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Tuesday, September 13, 2005

I believe in evolution. So do you!, part 1

I believe in evolution. So do you!
I hope that got your attention. Please read on.
A statement like the first sentence in the title should force the reader to ask a question: "What do you mean by evolution?" (The same question should have been asked, if that first sentence had said: "I don't believe in evolution.") All too often, the question isn't asked, and confusion results. This topic has generated a lot of discussion, and will generate more after I am long gone. Some of the discussion is because of genuine disagreements. But, unfortunately, some of it is because people aren't careful to define their terms.

One meaning of the word, evolution, is change. If that's the meaning, everybody believes in it. Transportation, for example, has evolved from walking and being pulled, or carried, by beasts of burden to bicycles, scooters, trains, automobiles and airplanes. No doubt there will be further evolution, in this sense.
The Bible indicates that all humans descended from a single couple, Adam and Eve, or from a single family, that of Noah and his sons and their wives. Humans are not nearly as homogeneous as they were in the time of Adam and Eve, or of Noah and his wife. That means that humans have evolved into various racial groups.

Another meaning is natural selection. Charles Darwin proposed the notion of natural selection. He noted that there was considerable variety in the offspring of a single pair, and that there weremore offspring born (or hatched, or sprouted) than survived. He also noted that offspring resemble their parents. Those facts led him to propose that there is a struggle for existence, that the most fit survive, and that they leave more offspring in the next generation than those who aren't so fit. I have never read anyone who understood it who doubted Darwin's facts, or his conclusion. Natural selection is a fact. It is probably at least partly responsible for the variety of humankind. It is almost certainly responsible for the frequencies of the sickle-cell anemia gene in various populations. It is responsible for antibiotic-resistant bacteria, and insecticide-resistant insects.
Artificial selection is when humans decide what individual domestic animal or plant is going to reproduce, because they want to get a certain type of offspring. Selection by humans works, and works well. An enormous variety of selective experiments have been done, sometimes by scientists, sometimes by farmers, or people raising animals or growing plants. You can select just about any species for just about anything. The mechanism of artificial selection isthe same as that proposed by Darwin for natural selection.
Darwin himself didn't seem to realize it, but the most important result of natural selection isn't change, it's stability. Organisms don't change very much over time, not because their offspring are all alike, but because departures from the norm are selected against.
So if everybody believes in selection, what's the big deal? Well, one reason is that there are other things people sometimes mean when they use the word,evolution.

Yet another meaning is speciation. The short title of Darwin's book was The Origin of Species. Speciation is those processes which lead to the appearance of new species. Here's where we hit a couple of the big deals. One big deal is the use, in the King James Bible, of the phrase, "after his kind." Some people think that that rules out speciation, the creation of new species. The fact is that, whatever "kind" meant, it is a concept of God, and we aren't sure what it meant. Species, and other categories of taxonomy, are human constructs, and don't necessarily correspond with "kind." (For all we know, cat kind included lions, leopards, and domestic cat-like animals.) Since these are human constructs, they are changeable. Darwin believed, and most biologists also do, that the mechanisms of natural selection, as described above, are responsible for the development of new species.
Can a Christian believe that new species arise by natural selection? Clearly, some do, and some don't. If the world is only about 6,000 years old, there hasn't been enough time for much speciation. If God created the variety of living things by miracles, then they didn't get here by natural selection operating on previous forms. There are Christians who believe that the world is about 6,000 years old, and some who believe that it is much older. Even if it is very old, of course, that doesn't prove that the species we have arose by natural selection, but it would make that possible. There are Christians who believe that God created basically all the species we have now, during a short period of time. There are Christians who don't. All flavors of belief about these matters can be found, although most people don't realize this.
My own view is that at least some speciation has occurred since the beginning. Even the most literal interpretations of Genesis don't rule all speciation out, in my opinion. However, they rule out the possibility that most species arose in this way. Therefore, many Christians do not believe in evolution, if by evolution is meant speciation.
The second big deal relates to humans. Did we arise from some previous species by natural selection? The Bible seems to indicate that humans were created by a miraculous process. The Bible indicates that humans are different, and the God treats them differently, from other organisms. God gave us dominion over the rest of them (Genesis 1:26, 28) and God came as a human,Jesus Christ.
(Lest there be any doubt, no reputable scientist believes that humans evolved from chimpanzees. Many scientists believe that humans and chimpanzees share a common ancestor.)
Some Christians believe that the first part of Genesis is not meant to be taken literally. They can accept that God may have used some process to produce humans out of non-humans, and that our bodies, at least, evolved from some pre-human stock. Many Christians do not accept this, and, therefore, do not believe in evolution, if by evolution is meant the origin of humans from non-humans by partly or entirely natural processes.
The scientific evidence for speciation, including that of humans, is, in a word, similarity. All animals have cells, and are alike in other ways. All mammals, including humans, are similar in several ways. Chimpanzees and humans look enough alike that chimps are sometimes dressed in human clothing. The two species share 96% or more of their DNA. I believe that the Bible teaches that evidence from nature, including the findings of science, must be taken into account. (Psalm 19, Romans 1:20, Acts 14:17) If we knew how to correctly interpret the Bible, and how to correctly interpret scientific findings, there would be no conflicts. We don't know how to correctly do either, and sometimes there are conflicts.
To be continued, God willing. (See here for the second part, here for the third.) If you really have too much time on your hands, click on the origins label at the end of this post!
Thanks for reading.

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