Evolution is the theory that living organisms in the world developed from primitive beginnings through natural processes that took millions of years. Several philosophers in the Pre-Socratic Era of ancient Greece promoted forms of evolution. Anaximander (611–547 B.C.), for example, held that people evolved from fish. He believed this so strongly that he encouraged people not to eat fish since they were our ancestors. Empedocles (490–430 B.C.), too, believed in a form of evolution when he declared that chance formed matter into isolated limbs. For example, there once were arms without shoulders, heads without necks, and eyes without eye sockets, etcetera. These parts eventually linked into organisms in which there were beings like human-headed oxen and ox-headed humans. Only the fittest of these beings survived.
The early nineteenth century Frenchman, Jean-Baptiste de Lamarck, became the first to offer a detailed explanation of evolution. However, the English naturalist, Charles Darwin, is most associated with the theory of evolution. His thoughts on evolution developed as a result of his five-year tour of the globe on the ship, the HMS Beagle. His two landmark works that launched the theory of evolution were The Origin of Species(1859) and The Descent of Man (1871). According to Darwin, organisms varied based on their ability to adapt to their environments. Organisms evolve gradually to help them adapt to their surroundings. The fittest of species adapt and survive while weaker organisms do not survive.
Evolution has had enormous philosophical and religious implications. While evolution does not necessarily rule out the existence of God, it does offer a view of origins that is purely naturalistic. Many atheists and secular humanists have been attracted to evolution since it explains reality apart from any divine being or God. Before Darwin’s view of evolution, the Western world generally accepted the Genesis account in the Bible concerning the creation of the world in six literal days.
Darwin’s theory challenged other traditional beliefs including the perspective that the world was only a few thousand years old. With Darwin’s theory, millions of years are necessary since the gradual changes in species occur over long periods of time.Darwin’s view also challenged the traditional belief that people were made in the image of God and thus were radically different and superior to all other beings in the world. With evolution people are just the next step up from animals in the evolutionary process.
Evolution is a widely accepted theory today but it is not held by all scholars. While acknowledging that micro-evolution takes place within species, some have argued that irreducibly complex aspects of certain species rule out the possibility of evolution as posited by Darwin.