Evolutionary History

Historically, it was assumed that species were comprised of fixed organisms for as long as they were extant. This viewpoint extends as far back as Greek philosophy. One example philosopher was Aristotle (circa 300 B.C.E.), who developed the “Great Chain of Being”. This perspective of permanent perfection persisted into the development and rise of Western Christianity (seen in the Old Testament and the Genesis.) At the time, it was propagated by Bishop James Usher (circa 1694), who developed a “Date of Creation” based on Biblical literature.

However, scientific advancements in the Middle Ages and the Renaissance disputed early philosophical and religious claims. The scientific theory and the use of verifiable, replicable observations and tests ushered a new understanding of the world and the universe. Early important scientists include Nicolas Copernicus, who identified heliocentrism, and Sir Isaac Newton, who identified the theory of gravity. They were followed by geologists such as James Hutton (circa 1795), who proposed the principle of gradualism, and his colleague Charles Lyell (circa 1830’s), who proposed the theory of uniformitarianism. Hutton and Lyell’s work paved the way for a new worldview of the Earth and the biology upon it—most importantly the theories of evolution and natural selection.

Both the principle of gradualism and the theory of uniformitarianism were widely accepted by the mid-1800s. They rose in prominence alongside the discovery of fossil evidence of extinct organisms. However, they were not accompanied by a proposed mechanism for the changes in characteristics. At the time, no complete explanation was given for the variation in traits, with an emphasis in those related to an organism’s body type (an example of a phenotypical change).

The first and primary hypothesis proposed before the backbone proposal of modern evolutionary theory was suggested by Jean Baptiste Lamarck circa 1809. He proposed the concept of “acquired characteristics” and the “Inheritance of Acquired Characteristics” hypothesis based on a “use or disuse” principle. This hypothesis would be invalidated following evolutionary and genetic evidence after the first half of the 1800s onwards as well as the proposal of evolution by natural selection. Charles Darwin and Alfred Russel Wallace jointly presented their findings on natural selection, discrediting religious and philosophical schools of thought as well as Lamarck’s proposed mechanism. Following this presentation, the former published, On the Origin of Species, his manuscript on natural selection, leading to his fame and credit as the “father” of Modern Evolutionary Theory as the theory dominated scientific spheres.

emergence of modern evolutionary theory and natural selection