Abstract
Evolution as a plausible explanation for the origin of all living organisms has received serious consideration for at least two centuries. During this period there has been an intensive search for a mechanism that could create the complex from the simple. Changes in nature usually tend towards randomness and not towards making special structures and systems as needed for evolutionary advancement. This process of increasing complexity in design mandates some kind of unusual mechanism. Evolutionists have proposed many. A brief review of the dominant ideas is instructive.

1. Lamarckism

At the beginning of the 19th century the French biologist Lamarck advanced what is usually considered to be the first serious proposal for an evolutionary mechanism. He suggested that use of an organ would cause it to improve, and this improvement would be passed on to the next generation. Thus, a deer-like animal could eventually evolve into a giraffe by persistent stretching of the neck. His ideas are not given serious credence at present, except for a few special cases.

2. Darwinism

About half a century later, Charles Darwin and Alfred Russel Wallace in England suggested that evolution advanced by a combination of variation and survival of the fittest. Continual natural selection of the fittest produced advanced forms. Darwin stressed the importance of small changes. He put forward a new mechanism for the inheritance of newly acquired characteristics. His model of reproductive cells contained "gemmules" which came from all over the body and passed on the new characteristics to the next generation. Darwin's idea of survival of the fittest, while severely challenged, is still given serious consideration. His idea of gemmules is not.

3. Mutations

Prominent among the detractors of Darwin was Hugo de Vries in Holland who, around the turn of the century, suggested larger evolutionary changes called mutations. He considered these to be the significant evolutionary process, in contrast to Darwin's smaller changes. While the interpretation of his experiments turned out to be largely erroneous, real mutations were discovered later by F. H. Morgan. Unfortunately for the evolutionary viewpoint, these changes turned out to be overwhelmingly detrimental. Some evolutionists still stake their hopes on the potential of a few beneficial mutations.

4. Population Evolution

Early this century, R. A. Fisher in England and Sewall Wright in the United States developed sophisticated mathematical models of evolution that helped shift the emphasis of an evolutionary mechanism from individual organisms to populations. Fisher emphasized small changes in large populations. Wright wanted smaller populations to facilitate the manifestations of new mutations, but not so small as to engender the deleterious effects of inbreeding. The question of proper population sizes for progressive evolution is still debated.

5. Modern Synthesis

The modern synthesis is a vague combination of the mutation concept and Darwin's idea of survival of the fittest. It has been championed by many leading evolutionists during the middle of this century, including Julian Huxley, the grandson of Darwin's promoter Thomas Huxley. The modern synthesis did not remain long as a synthesis, although it still has many adherents. Numerous problems developed, including questions about population sizes and especially how random mutational changes could produce the large changes necessary for new organs and systems. These changes seemed to require a very complex correlation of mutations or some kind of survival value through awkward intermediate stages. For instance, in the evolution of the forelimb of a reptile into the wing of a bird - assuming birds evolved from reptiles -, one must postulate either all kinds of correlated changes occurring simultaneously to produce a wing, or intermediates which were neither good limbs nor good wings but would be able to survive. Both postulates seem quite unworkable.

6. Diversity Period

After the modern synthesis, the plot for evolution has thickened considerably due to new information and a number of disputes that persist to the present. The current status of evolutionary mechanisms can best be characterized as both diversified and controversial.