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It is sometimes claimed by those who wish to denigrate the achievements of Charles Darwin that he was little more than a "serial plagiarist". He is supposed to have lifted his central ideas, without giving due credit, from a number of precursors including earlier evolutionists and formulators of the principle of natural selection. This essay aims to show that Darwin, like any scientist, had influences, but that he was honest in his theoretical development. Since the material and secondary comment is scattered I thought it would be useful to have an introduction giving the references.

Mere use the word "evolution" is no indication that an author's theory of origins is the same as Darwin's, either before The Origin or after¹. A good many of those who preceded Darwin believed that species were mutable - that is, they were not static and unchanging kinds - and many if not most of those biologists and geologists who followed him had a view of evolution that was based not on his own views, but on those of his precursors, up to the period of the "modern" synthesis of the 1930s and 1940s. The very word "evolution" originally meant "to unfold" and referred to the development of the fetus, until Lamarck used the analogy, still strong until this century, between the growth of a single organism and the development of a species. Darwin didn't use the term until long after he had formulated his theories, preferring instead to use terms like "transmutation".

Darwin's views changed a bit themselves in the post-Origin era, as well. However, from about 1844 we can see a robust and stable set of theories that we can call "Darwinian"². They are:

Sidenote: This differs from the list of five theories that Mayr outlined for Darwin's theory3, where he lists "Evolution as such" (= Transmutationism) Common Descent Gradualness Populational speciation, and Natural Selection. I think that gradualness is a feature of the then dominant Uniformitarian views of Lyell, and that populational speciation is not a theory proper so much as a new way of dealing with biological data. On the other hand, sexual selection, the struggle for existence and biogeographic distribution are positive hypotheses, while Darwin's views on heredity are focal to many confusions of his theory, even though he did not publish them until well after the Origin.

1. Transmutationism (also called by Darwin "Descent with Modification"). This word means in context that species change ("mutate", from the Latin) from one species to another. It is in opposition to the prevailing Aristotelian views that species were natural kinds that were eternal.

2. Common descent. This is the view (not held by all evolutionists prior to Darwin or even after) that similar species with similar structures (homologies) were similar because they were descended from a common ancestor. Darwin tended to present the cases for limited common descent - i.e., of mammals or birds - but extended the argument to the view that all life arises from a common ancestor or small set of common ancestors.

3. Struggle for existence. This is the view that more organisms are born than can survive. Consequently, most of those zygotes that are fertilised will die, and of those that reach partition (birth) many will either die or not be able to reproduce. The competition here is against the environment, which includes other species (predators and organisms that use the same food and other resources). This is interspecific (between species) competition.

4. Natural selection. This is a complex view that species naturally have a spread of variations, and that variants that confer an advantage on the bearer organisms, and are hereditable, will reproduce more frequently than competitors, and change the "shape" of the species overall. Notice here that this competition is mostly intraspecific, i.e., between families of the same species (and indeed of the same population).

5. Sexual selection. Many features of organisms are obvious hindrances (such as the tails of birds of paradise), and these often occur in one sex only. Darwin argued that there was competition for mating opportunities and any feature that initially marked a gender out as a good mating opportunity would become exaggerated by the mating choices of the opposite gender. Competition here is between conspecifics of the same gender.

6. Biogeographic distribution. Darwin and Wallace were concerned to explain why species were found in the areas they were, and argued that dispersal of similar, but related, species was due to their evolution in one place and migration into other regions.

7. Heredity. Darwin knew very little about what we would call the principles of genetics. He accepted the prevailing and old view that the use of features of the organism would change the way those features were inherited.

With this list in place, we can usefully ask what of these views Darwin owes to others, and whether he was (i) aware of the debt, and (ii) he acknowledged it.

² Mayr 1982, p410

³ Mayr 1982, pp 505-510

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