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Two Supposed Examples of Darwinian Evolution

Looking for proof of evolution? Biology textbooks frequently cite two examples to show that Darwinian evolution can take place in the real world.

The first commonly offered example involves a species of moths in 19th-century England. The species had two varieties, one light-and the other dark-colored. For years the lighter variety predominated, since its coloration more closely matched the bark of trees on which it rested.

However, as soot from many factories gradually darkened the tree bark, the lighter moths stood out against the now darkened tree trunks. Birds could see the light moths better and soon devoured most. Before long the darker moths, being better camouflaged against the darker bark, became the more common variety.

"In fact this is the first direct evidence actually obtained," says a biology textbook, "to support Darwin's theory, that natural selection occurs" (Contemporary Biology, 1973, p. 567). Convincing evidence-or is it?

This actually might have been a case of Darwinian natural selection changing the species to confer a survival advantage-if the light moths had turned into dark ones. But no such thing happened. In fact, both types were already in existence. The lighter moths didn't evolve into darker moths. They were eaten. The proportion of dark moths increased while the light moths decreased.

As a science publication admitted:

"Students should understand that this is not an example of evolutionary change from light-colored to dark-colored moths, because both kinds were already in the population" (Science Framework, 1990, p. 103).

So nothing new came into existence. What changed was not the moths themselves, simply the proportion of the types of moths. It is ironic that now, with stricter regulation of industrial pollution, the light-moth population has made a dramatic comeback. Yet this supposed proof of evolution at work is still included in many biology textbooks.

The second commonly cited example deals with finches found in the Galapagos Islands. No less an authority than Darwin himself was the first to offer them as an example of evolution in action.

Darwin measured the beak sizes of the finches and noticed a slight difference of the birds' beaks from one island to the 'next. He wrote:

"Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends" (from Darwin's The Voyage of the Beagle, quoted in Contemporary Biology, 1973, p. 560).

This was taken as a living proof of "evolution in action," as Julian Huxley called it.

But was it? In reality, nothing new has been created in the varying beak sizes of the finches. However, the finches' beak size and shape varied-somewhat according to environmental conditions and a division of the gene pool through geographic distancing.

For instance, in 1977 a major drought occurred in Daphne, one of the Galapagos Islands. While many finches died, researchers noticed the next generation, offspring of the survivors, had beaks 4 to 5 percent larger. Their stronger-beaked parents had been able to open the last remaining tough seeds that remained in the island. The bigger-beaked survivors produced a generation of bigger beaked offspring that inherited their parents' characteristics.

Then, in 1983, torrential rains caused flooding in the same island. Now there was an abundance of smaller seeds, and over time scientists found the beak sizes of the island's finches had diminished somewhat, adjusting to their different food supply. Now birds with small beaks could compete for food just as easily, and more smaller beaked finches survived to produce offspring.

But is this Darwinian evolution in action or something else?

This adaptation within the species is called microevolution. It is the same phenomenon at work when the average height of men and women increased by several inches in the Western world over the course of the 1900s. Better health and nutrition played a large part in producing larger-sized people. In the same way, microevolution is at work when breeders produce varieties ranging from Chihuahuas to Great Danes from the one species Canis familiaris-the domestic dog.

These examples show, as in the rest of nature, that all species do have a margin of change available within their genetic pool to adapt to conditions. This trait is found in man, who can adapt to freezing weather, as the Eskimos do, or to the broiling sun in the desert, as Bedouins have done. But Bedouins and Eskimos are still human beings, and if they changed environments again eventually their offspring would also go through minor changes to better adapt to their new environment.

What has never been scientifically demonstrated-in spite of many examples of wishful thinking-is macro evolution, or the change from one distinct species to another. Dogs have never evolved into birds or human beings.

Phillip Johnson goes to the heart of the matter:

"Critics of evolutionary theory are well aware of the standard examples of microevolution, including dog breeding and the cyclical variations that have been seen in things like finch beaks and moth populations. The difference is that we interpret these observations as examples of the capacity of dogs and finches to vary within limits, not of a process capable of creating dogs and finches, much less the main groups of plants and animals, in the first place. . .

"As any creationist (and many evolutionists) would see the matter, making the case for 'evolution' as a general theory of life's history requires a lot more than merely citing examples of small-scale variation. It requires showing how extremely complex biological structures can be built up from simple beginnings by natural processes, without the need for input or guidance from a supernatural Creator" (Reasoning the Balance, p. 74).

So these two supposed examples of evolution at work are really no proof at all of anything-much less how any of these creatures-moths, dogs, finches or humans-came to exist.

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