Although Charles Darwin was not the first person to consider that life on this planet evolved, it is important to keep in mind that he was the first to come up with a viable working mechanism on how it happened.

Around 520 BC - Anaximander
The Greek philosopher, Anaximander of Miletus, wrote a text called "On Nature" in which he introduced an idea of evolution, stating that life started as slime in the oceans and eventually moved to drier places. He also brought up the idea that species evolved over time.

Around 500 BC - Xenophanes
Xenophanes studied fossils and put forth various theories on the evolution of life.

Around 350 BC - Aristotle
The Greek philosopher, Aristotle, studied marine animals and developed an epigenetic model of evolution. He also developed a classification system for all animals.

1686 - John Ray
John Ray's book, "Historia Plantarum" catalogued and described 18,600 kinds of plants and gave the first definition of species based upon common descent.

1735 - Carolus Linnaeus
Carolus Linnaeus, a Swedish born naturalist, published his book, "Systema Naturae" in which he outlined a method for classifying all organisms. This method is still in use today (generas, orders, classes and kingdoms). His views on evolution were rather tame. He believed that new species within genera came into being through hybridization, but only under the controlling hand of god. He also thought there was a divine order to all organisms and developed his classification system to reveal this order.

1749 - Comte de Buffon
Comte de Buffon, a French naturalist, developed the modern definition of a species; a group of organisms which can breed and produce fertile offspring. He thought that all organisms were created by god and arranged in a hierarchy with mankind at the top of creation. Buffon did believe in evolution, but thought that the environment was the direct agent of change, rather than competition between species. He did not describe the mechanism by which this takes place, however.

1751 - Pierre-Louis Moreau de Maupertuis
Pierre-Louis Moreau de Maupertuis in his book, "Systeme de la Nature" theorized on the nature of heredity and how new species come into being. He thought that speciation took place by chance events in nature, rather than by spontaneous generation as was believed at the time. About ten years earlier he had published a book called, "Essai de Cosmologie" in which he introduced the concept of stronger animals in a population having more offspring, something akin to Darwin's theory of the survival of the fittest.

1770 - Charles Bonnet
Charles Bonnet, a Swiss naturalist, wrote in his book, "Philosophical Palingesis" that the females of each organism contain the next generation in miniature form. He believed that natural catastrophes sparked evolutionary changes in organisms. His idea of evolution was analogous to organisms climbing a ladder of life, with animals becoming intelligent, primates becoming human, and humans becoming angels.

1790's to 1830's - Georges Cuvier
Georges Cuvier, a French naturalist, made numerous contributions to the biological sciences. He was the founder of vertebrate paleontology, confirmed that species can become extinct, and developed a classification system for animals that is still in use today (vertebrates, articulates, molluscs and radiates). Cuvier believed that animals were functional wholes. In other words, if any part of an animal were to become modified the animal would die because all of its parts are interdependent. It follows from this that Cuvier did not believe in evolution of any kind. He also believed that an animal's function determined its form.

1794 - Erasmus Darwin
Erasmus Darwin, English physician, poet and naturalist, developed one of the first theories of evolution in his book, "Zoonomia." Erasmus thought that all life had evolved from one common ancestor which over time branched off into all the species we see today. He thought the transmutation of species was driven by competition and sexual selection, but he had no facts to support his theories. Erasmus Darwin was Charles Darwin's grandfather.

1809 - Jean-Baptiste Lamarck
Jean-Baptiste Lamarck's book, "Philosophie Zoologique" stated that animals evolved from simpler forms. Lamarck saw evolution as a goal oriented process striving towards perfection; analogous to species climbing a ladder. One result of this view was that he did not believe species became extinct, rather, they simply evolved into a different species. For Lamarck the process of evolution was a simple one - as the environment changes species need to modify how they interact with it in order to survive. As a species used a particular structures more often that structure grew bigger (or smaller if used less). Lamarck also supported the notion of inherited characteristics; any changes that occur through use or disuse are passed on to the next generation. Lamarck coined the term "invertebrates" and in 1802 he (with Trevirons) coined the term "Biology" for the first time.

February 12, 1809 - Charles Darwin
Charles Robert Darwin was born in Shrewsbury, England.