Evolutionist, believe that all life arose from one common ancestor. They believe that the universe has always existed and didn't come into existed by supernatural forces such as God. Evolutionists also predict that the earth is billions of years old. In Darwinian terms, evolution refers to changes accumulated by natural selection in living, especially regarding species formation (Zetterburg 30; McGowan 21-22). The action of natural selection, operating over a long period of time, would cause a species to become better adapted to its environment and hence change. Darwin believed that the environment was slowly changing and as a species modified to this change it eventually became a new species-the alternative was extinction. Some of these variations increase an individual's chance of survival and hence leave more offspring. Since their offspring inherit their parents" features, they too have an increased chance of survival. Many people learned in elementary school that a theory falls in the middle of a hierarchy of certainty--above a mere hypothesis but below a law. However, all sciences frequently rely on indirect evidence. Physicists cannot see subatomic particles directly, for instance, so they verify their existence by watching for telltale tracks that the particles leave in cloud chambers. The absence of direct observation does not make physicists' conclusions less certain. Creationists retort that a closed-minded scientific community rejects their evidence. Yet, few antievolution manuscripts are even submitted. Some antievolution authors have published papers in serious journals. Those papers, however, rarely attack evolution directly or advance creationist arguments; at best, they identify certain evolutionary problems as unsolved and difficult (which no one disputes). In short, creationists are not giving the scientific world good reason to take them seriously (Rennie 57).