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 βGreat Chain of Beingβ. 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 βDate of Creationβ 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 1830βs), who proposed the theory of uniformitarianism. Hutton and Lyellβs work paved the way for a new worldview of the Earth and the biology upon itβmost 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 organismβs 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 βacquired characteristicsβ and the βInheritance of Acquired Characteristicsβ hypothesis based on a βuse or disuseβ 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 Lamarckβs 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 βfatherβ of Modern Evolutionary Theory as the theory dominated scientific spheres.
emergence of modern evolutionary theory and natural selection
- charles darwin: βfatherβ of modern evolutionary theory; lived in england, dominated by western christianity conventionalism (church of england)
- hms beagle 1832-1836 naturalist, galapagos (oceanic)
- manuscript received from alfred russel wallace; scientific paper by arw about indonesian /sea observations
- joint presentation of identical conclusions + publication of darwinβs manuscript
- separate systems evidence
- speciation from ancestors, nodes, taxa; no fixed species
- changes occur when a mutation/variation in a population is reproduced
- merit of βsuccessβ by genetic reproduction; beneficial versions are typical
- heritable traits and incremental frequency (gradualism/uni)