Evidence for Evolution

First a disclaimer. I’m an example of a “Theistic Evolutionist”. I think this actually makes me a good candidate to evaluate the evidence for evolution. If the evidence tended to show that God created each species independently, I’d be happy to accept it. I’m not an atheist, so I have no anti-God axe to grind. On the other hand, I don’t believe that the opening chapters of Genesis require me to believe any scientific particulars about the origin of species. So if the evidence tends to show that all life descended from a common source with modification, I’m equally happy to accept THAT. I was originally a zoology major in college, so I have enough of a science background to at least have a basic understanding of most of the ideas presented in favor of evolution. My purpose in this article or articles will be to try to explain these issues to Christians and other theists simply enough that they can evaluate them.

Let’s begin by setting some boundaries.  People mean a lot of different things when they say “evolution”. All I’ll be talking about here is the idea that all life has descended with modification from common ancestors. This is one formulation of the FACT of evolution. Evidence for the truth of this idea is overwhelming. In fact, evidence of the same strength and kind regularly sends people to death row for murder. And I’ll hope to show that if the FACT of evolution is false, then God has gone out of his way to deceive us – to the extent that he could not be trusted.

As to the mechanism of HOW life descended with modification from a common source – that is more open to discussion. We know a great deal about some of the mechanisms, but certainly not everything. As to how life originated in the first place – that is even MORE open to discussion. Scientific theories about this currently rely on substantial amounts of conjecture. What we DO know is that somehow, life descended from a common source with modification. It was not created in the form of distinct individual “kinds” or species, as creationism would have it.

DNA and Genetics

It’s interesting to remember that Charles Darwin knew nothing about DNA. The workings of the inside of the cell were, to use Michael Behe’s term, a “Black Box” to Darwin and other scientists of the day. In Darwin’s day, it was well known that parents (human, animal or plant) passed on their characteristics to their offspring. People with black hair would tend to have children with black hair. Birds with larger beaks would tend to have offspring with larger beaks, etc. Although genetics was studied, no one knew exactly HOW these characteristics were passed on.

Now we know that DNA and RNA molecules control these traits and others by controlling the structure of the proteins that make up the bodies of all living things. The genes on the DNA molecule are blueprints for building the complicated building blocks that make up life. These DNA molecules, and the traits they contain, are passed down from one generation to the next. Enormous effort has gone into studying and cataloguing gene sequences of the DNA molecule, especially in humans. We have also studied the intricate and fascinating workings of living cells down at the level of biochemical reactions.

The Commonality of Life

The first fascinating thing about DNA is that all life on earth uses it. Not only does all life use DNA, but there are other surprising similarities. All life uses the same basic three types of polymers out of hundreds of possibilities. Many molecules that make up life come in “right-handed” and “left-handed” varieties. Overwhelmingly, all life on earth uses molecules of the same “handedness”. All DNA in all life uses only four nucleoside building blocks out of at least 102 possibilities. All proteins in all living things use only the same 22 amino acids out of 309 amino acids available in nature. All life uses the same basic “code” for translating DNA into proteins. All life uses a very similar cycle of complex chemicals to process energy. For example, virtually every form of life from yeast to man uses a protein called “cytochrome c” as part of the process of providing the body cells with energy. When Darwin proposed that all life descended from a common source, he had no idea that at the molecular level, all life would turn out to be so very similar.

Why this similarity? If God were creating each species separately, why would he make a rose and a whale look so completely different on the OUTSIDE – but function so similarly on the INSIDE, at the level of molecules? Why limit himself to so few chemical choices out of the huge number available? Why be so beautifully creative with the outward forms and so boringly repetitive with the inner workings? Did he take shortcuts with the biochemistry because he thought no one would be looking at it?

Of course, it all life descended from a common ancestor, then everything becomes plain. All life has inherited the basic chemistry of life from its original ancestor. If only God had made a few species that use different amino acids, or a different polymer or a different nucleoside – the theory of evolution would be in serious trouble. But he didn’t.

DNA Variation and Mutation

Although normally DNA is passed from parent to offspring as a perfect copy, occasionally there are problems. Minor changes can happen, for various reasons. DNA can be damaged during copying due to such things as radiation, environmental toxins, certain viruses or just a random “hiccup” in the chemical machines that do the copying. There are many sections of the DNA molecule that are inactive. Changes to those parts of the DNA molecule will be passed on to the offspring, but will have no noticeable effect on the offspring. On the other hand, if the mutation happens to a part of the DNA that is used for making proteins, then the protein can be changed. This can cause major or minor differences in the traits of the offspring. Mutations and the rates of mutation have been extensively studied, especially in humans. This is an important part of some cancer research, for example.

Take, for example, the protein “cytochrome c” I mentioned above. This protein is made up of about 100 amino acids and is vital to all life on earth. Because it is so vital, any mutation that seriously changes the way DNA produces cytochrome c tends to be fatal. And for that reason, very few changes in cytochrome c are passed on to offspring. But there are some parts of the cytochrome c protein that are only “structure”. They can be changed to a different amino acid without changing the function of the molecule.

