Darwin’s theory of evolution starts with the concept of variation existing among different organisms within a group. Darwin differentiated between three approaches to variation:
- There is inheritable variation in each species (including domesticated species);
- Some of the inheritable variations are more productive for obtaining resources, surviving, and producing offspring;
- There is always a struggle for scarce resources among variations.
Thus, it might be noted that the more useful variations were more inheritable. Further, such variations had more chances for reproduction and, as a result, they increased in frequency. Such an explanation was given for the evolution by natural selection. However, there was also a concept which Darwin called “chance” or “accidental” variation. This issue played a prominent role in the theory of evolution by natural selection. According to Mivart, in order for evolution by natural selection to provoke the acquisition of a new feature, each step along the way would have to be useful for organisms. Hence, there was a problem of the usefulness of the so-called “incipient” stages.
Scholars note that when Darwin spoke of “chance” variation, he meant several different things. The first issue was that variation was not understood as the adaptive response to the environment. As a result, it was assumed that variation was created by the environment. However, the environment did not always cause adaptive variations. The second view concerned Darwin’s belief that the complexity of relations between variation and the environment led to unpredictability.
Thus, Darwin divided variations into predictable and unpredictable, and he considered the majority of them to be unpredictable. The third type of “chance” variation was associated by Darwin with formally interpreted probability. He considered that there was more probability of the “accidental” variation in a large population and over a long time than in a small population within a short period.
Darwin’s notion of the “chance” variation might be compared with Baptiste’s laws of zoological philosophy:
- In any animal which has not “passed the limit of its development,” the organ that is constantly used will strengthen gradually. The power of such an organ will be proportional to the time period over which it has been used. On the contrary, if an organ has been not used for some time, it will weaken and will eventually lose its functional capacity;
- All the losses or acquisitions of individuals are created by nature with the help of the environment’s effect. Thus, the predominant use or disuse of some organ is preserved for the future generations.
The mentioned laws can be related to the “chance” variation in that it also occurs at some point to some features. However, further, there is no similarity between the laws and variations. Unlike laws, variations occur inconsistently, and they are not necessarily passed to the next generations. The role of variations in Darwin’s theory of evolution was twofold: for one thing, it was connected with the contingency of evolution’s outcomes; for another, the meant chance divergence. Natural selection’s effect on different variations led to divergent results. The outcome depended on when and what kind of variation took place.
Darwin’s idea of the natural selection of chance variations raised some controversy concerning theological dimensions. Darwin’s reviewers were convinced that the scientist’s hypothesis of species origination through natural selection and variation rejected “all indication or purpose in the organic world”. While Gray did not entirely agree with such an opinion, the author remarked that Darwin’s silence “upon the philosophical and theological applications of his theory” was purposeful. Gray further mentioned that Darwin was more accustomed to working with natural-historical inquiries than with philosophical ones. However, Gray remarked that because natural science dealt only with natural causes, there should not have been made a distinction between the scientific terms of the theory of species derivation to theists and atheists. The difference occurred when the question referred to the primary cause: in that case, it belonged to the realm of philosophy. Therefore, as Gray noted, Darwin’s unwillingness to touch upon philosophical dimensions should not disturb the public.
Still, Gray considered that Darwin’s book was written in accordance with the theistic view of nature. Such an opinion might be supported by excerpts from Darwin’s notebook, where the scientist dwelled upon theological dimensions of evolution. For instance, when describing the nature at Galapagos, Darwin remarked that he believed that “the Creator created by… laws,” which could be noticed by “the very facts of the Zoological calendar” of the island. Darwin also mentioned that “God orders each animal created with certain form in certain country”. Further, the scientist noted that the fact that some species died and other replaced them was also related to theology. Also, when analyzing Le Comte’s idea of the theological state of science, Darwin remarked that it was “grand” on condition that everything in nature “would be placed to the will of God”.
Therefore, it might be concluded that although Darwin’s theory of evolution was based on variation, he also paid sufficient attention to the explanation and analysis of “chance” or “accidental” variations. The scientist admitted that some species did not evolve in the same way all the time, which led to numerous inconsistent changes in their development. However, “chance” variations had fewer opportunities to reproduce and, therefore, they did not increase in number considerably. It was also noted that all stages of evolution by natural selection were important for the provocation of new features’ acquisition. Darwin meant three things under “accidental” variation: variation was not the adaptive reaction to the environment, the links between variation and environment were not always predictable, and variation was related to probability.
Another important conclusion concerning Darwin’s understanding of “chance” variations” is that the scientist associated his theory with theology even though his reviewers did not consider it so. In fact, he expressed some thoughts about God and his power in regard to Darwin’s fundamental work. Darwin admitted that there were some processes in biology and evolution that could be explained through the higher power and even made some assumptions in his personal notebooks. Therefore, “chance” variation played an important role in Darwin’s theory of evolution by natural selection.
