losopher Anaximander thought that a gradual evolution had created the world's organic coherence from a formless condition, and he had a fairly modern view of the transformation of aquatic species into terrestrial ones. Following the rise of Christianity, Westerners generally accepted the explanation provided in Genesis, the first book of the Judeo-Christian-Muslim Bible, that God created everything in its present form over the course of six days. However, other explanations existed even then. Among Christian theologians, for example, Saint Thomas Aquinas (1225 to 1274) stated that the earth had received the power to produce organisms and criticized the idea that species had originated in accordance with the timetables in Genesis.1 --------------------------------------------------------------------------------Charles Darwin (1809-1882) Charles Darwin, Alfred Russel Wallace, and Gregor Mendel laid the foundations of modern evolutionary theory. During the early 1800s, many naturalists speculated about changes in organisms, especially as geological investigations revealed the rich story laid out in the fossilized remains of extinct creatures. But although ideas about evolution were proposed, they never gained wide acceptance because no one was able to propose a plausible mechanism for how the form of an organism might change from one generation to another. Then, in 1858, two English naturalists—Charles Darwin and Alfred Russel Wallace—simultaneously issued papers proposing such a mechanism. Both men observed that the individual members of a particular species are not identical but can differ in many ways. For example, some will be able to run a little faster, have a different color, or respond to the same circumstance in different ways. (Humans— including any class of high school students—have many such differences.) Both men further observed that many of these differences are inherited and can be passed on to off...
