microevolution

Microevolution is a shibboleth of creationists who are fighting a rearguard action against evolution theory. They claim that animals are divided into 'kinds', which are distinct artefacts of divine creation, and evolution only takes place within each kind. Use of this theory is usually accompanied by a complete misunderstanding of the evolutionary timescale in order to accomodate Noah's Ark. Macroevolution, as the fundamentalists label classic evolutionary theory, is, they say, a lie.

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jmc: The flaw in your logic is obvious, I'm afraid. You're (1) arguing from unfounded axioms and (2) assuming your result.

Aim: ... compelling proof ... that microevolution cannot actually create new species...

Axiom: The process of microevolution can only result in changes within a species. Therefore...

Of course, the real problem lies in the assumption that species are discrete entities. To assume so is to deny the existence of speciation at all, which immediately implies that all extant species have existed in some form at all times in history, and that any extinct species either also so existed, or are in fact parts of extant species. Either that, or it is possible in a single generation for the 'speciesness' of a population to change, which is not borne out in fact.

Microevolution is a term used by evolutionary biologists to refer to small scale changes within a species. Fields such as population genetics or evolutionary ecology are typically concerned with microevolution. All of our many examples of evolution in action are examples of microevolution. Microevolutionary change does lead to the creation of new species, however. The process of speciation begins with one species, and through microevolutionary mechanisms, creates two distinct species. These species then take on their own independent fates, and can become subjects for the study of macroevolution.

I'd like to offer what I hope is a compelling "proof" (and I use the word with reluctance, since it will be shoddy at best; I'm neither a biologist nor a logician) that microevolution cannot actually create new species.  I don't have much to say about the science involved because I lack authoritative scientific knowledge, but I can offer a (quasi) logical proof based on the mechanics of the question.  Ok, ok, it's not really a proof.  But it has symbols, so it must be right.  Right?

Definitions:

1. Microevolution: evolutionary change within a species.
2. Macroevolution: evolutionary change that results in speciation; the change of one species into another.
3. Species: two organisms are of the same species if, by mating, they can produce fertile offspring.

let:

1. A be the original species.
2. A^n be a permutation of A obtained by microevolution.
3. B be a second species that evolved from A.
4. m() be the process of change within a species (microevolution).
5. M() be the process of speciation (macroevolution).

   m() and M() accept as arguments any species name (that is: A, A^n, B, etc).

The process of microevolution can only result in changes within a species.  Therefore, for all m(A), the result can only be a permutation of A, A^n.  m(A) can never result in a species B, because m() cannot cause a change in species.

So, looking at the spectrum of organisms as species A evolves to species B, we could see many permutations of A caused by m(), but if m() is the only mechanism changing the original species, we will never see a B.  In order for B to be produced, there must be exist some mechanism M() capable of causing speciation.

This of course assumes that change happens along a continuum like

A --> A^x --> A^(x+1) --> A^(x+2) --> ... -> A^(x+n) --> B

and it's that last step in the chain from A^(x+n) --> B that microevolution by definition cannot accomplish.  There must be some process M() if B is to evolve from A or some permutation of A.

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If any of the numerous noders with more expertise/ability/experience in logic and biology find problems in the above writeup, please /msg me.  I like eating my words.  They're tasty.

Pursuant to that: several nice people have informed me that the reason this "proof" (and I agree with their scare quotes) is shoddy is that the aim of the proof is already contained within the definitions.  They're right, of course, but I'd like to stress that the definition of microevolution above is not mine. The Other Dan offers the accepted scientific definition of microevolution: "a small change within a species" but goes on to say that "[m]icroevolutionary change does lead to the creation of new species."  All my "proof" is attempting to do is show that these points are irreconcilable.

Microevolution is a somewhat general term used to describe evolutionary changes that occur on:

1. a molecular level (changes within DNA, i.e. mutations)
2. an individual organism level (DNA recombination, chromosomal mutations, reproduction, natural selection, etc.); or
3. a population level (genetic drifts, phyletic shifts, founder effects, etc.)

Compare with macroevolution.

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From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.