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Thursday, April 10, 2008

The many meanings of "evolution" - no wonder we get confused!

One thing that confuses people who are trying to follow the intelligent design controversy is that the word "evolution" is used by different people to mean strikingly different things. Embryologist Jonathan Wells notes,

"Evolution" has many meanings. It can mean simply "change over time." The present is different from the past. The cosmos evolves. Technology evolves. No sane person denies evolution in this sense.

In biology, "evolution" can also refer to minor changes within existing species. Nobody denies evolution in this sense, either. People were observing such changes for centuries before Darwin came long; they were even producing them in plants and animals by artificial selection. Darwin (and Wallace) pointed out that something analogous to artificial selection operates in natural populations, but there is nothing "Darwinian" about artificial selection.

Lest some people mistakenly conclude that I accept Darwinian evolution broadly defined, I will make two other distinctions. The first is between "microevolution" and "macroevolution," and the second is between "macroevolution" and "Darwinism."

Regarding the first: Almost eighty years after Darwin published The Origin of Species, neo-Darwinist Theodosius Dobzhansky noted that there was still no hard evidence to connect small-scale changes within existing species (which he called "microevolution") to the origin of new species, organs and body plans (which he called "macroevolution"). Dobzhansky wrote: "We are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of macro- and microevolution, and proceeding on this assumption, to push our
investigations as far ahead as this working hypothesis will permit."

1. Unfortunately for Darwin, there has never been a confirmed case of natural selection producing a new species, much less new organs or body plans

2. So in 2008, seventy years after Dobzhansky and a century and a half after Darwin, the extrapolation from microevolution to macroevolution is still just an assumption.

Concerning the second and final distinction: Darwin didn't just claim that natural selection could produce new species, organs and body plans. He went much further and argued that (a) all species are biologically descended from a common ancestor, and (b) their features were produced entirely by unguided natural processes. He wrote: "There seems to be no more design in the variability of organic beings, and in the action of natural selection, than in the course which the winds blow."

3 It is the claim of universal common ancestry coupled with the exclusion of design that I call "Darwinism."

So "Darwinian evolution" can mean changes in existing species ("microevolution") due to natural selection. This is what Egnor referred to as "obviously true," and I agree. But for some people "Darwinian evolution" also includes the extrapolation from microevolution to macroevolution. This is far from obviously true; indeed, the evidence for it is underwhelming, at best.

Actually, natural selection tends to conserve, not create.

See, for example, Thoroughbred by Design? Mustang by Chance?


Natural Selection: Tracking the Primitive Dog

to see how natural selection works in horses and dogs.


Scientists shocked: First animal complex, not simple

LiveScience outlines the shock that the comb jelly administered to scientists recently.

Early life researchers had assumed that sponges appeared first because they are so simple. A research team headed by Casey Dunn of Brown University in Rhode Island determined that the much more complex comb jelly came first. Which means that ...

Unlike sponges, comb jellies have connective tissues and a nervous system, and so are more complex. Though squishy and tentacled, they are not, however, true jellyfish as they lack the classic bell-shaped body and characteristic stinging cells.

The finding was unexpected because evolutionary biologists had thought that less complex animals split off and evolved separately first.

All this shock and awe comes from not taking the Avalon explosion and the Cambrian explosion of life forms seriously for what they can tell us about the real history of life, rather than the Darwinian fantasy.

(In fact, the Smithsonian secretary tried to bury the Cambrian explosion in the vaults in the basement.)

Evolutionary biologists are still looking for the long, slow upward plodding path that life never took.

Incidentally, the LiveScience staff note,
Though comb jellies are a common creature in the seas today, these modern specimens likely look very different from their early ancestors.

Don't count on that either.

A few years back (2004), I wrote an item for a science teachers' magazine, "Time Stands Still for Shell Guy?", detailing an equally remarkable discovery: An early crustacean that had fossilized so quickly in Herefordshire, United Kingdom, that its internal body plan was actually preserved.

The team led by David Siveter of the University of Leicester were able to completely reconstruct the fossil, a rare event: A recently found 425 million-year-old fossil crustacean apparently has the same internal organs as a modern one. Most news items on this find focused on the fact that Colymbosathos is the oldest “male” fossil (= the penis was visible). But the real story, for science, is the amazing stability of the key crustacean body organs over so vast an expanse of time.

Researchers working with Siveter found the ostracode in Herefordshire, and discovered that it has quickly mineralized, so that most of its body tissues were preserved. They seized the opportunity to shave the rock very finely and photograph all the shavings, which enabled a complete reconstruction - and pushed back knowledge of the group by 200 million years.

And what did they discover? "Researchers are puzzled as to why the ancient creature appears so similar to its modern relatives."

Sigh. To the extent that researchers simply try to confirm what they think must be true, they will just go on being "puzzled" every few years.

See also:

Biology's Big Bangs

The Avalon explosion: The dawn of life reveals yet another intricate puzzle

Critical Decisions in Science: The Smithsonian Secretary versus the Cambrian Explosion

Questions in Evolution: Animals suddenly appear and after that nothing much happens. Why?


Today at the Overwhelming Evidence blog

Group vs. individual selection - left wing vs. right wing biology?

Intelligent design films on the Internet

Wars on science? Hey, we are all anti-science now

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