Ever since I was a child I have been fascinated by the world around me. I find great pleasure in exploring and learning, especially in the area of biology. From the sound of a chickadee to the sight of a soaring vulture, from the smell of spring flowers to the colors of autumn leaves, I find the natural world incredibly awe-inspiring. This appreciation for living creatures inspired me to study agriculture and veterinary medicine, earning several degrees from a large state university.
So many different kinds
There are many similarities between human medicine and veterinary medicine, but there is one rather obvious difference. Medical doctors practice on humans; veterinarians practice on many different species of animals. So as I began my study of veterinary medicine, there was an astounding amount of information to learn, including the anatomy and physiology of a variety of creatures.
Our first year we were required to study anatomy on three different mammals: the dog, the horse, and the cow. As we began studying the dog, I found that the names used for bones and muscles were essentially the same as those used in humans. It was still challenging. I hadn’t realized that anatomists name more than just bones, but every bump, groove, and opening has a specific name. The shape of the bones differed from those in humans, but the similarities were enough that my basic knowledge of human anatomy gave me a good base on which to learn canine anatomy. Even the digestive system of the dog had many similarities to that of humans.
The next quarter we studied the horse. There were many similarities to the dog, but a fair amount of time was spent on the differences. For example, the equine foot is quite different than that of a human or a dog. Some things were completely different, like the navicular bone and the design of the hoof.1 As we moved to the digestive system, more differences became apparent. The basics were the same: mouth with teeth and tongue, esophagus, stomach, small intestine, and large intestine. However, there were specifics about the teeth, stomach, and intestines that were quite different. For example, the horse has some interesting features in the large intestine that allow for bacteria to break apart the tough cellulose in the grass consumed by the animal.
This pattern of basic similarity with specific interesting differences continued into the next quarter as we studied the cow. In the cow, it is the stomach that has some fascinating modifications to allow microbes to digest the grass consumed. There were other differences as well. I learned to view mammalian anatomy as basically variations on a theme, because once I had an understanding of the basics of any system of the body (the theme), it was not as difficult to learn the differences found in various species (the variations).
Living things...are designed with patterns of similarities and differences that allow us to learn things about the biological world.
Although I didn’t realize it at the time, the approach I just described for learning anatomy has been discussed for decades by learning theorists. For example, seeing patterns of similarity and difference is a basic cognitive process that helps us make connections and learn about the world around us. We often learn best as we are able to put facts in the context of what we already know. When we don’t, we are more likely to forget the facts or never realize their significance. I was able to learn new facts in the context of material I knew in my study of anatomy and it made a seemingly impossible task easier. There were other things I was taught in veterinary school where I didn’t have much context into which I could place the information I was learning. It was much more difficult to retain knowledge when this was the case. Fortunately, this information was often repeated in different classes from slightly different angles over my four years, so I was eventually able to learn much of it.
This brings out another important aspect of biology. Not only are living things beautiful and awe-inspiring, but they are designed with patterns of similarities and differences that allow us to learn things about the biological world.
Biological similarity: a problem or a blessing?
It is common for creation scientists to discuss with each other the various challenges we run into as we continue to develop the creation model. I have to admit that I was in shock when I came across the idea that biologic similarity was a problem. I thought in horror about what vet school would have been like had there not been significant underlying similarity between different kinds of animals. It was chilling to think how difficult medical research would be without broad-based similarity throughout the animal kingdom. For example, mice were once best known as pests responsible for the death of many humans by destruction of grains, resulting in starvation, and by spreading disease. However, for decades now laboratory mice have been widely used in animal research and have contributed immeasurably to our understanding of disease and disease treatment. These small animals have helped save countless human and animal lives because they have similarities to other mammals, and those similarities aid our learning.
Of course, once I got over my initial shock, I realized what my creation colleagues were discussing regarding the “problem of similarity.” Evolutionists have long claimed similarity as evidence for the common ancestry of all life. Certainly common ancestry could be one reason why creatures are similar; this is especially true of different species belonging to the same created kind. However, common ancestry is not the only possible explanation for similarity. Even evolutionists recognize this, because similarity that shows up where it is not expected is known as convergent evolution. In other words, they propose that the similarity showed up twice (or more), independently, by chance and natural processes.
