A Christian's Guide to Evolution

Charles Darwin famously wrote On the Origin of Species by Natural Selection. Those who oppose evolution* generally assume Darwin developed his theory of “descent with modification” based on (limited) fossil evidence.

*Note: I do not call anti-evolutionists “creationists” because I am a creationist too, and I believe humans evolved. As a follower of Jesus, I believed that God, our Father and the Father of our Lord Jesus, created everything through his Son, Jesus Christ. Thus, I am every bit as much a creationist as Ken Ham, as are the millions of other Christians who accept the scientific evidence for evolution.

Darwin’s theory did not arise from fossil evidence. Charles’ grandfather,  Erasmus, had discussed evolution with him from his youth. As a result, when he became a naturalist himself and thus was tasked with classifying life into groups, he was keenly aware of how hard this was. He wrote:

When a young naturalist commences the study of a group of organisms quite unknown to him, he is at first much perplexed to determine what differences to consider as specific, and what as varieties. (Origin of Species, p. 27)

Here we have to stop for a definition. “Consider as specific” means being classified as a species. In the 19th century, scientists classified life by the biblical principal that life reproduces “according to its kind” (Gen. 1:24-25). In Charles Darwin’s day, species was the equivalent of “kind.” Naturalists had to determine whether a group of organisms was specifically created by God or whether they were a later product of (micro-) evolution within that “kind.” If, for example, wolves were a species created by God, then the dogs who descended from them were not a species, but a “variety” or a “subspecies.”

Darwin knew, by experience, how hard it was to determine what was a species and what was a mere variety. Thus, he wrote:

Certainly no clear line of demarcation has as yet been drawn between species and sub-species–that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at the rank of species; or, again, between sub-species and well-marked varieties, or between lesser varieties and individual differences. These differences blend into each other in an insensible series; and a series impresses the mind with the idea of an actual passage. (Origin of Species, pp. 27-28)

If a variety were to flourish so as to exceed in numbers the parent species, it would then rank as the species, and the species as the variety; or it might come to supplant and exterminate the parent species; or both might co-exist, and both rank as independent species. (Origin of Species, p. 28)

He’s saying that if some set of organisms classified as a variety was so successful that they outnumbered the original species they “varied” from, humans might come along later and class them as the species rather than the original, which would be considered the variety.

Darwin then draws the conclusion that any variety, if it grows enough, could be called a species by humans, leading him to suggest that a variety is really an “incipient species.” (“Incipient” means beginning, which I learned long ago in the delightful and educational game of Balderdash.) With “no clear lined of demarcation” between species and subspecies, everyone is just guessing on what groups of organisms were originally created by God, and which are just varieties.

The next classification above species is genus. The plural of genus is “genera,” and these two classifications are where we get “specific” and “generic” from. Darwin goes on to show that the classification of species within the various genera are just as difficult to determine.

I have heard anti-evolutionists argue that if all animals evolved, then why is it so easy to classify them into specific groups (pun intended). The answer is, it is not easy to group life. In fact, it is so hard that Darwin is able to point out numerous disagreements among the naturalists of his day.

Mr. H. C. Watson, to whom I lie under deep obligation for assistance of all kinds, has marked for me 182 British plants, which are generally considered as varieties, but which have all been ranked by botanists as species … Under genera, including the most polymorphic forms, Mr. Babington gives 251 species, whereas Mr. Bentham gives only 112,–a difference of 139 doubtful forms! (Origin of Species, pp. 25-26)

It is this difficulty that leads Darwin backward in time to argue that just as varieties can grow so much that they are classified as species, so species and their subspecies can grow so much as to be classified as a genus. If you follow this idea further and further into the past, it is conceivable that all species of all genera descended from just a few original species.

This is a bold assertion.

It is said that extraordinary claims require extraordinary evidence. Darwin was well aware of this necessity, and he spent about 500 pages showing the extraordinary evidence for his claim. Part of that extraordinary evidence comes from fossils, and Darwin was certainly aware of fossil evidence for evolution, but fossils were not what led him to argue that life came from “descent with modification.”

I will here review some of that extraordinary evidence, but it is important to remember that Darwin’s argument is that life as we see it today, not just as we see it in the fossil record, looks like variation not just between species but even within genera.

