While in our own day the names of certain English and German scientists (Darwin, Spencer, Huxley, Tyndall, Romanes, Buechner, Vogt, Haeckel) are inseparably connected with a history of this hypothesis, its roots are found far back in the early ages of Greek philosophy. A theory of evolutionary development was first propounded by Greek thinkers living about 600 years B. C. The human mind is ever on the search for unifying principles, principles which account for entire groups of natural phenomena, and not for isolated phenomena only. The Greek mind sought a principle by which to account for the manifold and diverse forms of life in nature. Whence do all things come? How have they come to be what they are? Questions about the nature of the universe in which we live have been asked from the very beginning. The moment the human mind began to reflect the notion that the vegetation which covers the earth, the animals which inhabit it, the rocks and hills, the mountains and valleys which constitute its physical features, may have undergone changes in past time, and that all the phenomena which constitute the animal, vegetable and mineral worlds as they now exist, are but modifications of other forms which have had their day and their philosophy, the idea of development became prominent. The early Greek philosophers were the first to attempt answers to these problems. Many of them held that all things natural sprang from what they called the original elements--fire, air, earth, water. Anaximander held that animals were begotten from the earth by means of heat and moisture; and that man was developed from other beings different in form. Empedocles had a fantastic theory, viz., that the various parts of man and animals at first existed independently, and that these--for instance, arms, legs, feet, eyes, etc., gradually combined--perhaps after the manner in which automobiles are assembled; and that these combinations became capable of existing and even of propagating and reproducing themselves. Anaxagoras was of opinion that animals and plants sprang from the earth by means of germs carried in the atmosphere which gave fecundity to the earth. Aristotle held opinions not very unlike those of our own day. All of which goes to show that speculation about the origin of the universe and the why and wherefore of living things did not come into existence with the Darwinian hypothesis and that the doctrine of descent with modification as an explanation of all biological phenomena antedates by over two thousand years the publication of the "Origin of Species."