email - June 2003

Allele Frequency

Subject: Horses and Peppered Moths
Date: Tue, 15 Apr 2003 06:12:47 -0400
From: "Amy”

Dear Do-While Jones,

I read your essay on Horses and Peppered Moths and I am a bit confused. In your case against evolution you are supporting evolution. In your essay you write, “Even if the ratio of light to dark moths did change, it would not be evidence of Darwinian adaptation. It would not have shown that environmental factors cause acquired characteristics to be inherited. It merely would have shown that if you start off with a population consisting of two colors, and kill off most of one color, you end up with a population that is predominantly the other color.” That statement perfectly supports the theory of evolution.

Evolution is only concerned about the change in allele frequency in a population. In this case the ratio of light to dark moths changed which changes the allele frequency. That would be an example of evolution. The ideas you state as Darwinian ideas resemble Lamark’s ideas. Lamark stated that the traits one acquires in his/her lifetime can be passed on to offspring. The theory of evolution states that the environment presents challenges where one genotype may be beneficial over another genotype. If more individuals of the beneficial genotype survive and reproduce, those alleles will be more abundant in the population. That change in allele frequency is evolution. Darwinian evolution does not suggest that one environmental stressor triggers the evolution of a new species. Instead, the environmental stressor changes allele frequency in some way, thus changing the population.

Thanks for taking the time to read my views. If you have time I would be interested in your comments.

Thank you,

Amy

We are glad to clear up the confusion, which stems from the fact that the term “evolution” is used to mean many different things. If “Evolution is only concerned about the change in allele frequency in a population,” then there would be no confusion, and no disagreement. The problem is that people rarely mean that when they use the term, “evolution.”

Some readers might not be familiar with the terms, “allele” and “genotype”. We will run the risk of oversimplifying the details in order to make the general concept easier to understand.

There are genes for making human eyes, but not everyone’s eye genes are exactly identical. There are different variations (alleles, or genotypes) of eye genes. One allele makes brown eyes. Another allele makes blue eyes. Another allele makes green eyes. Alleles are normal variations in genes.

In a randomly selected human population, a certain percentage of people will have brown eyes. Some will have blue eyes. Others will have green eyes, etc. The colors of their eyes are visible indications of what eye-gene alleles they have. So, by counting the number of people with each eye color, one could determine the frequency of each allele in the gene pool.

Suppose we did something to remove people with brown eyes from the population. Then the percentage of blue-eyed and green-eyed people would increase. In other words, the frequency of the blue-eye allele would increase. The population would evolve into one with fewer brown-eyed people, and more blue-eyed people.

There is no argument that demographics can change. Creationists agree that populations can evolve. Natural selection (at least partially) explains how the percentage of light or dark moths can change in a given population.

The confusion comes when someone then tries to use the term “evolution” to mean the creation of moths from non-moths. That would require brand new, fully functional genes, with previously unknown information, to arise. That is an entirely different process than merely changing the relative percentage of existing things.

The primary difference between Lamark’s and Darwin’s views of evolution is one of mechanism. It is generally said that Lamark believed that some conscious desire or decision caused a genetic change in the genes which was inherited. For example, a giraffe’s desire to be taller to reach higher leaves in a tree, triggered a change in the giraffe’s genes which resulted in a longer neck. Lamark may not have actually believed that. There is some disagreement about whether or not the French word Lamark used was properly translated into English. But Lamark was not entirely clear on the process, so Darwin probably believed that Lamark thought evolution was the result of conscious volition.

Our essay, Darwin’s Scorecard (January, 2002), documented the evolutionary process that Darwin presented in The Origin of Species. Darwin thought that diet, exercise, and climate-rather than conscious volition-were the factors that caused genetic change.

Both Lamark and Darwin believed that acquired characteristics were inherited and accumulated over time. So, the primary difference between Lamark and Darwin was the mechanism that caused the acquired change. Darwin went beyond Lamark by saying that natural selection preserves beneficial changes.

Modern evolutionists know that diet, exercise, and climate, affect acquired characteristics, which are not inherited. So, they look for another mechanism for evolutionary change. Modern evolutionists generally take the neo-Darwinian position that mutations are that mechanism.

Amy very accurately describes the modern neo-Darwinian view (also called “modern synthesis”), but incorrectly attributes it to Darwin. Darwin really did write that environmental stress (i.e. climate) is one of the triggers that cause evolution. Modern synthesis says that random mutations create new alleles, and that environmental stress uses natural selection to change the frequency of alleles, just as Amy says.

As Amy says, our statement about the changing demographics of a population “perfectly supports the theory of evolution,” if one uses her definition of evolution. Microevolution (the variation of existing species), certainly does occur. A mutation of an eye gene might cause someone to be born with orange eyes. But this is simply a minor change in an existing gene, with a corresponding minor change in a physical feature.

The argument is not about whether or not eye color can change (i.e. microevolution). The argument is about where the eye gene came from in the first place (i.e. macroevolution). Evolutionists try to argue that lots of little changes in existing genes will create a change big enough to be considered to be an entirely new gene with a different function. The argument is about whether or not the offspring of cows or wolves can evolve into whales if they spend enough time in the water.

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