The theory of evolution is the basis for understanding life on earth. An important part of the theory is the first point. The idea of Perpetual Change is followed by other concepts; those of common descent of all species, multiplication of all species, gradualism and, lastly, natural selection.
All of these five things support the theory of evolution, but they also stand alone as individual theories, supported by differing bodies of evidence.
The theory of Perpetual Change is exactly as it sounds. Today, scientists routinely use fast microbial evolution to track disease theory and note differing adaptations, but in Charles Darwin’s time, he had direct evidence all around him that many species for the most part were related, and had only changed over vast periods of time.
That they changed minutely, and very slowly, was observable in the fossil record. More overtly, in artificial selection, as was practiced in Darwin’s day with cattle stock, pigeons and dog breeds, Darwin knew that introducing a new trait resulted in an observable hereditary alteration. People were indeed selecting favorable traits by manipulating nature, and the reality of evolution was apparent, even when no one knew quite what the implications actually are.
The theory of Perpetual Change was particularly supported by fossil records which were accumulating huge stockpiles of data and specimens in Darwin’s day. Fossil hunting was somewhat of a fad in Victorian times. But science was amazed and baffled by the astounding amount of variation of form, adaptation of size, probable diet, and the mysterious total disappearance of so many organisms after many epochs passed.
From the warm and balmy days of the Jurassic to the frozen Pleistocene, fossil hunters were assured many different animals lived at different times. Perpetual and dynamic change over time was Darwin’s brilliant insight. He chose to call the agent for that change natural selection. The environment naturally selects, over eons, those traits that result from perpetual change.
By studying the subtle changes to be found even in modern day species, such as the finches he collected on his Galapagos travels, Darwin realized that changes could be very subtle, but meaningful, in the success and ultimate passing on of genetic traits.
All of this was deduced before the discovery of DNA, or the double helix blueprint that all organisms on earth share.
For noting all living things begin with one very basic pattern that then becomes so varied and widespread that individual species are formed, Darwin’s first recognition of perpetual change was the first idea from which a wellspring of understanding all life was to flow forth. It is the first critical insight Charles Darwin had, one that changed the world.