Daily Kos is a primarily political blog, and a diary about evolution might seem like a distantly related side issue. Nevertheless, I think it useful for educated people to understand the world around them. A firm disclaimer is in order: I am not now, nor have I ever been, an evolutionary biologist, or even a genuine scientist of any kind. I am merely an interested layman who has a keen interest in the subject. Further, there are certainly Kossacks more qualified that I am to explain the subject; maybe this diary will induce some of them to comment.
Oh, and stick around for the political rant at the tail end!
Please join me below the orange squiggley.
When the layman hears the word "evolution", it almost always brings to mind the phrase "survival of the fittest". But this phrase, while expressing an important idea in biology, does not define evolution any more than the Pythagorean theorem defines geometry. Biologists define evolution as genetic change over time. It is an undeniable fact that this occurs, but it almost seems like the biologist is deliberately choosing a definition that cannot be challenged.
This is not the case; the fact of evolution is a simple observation, just like the fact of gravity. Just as the theory of gravity is a different concept from the fact of gravity, the theory of evolution is not the same thing as the fact of evolution. Organisms do change over time.
Perhaps the most striking example is the domestic dog, which has evolved only recently in geologic terms. Although almost identical genetically to the gray wolf, the dog is probably best thought of as a separate species. It has adopted mankind as a lifelong partner, and mankind has adopted it. It is reproductively isolated from its wolf ancestors by its partnership with mankind, probably forever. The dog illustrates the fact that the word "species" is arbitrary and artificial. In the real world, the distinction is almost meaningless.
When scientists use the word theory, they are not using the word the way English speakers frequently use it. "Theory" does not mean "guess" or "conjecture" or "hypothesis", it refers to a detailed and coherent explanation. The theory of evolution (ToE) explains a great deal about the world of biology. It is about a myriad of details so numerous that the layman can get lost trying to understand even the broad outlines.
A key conclusion of ToE is that all living things are descended from a common ancestor. For example, a polar bear and a raspberry bush are both descended from the same species. It may come as a great surprise to learn that at the biochemical level, polar bears and raspberry bushes are extraordinarily similar. In fact, their common ancestor was likely a single celled organism about 800 million years ago, +/- 200 million years. That organism was a eukaryote; that is, it had a complex cell structure with a separate nucleus. It had not yet differentiated into the branches we now call animals and plants and fungi.
Common descent is a conclusion that flows naturally from the facts. Every single organism in nature has, as its probable ancestor, an extremely similar and usually simpler organism. This is what biologists call the nested hierarchy, or more commonly and popularly, the tree of life.
This nested hierarchy is powerful evidence of common descent. When we find fossilized remains of organisms, we can date them by using several methods. The most common of these methods is radioisotope dating. There are a number of different isotopes used, depending on the time scale in question. This science is quite detailed, and very well established. Suffice to say that we can, with a very high degree of confidence, establish dates for nearly all the fossils we find.
Here's the conclusive evidence: every single one of the millions of fossils found fits in the nested hierarchy, as does every living organism. Every one. If we ever found a fossilized rabbit in the Cambrian stratum, common descent would be falsified, and the theory of evolution would be overturned.
But the evidence for common descent is even more compelling. The DNA of species that appear to be related on the basis of morphology (body plan) show a striking similarity. The most common example is the similarity that exists between humans and chimps. There are obvious and striking similarities in body plan, and the DNA of the two species is also strikingly similar--something like 97%. So we now have a twin nested hierarchy: morphological and genetic.
Humans are more closely related to polar bears than to raspberry bushes, both morphologically and genetically. And yet, all three have a common ancestor. Common descent is, for all practical purposes, a firmly established fact. But how did it come about? How does the genome--the DNA--of an organism change?
On a technical level, the genome can change as a result of ionizing radiation or from the action of certain chemicals. Our DNA is reproduced almost perfectly, but occasionally mutations occur. If they are deleterious, the organism probably doesn't survive. (Survival of the fittest.) But in order for a new species to emerge, what sort of changes must occur? If an ape gives birth to a human male, for example, where does that first man find a mate? This is a question creationists sometimes ask, and they think it's a clever rebuttal to ToE. Instead, it merely displays their ignorance.
This is a bit like wondering how the first person to speak Italian understood his Latin-speaking parents. The right mental picture is to realize that individuals don't evolve, populations evolve. Human populations evolved from populations of ape-like primates gradually, just like the Italian language evolved from Latin gradually. But why did Latin evolve into Italian on the Italian peninsula, into French to the Northwest, and into Spanish on the Iberian peninsula? The answer seems to be, at least in part, geographic isolation. France is separated from Italy by the Alps, Spain from France by the Pyrenees. Isolated from one another, languages drift apart. In like manner, species, when isolated reproductively, drift apart. In fact, it's called genetic drift.
This explains why Darwin's finches on the Galapagos islands are different from their ancestors on the mainland. True, there were environmental pressures that accelerated their evolution. But even without such pressures they would have drifted apart because of reproductive isolation.
I hope this brief overview of evolution has stimulated an interest in the subject by fellow Kossacks. For further reading online I would suggest:
The Talk.Origins website.
Sandwalk -- Larry Moran's blog
Why evolution is true -- Jerry Coyne's blog
Pharyngula -- PZ Myers' blog
What does all this have to do with politics? Plenty. The forces of evil and darkness seek to teach our children the pseudoscience of creationism in our public schools. These days, it goes by the name of Intelligent Design, and its proponents are commonly referred to (by real scientists) as IDiots. They have been consistently defeated in court in their attempts to teach our children superstitious nonsense, but continue to snipe about at the fringes with a policy of intimidation. They intimidate teachers, school boards, text book publishers, and state governments. They have succeeded, especially in the Bible belt, of muting the voice of science.
It is no coincidence that every one of the current crop of Republican candidates is either an active IDiot, or at least sympathetic to them. This is part and parcel of the agenda of the far right to transform America into a theocratic state of their own liking. (If that sounds paranoid, Google "dominionism") An integral part of that agenda is the implacable persecution of the LGBT community, and of its insistence that reproductive issues ought to be regulated by the government. Read this article and then try to tell me there's nothing to worry about. In particular, play the video near the end.
I am aware that many--perhaps a large majority--of Kossacks are religious. I encourage you to make common cause with the freethought community. We are your friends in matters of public policy, almost to the very last one of us.
How did this science diary turn into a political rant? I guess it just evolved ...