Did living things come from a common ancestor, or were they created separately?

The title asks an important question. It's also a broad question. Let me re-phrase it, more narrowly:

Do some living things resemble each other because of descent from a common ancestor, or because they were created to be similar?

Some people do not believe that the earth is old enough for there to have been distant common ancestors. They might believe that, say, cows and bison came from a common ancestor, or at least that all the breeds of cows did, but that cows and deer could not have, because there wasn't enough time. Some people, often the same ones, believe that the language of Genesis 1 indicates that God created the varieties of organisms by separate creative acts. Some people, usually the same ones as mentioned above, do not believe that humans and non-human primates share any common ancestry, because they believe that the language of Genesis 1 indicates that humans were created specially from non-living material. On the other hand, there are Bible-believing, God-fearing Christians, who are not so sure of all of this, and believe that the earth is very old. Such people may also believe that God especially endowed some pre-existing primate with the image of God (whatever that is) and that, therefore, non-human primates were distant biological ancestors of humans. Billy Graham has said that that may have been what happened.

If humans and chimpanzees were created separately, then how do people who believe this explain the similarities between the two? In particular, how do they explain the genetic similarity? The usual response is that, in order to function properly, genes have to fall within a narrow range of structural constraints. Therefore, human genes, and chimpanzee genes, were created to be much alike. Although we aren't really sure that there is only one way to make, say, an Oxygen-carrying molecule like hemoglobin, this argument of those who believe in special creation has some plausibility. But not enough.

A recent article, by a scientist who is a Christian, and well-qualified to discuss the matter, examines a situation where genes don't function. And, in this case, vitamin C production, it turns out that non-functioning genes of humans and non-human primates are very similar. The only reasonable explanation seems to be that humans and non-humans inherited their genes for vitamin C production from an ancestor which had lost the capacity to produce enzymes that could synthesize vitamin C. Thus neither humans nor orangutans can produce vitamin C, but both have the apparent remains of the genes that produced it in the presumed common ancestor, and these remains are almost identical.

Thanks for reading.

Pi day - on the ratios of similar shapes

Today, March 14, or 3/14, is celebrated by some, especially by schoolteachers, as pi day. The reason is that 3.14 is an approximation for pi. Why isn't 3.14 pi?

Pi is the ratio between the circumference, the distance around, and the diameter, the distance across, of a circle.

Let's consider a seemingly unrelated topic. Suppose you think about someone you are very familiar with, someone you have seen many times in current photos. Perhaps yourself, perhaps someone else. Can you recognize that person in a small photo, as well as a large one? Of course, unless the photo is so small that you can't make out details at all. Why is that so? The photos are different, yet they are all of the same person, and they are similar. Similar in what way? Several ways, such as eye color, perhaps, but they are similar in many ratios. The distance between that person's eyes, in the photos, has the same ratio to the distance from one corner of the mouth to the other, in every photo. The distance from one corner of the left eye to the tip of the nose has the same ratio to the distance from one corner of the right eye to the tip of the nose, in every photograph. You haven't measured these distances, or calculated the ratios, but if these, and many other ratios, weren't the same in each photograph, you would start to think that some of the photographs weren't of the same person. (For a person's face, we need to allow some leeway for whether they are smiling, the angle that the photo was taken from, and the like, but the ratios need to be close to the same, or the same, for the photo to look natural.)

One more example. Consider squares. Are all squares the same size? No, of course not. But all squares have some ratios that are identical, or they wouldn't be squares. Most obviously, the ratio between any one side of a square, and any other side, is 1. The sides are all identical. Another ratio of all squares is the ratio between any side and the distance from one corner to the opposite corner. That ratio can be determined by the Pythagorean Theorem, which tells us that the sum of the squares of the shorter sides of a right triangle is equal to the square of the hypotenuse, the longest side. From that, the ratio of the distance across a square, from one corner to an opposite corner, to a side of that square, is equal to the square root of 2. Always, for all squares.

So a person's picture always has the same ratios, or nearly so, between dimensions. A square always has exactly the same ratios between various dimensions. Circles, too, are all similar, regardless of size, meaning that the ratios of their dimensions are the same. What ratio? What dimension? The ratio between the distance around any circle, the circumference, to the distance across the circle, through the center, which is the diameter, is always the same. And that ratio is pi.

It so happens that pi (and also the square root of 2) are irrational numbers. That is, even though they are ratios, they cannot be exactly expressed as ratios between whole numbers. Pi is nearly 22/7, but not exactly. Pi is nearly 3 and 14/100, but not exactly.

For much more on pi, see the Wikipedia article.

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.

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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.

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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.

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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.