Think of it as a toy dump truck made of legos. The toy truck has to have wheels, and a certain cargo capacity. But it really doesn’t matter, for most of the truck, if you build it out of green legos or black legos, or a mix of all sorts of colors. As long as the structure is there and it rolls and carries cargo – it will work. And so the cytochrome c molecules in humans are slightly different than the ones in horses, or corn, or yeast. They have accumulated some mutations. But they all work. In fact, you can take human cytochrome c and put it into yeast and it will work just fine.

But here’s the interesting part. If any life form has a mutation in its DNA causing a change in cytochrome c, it will pass that change in cytochrome c on to its offspring. If all life is descended from a common source, then, we should be able to map out the family tree of all life on earth by comparing cytochrome c molecules. If we start with humans, then any form of life with very similar cytochrome c should be on a branch of the tree very near us, and any form with more differences in cytochrome c should be farther away. So what do we find? We start with:

Chimpanzee: 100%. That is to say, chimp cytochrome c is absolutely identical to human cytochrome c. This would tend to indicate that chimps are very close to us on the family tree of life.

Here are other species and how similar they are to humans in their cytochrome c:

Mouse: 91.3%
Donkey: 89.4%
Horse: 88.5%
Lamprey: 80.8%
Carp: 78.6%
Maize: 66.7%
S. pombe (a yeast) 67.3%
Neurospora (another yeast) 63.7%
Euglena (a single celled organism) 56.6%

It’s not hard to see that the tree of life we actually find by molecular testing is very similar to the tree that evolutionary biologists had put together decades earlier by examining common characteristics. But Darwin had never heard of cytochrome c. He and other biologists created their classifications based on various shared traits. Darwin did not know that mapping the development of a molecular protein would turn out to show the exact same pattern as his theory predicted.

But how does this fit with special creation? WHY would God deliberately create humans and chimps to have EXACTLY the same cytochrome c out of more than billions of possibilities? Is it because the cytochrome c in humans and chimps functions slightly differently, somehow “tailored” for primates? No. The cytochrome c of virtually all life is basically interchangeable in terms of function. This is because it is basic to the energy cycle of all life. As I said above, human cytochrome c works in yeast without a hitch. Why would God perfectly match his “custom” created cytochrome c to the evolutionary chain of life? Why provide virtually certain forensic evidence that all life evolved from a common ancestor? All God would have had to do would be to give chimps significantly different cytochrome c than humans and evolution would have been dealt a devastating blow.

And cytochrome c sequences basically ARE at the level of importance that DNA evidence is in a courtroom. Cytochrome c differences are caused by DNA differences, and are only passed on by ONE mechanism that we know of in the whole world – one that we observe every single day. Heredity.

Endogenous Retroviruses

If the previous example were not enough, the phenomena of endogenous retroviruses should seal the deal. Retroviruses insert themselves into the DNA of their host. Very occasionally, they will insert themselves into a sperm or ova and will be passed on to the next generation as part of the DNA. Provided that the virus has inserted itself into a portion of the DNA that is not critical, it can and will continue to be passed on for generation after generation. It is estimated that about 1 to 8% of human DNA are these fragments of viruses passed down from our ancestors. These fragments are, in effect, tiny “scars” of ancient viruses infections found on our DNA, in every cell.

Now for the interesting part. Several of these same virus fragments, in the same locations, are found in chimps, gorillas, orangutan, gibbons, and other apes and monkeys. The closer we get to humans, the more fragments are shared. The odds against this being by chance are astronomical. The only known mechanism for having exactly the save virus fragments in exactly the same places is… heredity. It is inescapable that we share ancestors with chimpanzees and other apes and monkeys. We know how the viruses get there. Viral infection. We know how they are passed down – genetically to offspring. These are observable mechanisms that we have studied extensively. Humans and chimps have clear and unmistakable genetic fingerprints of a common ancestor – fingerprints left by an ancient viral infection.

This phenomena is nearly impossible to explain reasonably through special creation. Why on earth would God create both chimps and humans so that their DNA was scared by several virus fragments in the same locations?? What possible purpose could this serve? Why place older and fewer infection markers in more distant evolutionary ancestors – exactly as evolution would lead us to expect? Did God create each of these species so that it APPEARED they had been infected in the past by viruses? Or did he manipulate the odds (and it would have required drastic manipulation) so that they were infected in the same places in their DNA? Either way, God would be going out of his way to LIE to us – to deliberately mislead us with the evidence. And once again, if it had turned out that we shared virus scars with organisms who were very different from us, but didn’t’ share them with apes – evolution would have absolutely no explanation.

If you shared enough very specific gene markers with another person, it would be proof positive in a court of law that you and that person share common ancestry. This is exactly how most paternity cases are resolved. Exactly that same sort of evidence proves conclusively that we share ancestors with the other primates. The only alternative is that God is a liar and a trickster.

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