I read a Christian magazine recently that complained about Charles Darwin's theory of evolution. More specifically, it complained that his book, Origin of Species, was more of a theological dissertation than a scientific treatise.
It's not true. The person who wrote that complaint did not understand what led Darwin to the idea of "natural selection." The writer did not understand what problem the Darwin's theory of evolution was meant to solve.
Darwin's job, as a naturalist, was to classify each species by whether or not it was created individually by God.
It took only a little time for him to find out that such decisions were impossible to make with any degree of certainty.
Charles Darwin's theory of evolution, which he called "natural selection" or "descent with modification," was an attempt to explain how species came about. Thus it was titled On the Origin of Species by Natural Selection. There was a reason for that name. The reason has everything to do with why Origin of Species contains theological statements.
Charles Darwin was a naturalist. That means that he studied nature. Today, he might be called a taxonomist. He studied and classified living organisms.
In Darwin's day almost everyone believed that each species was separately created. Darwin writes:
The problem with this is that some creatures that clearly seemed to be separate creations were known not to be.
One specific example mentioned by Darwin was domesticated pigeons. These varied so greatly in size and form that they seemed to be not only multiple species, but also multiple genera [genera is plural of genus, see sidebar].
However, everyone knew all domesticated pigeons descended from Rock Pigeons. Thus, no matter how different they were and whether or not they could interbreed, they all had to be one species.
Darwin, in his role as a naturalist, had to determine which types of plants and animals were separately created and which were descended from a common ancestor (like the various breeds of dogs).
Only those who have done that can know how difficult it is. Creationists like to say that life falls neatly into categories, but it does not. Which cats have a common descendant, and which were separately created? Which rodents? Which oak trees?
What about geese and ducks? Could they be related?
Are they more different than St. Bernards and dachshunds?
Darwin's theory of evolution is the product of addressing exactly such question.
In other words, when a naturalist is young and relatively ignorant, he knows few forms and considers most of them to be separate species. However, as he becomes more experienced and encounters more forms, the gaps begin to fill in, and it becomes difficult to determine what is a species and what a mere variation.
In other words, intermediate forms—or missing links, as we are prone to calling them—are not only found in the fossil record, but in living species as well!
Darwin began to see a progression in living creatures. This is exactly, according to Darwin himself, what led to the his theory of evolution (or "descent with modification," as he called it) ...
I would love to use Darwin's own words to explain what he was seeing, but since they are 150 years old it is better to paraphrase in my own words. This, updated somewhat in grammar and wording, is the explanation Darwin himself gave in Origin of Species for how he saw this progression:
In other words, it was clear from the tight progression in living organisms that each variety was slowly developing into a new species.
Not all of them make it, of course. Some varieties die out, never making it to become classed as their own species, or they interbreed again with the parent stock. Many, though, continue to develop, becoming further and further from their parents, leaving a long line of barely recognizable distinctions in their wake.
This was the origin and content of Charles Darwin's Theory of Evolution.
As varieties and species go extinct, gaps are made in the living organisms found on earth. Thus in some cases we can find the whole progression of varieties still alive and thriving, making it difficult to classify some forms of life. In other cases, however, where a variety or whole series of varieties have gone extinct, gaps are created, allowing us to easily distinguish specific species.
This was the speculation of the Charles Darwin theory of evolution.
Darwin was aware when he wrote those words in chapter 2 of Origin of Species that they were mere speculation; speculation based on much research and thought as a naturalist, but speculation nonetheless.
Darwin, like all scientists, did not leave the Charles Darwin Theory of Evolution as mere speculation. He researched; he asked questions; he experimented; he consulted other scientists. In other words he tested his speculations, which are known in science not as speculations but as hypotheses.
The scientific method encourages speculation, but it never leaves a hypothesis as speculation. It subjects hypotheses to the most rigorous examination and testing possible. In this way, truth—good, practical, useful truth that heals diseases and sends spaceships to Jupiter's moons—is determined.
It is the rest of this site that looks at the rigorous examination and testing to which Darwin's speculation, his theory of evolution, has been put. That cannot be done on one page. But I invite you to explore ...