Microevolution

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=== Targeted variation ===
 
=== Targeted variation ===
Contemporary creationists point to the non-random nature of variation to differentiate between microevolution and macroevolution.  For example, the genes involved in determining height, intelligence, build, and skin color vary a great deal between generations, while the genes involved in managing cellular functions vary little if at all.  They point to this non-random variation as evidence that life's capacity for variation was ''designed'' to vary the genetic code where variation is advantageous, and not vary the code where such variation is disadvantageous.
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Contemporary creationists point to the non-random nature of variation to differentiate between microevolution and macroevolution.  Specifically, recent research has shown that genetic variation occurs primary in "hotspots," and not in "cold-spots" within the genome<ref>[http://www.pnas.org/cgi/content/full/97/21/11383] [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1207851]</ref>  Creationists infer from these facts that certain areas of the genome are ''designed'' to vary, while others are not.  For example, they argue that the genes involved in determining height, intelligence, build, and skin color vary a great deal between generations, while the genes involved in managing cellular functions vary little if at all.  They point to this non-random variation as evidence that life's capacity for variation was ''designed'' to vary the genetic code where variation is advantageous, and not vary the code where such variation is disadvantageous.
  
 
==References==
 
==References==

Revision as of 20:41, 16 February 2008

Microevolution is a term — when used by creationists — that is the evolutionary equivalent of the belief that the mechanism you use to walk from your bedroom to the kitchen is insufficient to get you from New York to Los Angeles.

Contents

Critical description

Microevolution is a concept generally used by creationists to denote evolution within a species, or adaptation. The reason that creationists even use the term at all is that they feel the need to provide some mechanism to explain the variations observed in the animal kingdom, when they also subscribe to the view that not all life on the planet is related via variation and natural selection.

Given that many creationists lack faith[1], they then require the support of science to validate their worldview, and science cannot support the unfeasibly large wooden vessel required to save the plethora of varieties within each species we see today, as well as the obviously large number of species that are now extinct, but which creationists claim were extant at the time of the flood and have since died out. Thus they fall back on kinds and microevolution to salvage any pretension of scientific rigour. For example: If only two of the cattle kind are required on the ark, all they then need is to explain how those two animals can be responsible for the diversity of cattle we see today, and microevolution is their chosen explanation.[2] Chosen, perhaps, in the mistaken belief that if science attacks their concept it will effectively be attacking the whole concept of evolution. They care little that the rate of evolution required to account for their beliefs is orders of magnitude greater than any rate proposed by science, even for periods of great species diversification such as the Cambrian Explosion.[3]

However, they then need to be careful not to allow one species to be descended from another -- which concept they term macroevolution -- and propose that there are mechanisms that stop this from happening. Thus far, no creationist, of a scientific bent or layman, has ever proposed just exactly what those mechanisms are, nor have they provided one data point to support their idea.[4] Their only justification for their position is wishful thinking and as yet, in spite of their best efforts, very few people are willing to allow wishful thinking to be considered scientific evidence.

Whilst not commonly used by scientists, when they do use it the word microevolution means much the same thing that creationists mean, but without any suggestion that microevolution is anything but plain old evolution, and the only thing that seperates "micro" from "macro" is time.[5]

Support perspectives

Creationists themselves would disagree with the characterization of their views as stated above. Creationists differentiate between microevolution and macroevolution based on their belief that life forms have the capacity to vary to some degree, but within limits. These limits are caused and evidenced by the following:

Irreducible complexity

Contemporary creationists argue that evolution is limited in that it cannot lead to the formation of new "irreducibly complex" systems. Thus evolution may cause a species' heart to grow stronger due to natural selection, but it cannot cause the development of the heart itself in a step-wise manner, because all the component parts of the heart must have been in place simultaneously in order to function at all. Creationists make similar arguments with respect to many systems, including the eye, the nervous system, blood clotting, cilia, and origination of life itself, abiogenesis.

Specified complexity

Contemporary creationists argue that evolution is limited in that it cannot lead to an increase in the amount of information contained in the genetic code. Various mathematical arguments are made along this line by people like William Dembski.

Devolution

Contemporary creationists generally believe that life immediately after the flood was more heterozygous than life today. However, through the process of variation and natural selection, lifeforms became more homozygous due to natural selection and genetic drift. Thus the original people were heterozygous with respect to racial characteristics, but natural selection and genetic drift caused the races to differentiate, as white skin has an advantage in the temperate (and polar) climates, and black skin has an advantage in the equatorial climates. Consequently they would argue that white skin did not evolve with mutations among an originally black population, but rather black skin and white skin devolved from an original race with the genetic characteristics of both.

Creationists make similar arguments with respect to many species. For example, lions and tigers may have devolved from a primeval liger as each lost the genetic characteristics of the other due to to natural selection and genetic drift, or camels and llamas may have devolved from a primeval cama in the same way. Of interest to many RationalWiki editors, goat and sheep can occasionally produce a hybrid. While most of such hybrids are stillborn, one living sheep-goat hybrid was known as the "Toast of Botswana".

Targeted variation

Contemporary creationists point to the non-random nature of variation to differentiate between microevolution and macroevolution. Specifically, recent research has shown that genetic variation occurs primary in "hotspots," and not in "cold-spots" within the genome[6] Creationists infer from these facts that certain areas of the genome are designed to vary, while others are not. For example, they argue that the genes involved in determining height, intelligence, build, and skin color vary a great deal between generations, while the genes involved in managing cellular functions vary little if at all. They point to this non-random variation as evidence that life's capacity for variation was designed to vary the genetic code where variation is advantageous, and not vary the code where such variation is disadvantageous.

References

  1. By which we mean irrational belief in that for which there is no evidence, as opposed to the Judaeo-Christian understanding of faith as commitment to what one "knows" to be true
  2. In fact, Genesis clearly states that seven pairs of all kosher animals were brought on board, allowing for 28 distinct chromosomes of genetic information in the cattle baramin. Dogs and cats are another matter.
  3. Because they explain diversification of species in terms of "devolution," or the loss of genetic information from heterozygous created kinds.
  4. Except for the four unsupported proposals cited immediately below
  5. Evolution 101
  6. [1] [2]


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