MACROevolution vs MICROevolution - what is it?

Yes, they do seem perpetually undefined. There may still be ambiguity in these distinctions. I've been confused about them. So, I dug up these distinctions from relevant literature.E. O. Wilson (in Sociobiology, 2000, pp. 588-89) defines microevolution and macroevolution this way:

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Microevolution”A small amount of evolutionary change, consisting of minor alterations in gene proportions, chromosome struucture, or chromosome numbers. (A larger amount of change would be referred to as macroevolution or simply as evolutin.)

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Steven M. Stanley (in Macroevolution/Pattern and Process, 1979, p. 183) sides with Gould and others that much of evolution is punctuated, and he offers this differentiation of mechanisms:

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Table 7-1. Mechanisms that produce macroevolutionary trends, in the punctuated scheme, and analogous mechanisms that produce microevolutionary trends.

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Macroevolution: 1) Phylogenetic drift, 2) Directed speciation, and 3) Species selection.

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Microevolution: 1) Genetic drift, 2) Mutation pressure, 3) Natural selection.

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Some of Stanley's concepts seem dated and contentious, however; R. Dawkins probably would dispute "species selection," for example.S. J. Gould (in The Structure of Evolutionary Theory (2002, pp. 716-19) has this to say:

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An extensive analogy”"the grand analogy," if you will...between organismal microevolution and speciational macroevolution provides a good tool for assessing the difference imposed by scaling among the levels. I present this grand analogy below...

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And he presents a three-page table that extensively differentiates the "organismal level" form the "species level."Hope this helps.”Hoot Mon

I find it interesting and revealing that two Harvard luminaries in evolutionary biology, Ernst Mayr and E. O. Wilson, do not specifically agree on how to define microevolution and macroevolution. E. Mayr defines these terms in his glossary of What Evolution Is (2001):

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Microevolution Evolution at or below the species level.

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Macroevolution Evolution above the species level; the evolution of higher taxa and the production of evolutionary novelties, such as new structures.

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E. O. Wilson defines these terms differently, combining them under one definition:

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Microevolution A small amount of evolutionary change, consisting of minor alterations in gene proportions, chromosome structure, or chromosome numbers (A large amount of change would be referred to as macroevolution or simply as evolution.)

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It will be difficult for evolutionary biologists to agree on one set of standard definitions for these terms, and others, too. So much of their reasoning comes pre-loaded with contextual biases that are nearly impossible to resolve. Contextual battles persist in other threads (e.g., Message 101 over these terms and the contexts in which they are used.I think it is good to have multiple opinions on these issues. But some posters here are so convinced in their contextual righteousness that they call other posters "stupid" for not agreeing with them. I have personal experience with this, concerning the definitions of evolutionary terms. What I should have done experimentally was to post Wilson's and Mayr's definitions of microevolution and mavcroevolution as my own, and then sit back and watch the dogs clamor at my "stupidity."”HM

Look carefully at those definitions in Message 23, Mayr has macroevolution occurring above the species level, while Wilson has it occurring at the species level. They also disagree on this: Mayr says microevolution can happen at the species level, while Wilson says the species level is where macroevolution occurs.”HM

I took this part of Wilson's definition”"A large amount of change would be referred to as macroevolution or simply as evolution"”to imply speciation. I beieve that's fair.”HM

Is there only one process? I can think of five know processes that can provoke an evolutionary event, or a divergence, or at least disturb a population's Hardy-Weinberg equilibrium. Knowing for sure at which levels they operate could be helpful.”HM

Returning to Message 23, here's what I said: I made that conclusion based on my understanding that Wilson implies "speciation" in the word "evolution." If he doesn't imply that then I am wrong. So I took his definitions to mean: 1) microevolution implies subspeciation, while 2) macroevolution (i.e., evolution) implies speciation.Wilson defines "speciation" as:

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The process of genetic diversification of populations and the multiplication of species.

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And he defines "evolution" as:

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Any gradual change. Organic evolution, often referred to as evolution for short, is any genetic change in organisms from generation to generation, or more strictly, a change in gene frequecies within populations from generation to generation.

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I see ambiguity here, enough so as to question my own conclusion in Message 25. From where I stand on this, I think "microevolution" can happen without speciation, but "macroevolution" (or just "evolution") entails speciation. What do you think?”HM

Hi RAZD,I take notice in your Message 18”where you make a very nice study of “microevolution” vs. “macroevolution””that both terms waffle like Philadelphia lawyers around the concept of “speciation.” I think this is a measure of our general confusion. We have no consolidated and agreed-upon set of definitions. We’re drowning in a sea of ambiguities.”HMEdited by Hoot Mon, : punctuation