A long path leads from the origins of primitivelife,? which existed at least 3.5 billion years ago, to the profusion and diversity of life that exists today. This path is best understood as a product of evolution. Contrary to popular opinion, neither the term nor the idea of biological evolution began with Charles Darwin and his foremost work, On the Origin of Species by Means of Natural Selection (1859). Many scholars from the ancient Greek philosophers on had inferred that similar species were descended from a common ancestor. The wordevolution? first appeared in the English language in 1647 in a non-biological connection, and it became widely used in English for all sorts of progressions from simpler beginnings. Some common errors about the theory of evolution are illustrated by such questions asIf man evolved from the apes, then why are there still apes?? The theory of evolution is not equivalent to Darwinism. The term Darwin most often used to refer to biological evolution wasdescent with modification,? which remains a good brief definition of the process today. The extensive evidence in support of both fact and theory of evolution is an interrelated set of now well confirmed hypotheses including descent with modification, natural selection, and genetics as being the mechanisms behind the evolutionary process itself.
The descent with modification component of evolutionary theory is that all life forms can trace their lineages back to earlier classes of life forms in a branching,nested? hierarchy (forming what looks like a bush or tree, as in theTree of Life?), which can ultimately be traced back to the beginning of life on earth (a point that would likely have been the culmination of a long period during which the distinction between living and non-living matter would have been difficult to make). During the long period since that time, changes in body plans have accumulated in diverse directions to make all the differences we now see between all life forms.