Note: In Darwin’s time, the early to mid 1800s, the idea that all the species in a genus evolved from just one species within that genera was extremely controversial. Today, more than 160 years after Darwin published his book, even the anti-evolutionists agree that every species in the genus “Felis” descended from just one “Cat kind.”

Artificial (Man-made) Selection

One of Charles Darwin’s main pieces of evidence was the amount of evolution in species that have been bred by man (which he called “artificial selection”). Darwin chose to use doves as an example, all known or supposed to be descended from the wild rock pigeon. Dove-breeding was, and is, popular in England. Darwin argued that the doves had varied so much from the rock pigeon that any naturalist would classify them into at least 3 genera.

If humans could breed one species into 3 genera, then it shows that each family, the next classification beyond genus, given enough time, could have evolved from one species. If that is true, surely we have to consider that each family in an order, the classification above family could have evolved from one species within its order … and so on up the ladder of classification.

Of course, in the USA, we would choose dogs over doves. That both St. Bernard’s and chihuahuas descended from wolves is almost impossible to fathom. Like England’s doves, it seems obvious that 19th-century naturalists, if they did not know that chihuahuas descended from wolves, would classify dogs into multiple genera.

If you were to read the 500 pages of On the Origin of Species by Natural Selection, you would be in awe of Darwin’s vast knowledge of life, both flora and fauna, both on the earth and under the sea. He explains the possible evolution of many organs, from the crabs’ claws to the human eye using only examples from living species.

Fossils

Darwin did, of course, appeal to the fossil record, primarily focusing on fossils he found in South America as he went around it during his time on the Beagle. I won’t spend much time on this section because, for Darwin, the fossil record only went back tens of millions of years to the time of the “megafauna,” such as the giant ground sloth (link with image).

We now have many more fossils than Darwin had in his day. The lineage of whales can be thoroughly traced back to Pakicetus, a land mammal. The lineage of humans from Australopithecines is so thoroughly represented in the fossil record that it is more of a bush than a line.

The changes in life on the earth are so well-documented by the fossil record in the 21st-century that we can legitimately say that evolution is a fact. Anti-evolutionists like to point out that almost all the phyla (the highest classification below kingdom) were present in the Cambrian period. For example, our phylum, chordata, is already present in strata of the earth that are dated to more than 500 million years ago. Anti-evolutionists ask, “How can you explain that?”

Well, our phylum, chordata, consists of animals that have a backbone, including all fish, amphibians, reptiles, and mammals. Cambrian chordates, though, had only a notochord, a structure made of cartilage that is a precursor of a spine. Wikipedia has photos of fossils from the Cambrian, one of which resembles a guppy and none of which resemble any land animal we know.

If we rely on Cambrian fossil evidence and nothing else, then life on earth evolved over 500 million years from boneless creatures no more than 6 inches long to all the animals on earth that have bones or even shells. This is not a level of evolution that anti-evolutionists admit, so I have no idea why they would want to point out the existence of almost all phyla in the Cambrian period. After all, the only representatives of our phylum, all animals with spines, did not yet have any bones, much less an actual spine.

We call evolution a fact because the fossil record tells us that life has dramatically changed from only single-celled life a billion years ago to the vast array of multicellular life we know today.

The theory of evolution is the attempt to explain how we got from life a billion years ago to life today. The discovery of DNA, a genetic code that is shared by all life, gave us a solid basis for the theory of evolution. Now study can be focused on how DNA has changed over time, because DNA programs life.

Abiogenesis (the origin of life)

There are also theories about how the first DNA and the first cells formed. These theories concern the science of “abiogenesis,” the origin of life. There are numerous theories about how life might have arisen from non-life, none of which are certain, and none of which have anything to do with evolution.

We know that life as we know it evolved because we can document the gradual change from Cambrian life to modern life. We have a pretty good understanding of how that happened. On the other hand, we have only educated guesses about how the first cell arose.

Genesis 1 tells me and many others who accept the fact of evolution and have varying levels of understanding of the theory of evolution that God created everything. Many of us believe God created everything because we have experienced him. Some of us have gotten to know God and his ways through submission to Jesus Christ, proven to be God’s Son by the resurrection from the dead.

Nothing in science can stumble those who know God and are kept by the faithfulness of Jesus Christ and the power of the Holy Spirit.