evolving more efficient methods of ④ attack. Consequently, laws based upon ecological relationships among different kinds of organisms are ⑤ optional for understanding evolution and the diversity of life to which it has given rise.

* hoof: 발굽 ** gallop: 질주하다 *** predator: 포식자