Darwin was the naturalist aboard the HMS Beagle for a trip to the Galapagos islands of the South American coast in the Pacific ocean. The basic elements of his logical argument for evolution was as follows:
- He saw large populations of birds and other species.
- He noticed there were limited resources of food and shelter.
- There would be a struggle for existence within a given species.
- He saw a variation among individuals within a species.
- For example, finches beaks varied long, short, thin, stout, straight and curved.
- He noticed that some of these variations were heritable from parent to offspring.
- Some of these variations were beneficial; others were detrimental. Long, curved beaks were well suited to get insects out of holes in the rocks. Short, stout beaks were better suited for defense against a predator.
- As such there would be a differential in the reproductive success between them depending upon the surroundings.
- The fittest will be more likely to have offspring.
- Populations will evolve over time.
There is really nothing wrong with Darwin's logic based on his observations. But notice what he did not observe: that there were limits to which variations can occur. The reason he did not notice it was because he was not looking for it.
How do we know there are limits? Darwin was noticing what he called "natural selection" which works very slowly and consequently it is impossible to see the limitations since one would have to wait many thousands of generations to see it. But what about unnatural selection? I am talking about "intelligent breeding." This is where a farmer breeds his corn crops for the largest, sweetest and most yellow corn. Or where a rancher breeds for the largest steer or fattest cows or the meatiest hog. Because they use intelligent breeding, they speed up the process of genetic variation by many times. What these farmers and ranchers know through experience is that you can only get an ear of corn so big and so sweet and so juicy before you reach a limit. And they never see corn becoming something other than corn. Furthermore, they notice that as you continue to selectively breed, weaknesses sometimes result. The corn may be sweeter, but it becomes more susceptible to insects.
Another limitation is when trying to cross breed species, different kinds of animals and plants are not able to breed with each other to produce offspring. Dogs and cats cannot have offspring. Interestingly you can breed a horse and a donkey to get a mule but what is the problem with the mule? Mules are infertile.
If Darwin had combined his observations with the practical knowledge of the rest of the world, he might not have been as far-reaching in his ideas about evolution. The migration of a population progressing from one kind to another kind was all imagination and not observation. What he did observe is explained by the well-known ability of the gene pool of dogs for example to produce a fantastic variety of poodles to Great Danes, all dogs mind you. But Darwin was driven by a desire to find an explanation apart from what God had said:
Genesis 1:24 (NKJV)
Then God said, “Let the earth bring forth the living creature according to its kind: cattle and creeping thing and beast of the earth, each according to its kind”; and it was so.