The widely believed belief that all life is connected and descended from a common ancestor is Darwin's Theory of Evolution: birds and bananas, fish and flowers are all related. Darwin's general theory assumes the emergence of life from non-life and emphasizes a "descent with modification" that is completely naturalistic (undirected). That is, sophisticated species organically evolve from simpler forebears over time. In a nutshell, as random genetic mutations arise within an organism's genetic code, the favorable changes are maintained because they assist survival — a process known as "natural selection" — and passed down to the next generation. Beneficial mutations accumulate throughout time, resulting in a whole new organism (not just a variation of the original, but an entirely different creature). While Darwin's Theory of Evolution is a recent concept, the evolutionary mindset is as old as time. Anaximander and other ancient Greek philosophers proposed the evolution of life from non-life and the descent of man from animal. Charles Darwin simply added a convincing mechanism termed "natural selection" to the previous concept. Natural selection acts to maintain and accumulate tiny favorable genetic variations. Assume a species member has obtained a functional advantage (it grew wings and learned to fly). Its descendants would inherit this benefit and pass it forward to their descendants. Darwin's Theory of Evolution is a slow gradual process.
Who is Charles Darwin?