Living cells contain thousands of different chemicals, some acidic, others basic. Many chemicals would react with others unless an intricate system of chemical barriers and buffers already existed. If living things evolved, these barriers and buffers must also have evolved—but at just the right time to prevent harmful chemical reactions. How could such precise, seemingly coordinated, virtually miraculous events have happened for each of millions of species? a
All living organisms are maintained by thousands of chemical pathways, each involving a long series of complex chemical reactions. For example, the clotting of blood, which involves 20–30 steps, is absolutely vital to healing a wound. However, clotting could be fatal if it happened inside the body. Omitting one of the many steps, inserting an unwanted step, or altering the timing of a step would probably cause death. If one thing goes wrong, all the marvelous steps that worked flawlessly up to that point would have been in vain. Evidently, these complex pathways were created as an intricate, highly integrated system.b