Necessity of Similarity
Creationists have pointed out that similarity in design between different kinds of animals is a reasonable pattern given a common Designer. Engineers commonly reuse various design elements in completely separate creations. Also, throughout history there have been composers, artists, and architects creating music, art, and buildings that have very distinctive patterns. For example, after I became familiar with Antonio Vivaldi’s Four Seasons, I later easily identified him as the composer of a different violin concerto. Correspondingly, similarities among living creatures may be one way God has made it clear there is a single Designer.
Of course there may also be other more practical reasons for many of the similarities that God designed. From a biochemical perspective, there are probably a limited number of ways one can get a living creature. Although it is common for science-fiction writers to conceive of silicon-based life forms, it is questionable if such life is even possible. Further, since life on Earth is interdependent, a similar biochemical basis would seem necessary so creatures can digest and use available food sources.
Not surprisingly, creatures that are more similar in anatomy and physiology tend to be more similar genetically. We share some genes with bacteria and plants, we share more with fish and birds, but we share the most with other mammals. While evolutionists can, at least superficially, fit observed patterns of similarity into their model, the patterns fit well within the creation model, where a Designer reuses design elements in separate creations and uses patterns of similarity to make the biological world comprehensible.
One evolutionary argument that initially seemed to strongly support common descent of humans and apes was the argument of shared mistakes. Certain sections of DNA are known as pseudogenes. These supposedly contain “mistakes” so they cannot be used to make a protein, and thus were assumed to be useless.2 Since it would not seem appropriate for a Creator to create “mistakes,” it was assumed that mutations preventing the protein from being made occurred by accident. Since it would seem that both apes and humans have some of the same “mistakes,” the most likely explanation appeared to be common ancestry. This is because such a pattern would seem highly unlikely by chance and natural processes alone.
The explanation seemed fine until some pseudogenes were studied in detail and found to have important functions. In fact, one human pseudogene has been shown to code for a functional protein, highlighting the fact that there is much we still have to learn about DNA.3 If pseudogenes have function, this calls into question the idea that they contain “mistakes.” However, there is another problem with the evolutionary explanation: it assumes all genetic changes are essentially random accidents. There is evidence that suggests otherwise.
Creation scientists have found that diversity within created kinds has increased since the time of the Flood, when only two of most animal kinds survived on the Ark. For example, mutations, defined as a change in DNA sequence, have occurred that modify characteristics of hair coat, including its color. In some cases, the pattern of the changes is similar, or even identical, in very different animals. One example is the same change in DNA sequence of the MC1R gene found in cattle, pigs, and an American mink.4 Most evolutionists would consider this convergent evolution, rather than a similarity based on common ancestry. I would consider this and similar evidence a strong indication that there are mechanisms that bias the location and types of mutations that occur.5 The same mechanisms exist in different kinds of animals and can sometimes produce similar, or even identical, results. These changes allow for minor modifications that can be adaptively useful, enabling animals to “fill the earth” as God intended (Genesis 1:22, 8:17; Isaiah 45:18).
Creationists recognize that some similarities can be the result of common ancestry, such as most of the similarities between horses, donkeys, and zebras in the horse kind. Some similarities arose from similar (or even identical) changes in different kinds, such as a black hair coat in cattle and in pigs.6 However, much of the similarity that extends across the animal kingdom is from a Designer who created an amazing world in a way so that we can comprehend much of it. While scientists have already learned an amazing amount about the biological world, it is important to recognize that there is still an astounding amount we have left to learn.
Due to our limited knowledge, it is often challenging to determine the source of specific similarities and differences between animals, but one thing is clear: there is awe-inspiring beauty and variety apparent in living things today. The design God placed within creatures has enabled them to reproduce and fill the Earth. The patterns we see have also facilitated human understanding of biological details, many of which have been used to positively affect the well-being of humans and animals.