Why Is Only "Micro Evolution" Acceptable?

[madnak]

Wikipedia describes the difference between microevolution and macroevolution as one of approach, and I think that's a good way of looking at it. The terminology is used to describe general rules of thumb and broad categories. None of it is very technical. Neither is "species," for that matter.

Examples of similar sets of categories are the social sciences and the branches of philosophy. How do you distinguish psychology from sociology from anthropology from history? How do you distinguish ethics from epistemology from metaphysics from ontology? You don't.

The reason creationists love the distinction is that macroevolution deals with changes that happened millions or billions of years ago. As a result, it can never be complete or systematic - there's only so much we can learn about the distant past. And that makes macroevolution an easy target - speculation is called "bad science" and incomplete knowledge is characterized as "holes in the theory of evolution."

[vhawk01]

[ QUOTE ]
Also, to clarify,

[ QUOTE ]
3) The accepted meaning of 'macroevolution' is where a change in an animal's genetic makeup is made, but where that change does affect what species said animal can mate with.


[/ QUOTE ]

is incorrect, in my opinion, because when someone uses the term "macroevolution" they aren't talking about any one, specific, genetic change that alters the reproductive capabilities of an organism. Even microevolution can do this (not every individual has an equal chance of mating with another individual, even of the same species, for instance). When you talk of macroevolution, it typically involves many generations and a large shift in allele frequencies, not any "one" mutation that instantly makes one individual incapable of reproducing with others of his/her species.

[/ QUOTE ]

So macroevolution is just microevolution times X, where X is defined as "whatever number is big enough to invoke the argument from incredulity." I'm not trying to be snippy with you here, but you still aren't explaining to me what is the actual difference between the two things. Macro is more than micro, sure, ok, but how much more, and what is the fundamental difference between the two that leads to the idea that one is possible/has happened and the other hasn't? Its like saying sure, you picked one apple, but it is impossible to pick ten apples.

[vhawk01]

[ QUOTE ]
[ QUOTE ]
So the only ambiguity lies in what is considered 'species change'?

[/ QUOTE ]

I'm not sure what you mean. Species don't change from one to another. They diverge from one species to two distinct species. Could you clarify?

[/ QUOTE ]

Sure they do. Think of all species like ring species, because they are, temporally not spatially. The simplification of one species diverging into two is fine, but its a little misleading on this specific point. If it were somehow possible to take one group of, lets say salamanders, and keep them together without any outside influence, no emigration or immigration, but still a shifting environment and such, and isolate them for millions of years, what would we have? Would we have a new species? The individuals alive millions of years from now almost certainly could not reproduce with the current individuals, and if they could, change millions to tens of millions or hundreds of millions or whatever number is big enough. So are they the same species? Why not? There was no diverging, there was no split, one "species" morphed into a totally different species. Heck, they might even look just like birds if the selection pressures were correct and the timeline was long enough.

[vhawk01]

[ QUOTE ]
Wikipedia describes the difference between microevolution and macroevolution as one of approach, and I think that's a good way of looking at it. The terminology is used to describe general rules of thumb and broad categories. None of it is very technical. Neither is "species," for that matter.

Examples of similar sets of categories are the social sciences and the branches of philosophy. How do you distinguish psychology from sociology from anthropology from history? How do you distinguish ethics from epistemology from metaphysics from ontology? You don't.

The reason creationists love the distinction is that macroevolution deals with changes that happened millions or billions of years ago. As a result, it can never be complete or systematic - there's only so much we can learn about the distant past. And that makes macroevolution an easy target - speculation is called "bad science" and incomplete knowledge is characterized as "holes in the theory of evolution."

[/ QUOTE ]

And also, like I said right below this post, the argument from incredulity is one of the most powerful arguments, since we know that the less people know about something the more confident they are in their knowledge.

[Bill Haywood]

[ QUOTE ]
The ONLY non-arbitrary line between micro and macro is speciation.

[/ QUOTE ]

Honest to God? That doesn't seem right to me.

Say a single species is divided by a mountain range into two groups.

A brand new mutation occurs in one, say, the sickle cell trait, which I believe is only a single change in one base pair. This gives significant resistance to malaria, and spreads quickly.

To me, that is what macro evolution is -- the evolution of novel traits, as opposed to a change in how often an allele appears in a gene pool.

The sickle cell population remains able to mate with the other one, so macro evolution has occurred, but not speciation.

[Matt R.]

[ QUOTE ]
So macroevolution is just microevolution times X, where X is defined as "whatever number is big enough

[/ QUOTE ]

Not exactly. Macroevolution deals with evolution beyond individual species. We can take microevolution times X for X as big as we want, and it isn't sufficient to be in the domain of macroevolution (although it is necessary). The other definining criteria is that speciation has to occur. This is because macroevolution deals with topics like diversity of species (which, of course, speciation is necessary for). I think there may be other ways that people use the term macroevolution, but those seem to be confusing and incorrect.

[ QUOTE ]
Macro is more than micro, sure, ok, but how much more, and what is the fundamental difference between the two that leads to the idea that one is possible/has happened and the other hasn't?

[/ QUOTE ]

There is no fundamental difference between the two. I think the idea that one is impossible comes from a misunderstanding of evolution (albeit an extremely subtle misunderstanding of how speciation occurs). If we assume that microevolution occurs in a population, and that reproductive viability is dependent upon heritable characteristics (genes), then speciation is inevitable. Microevolution leads to macroevolution.

To easily see this, just split a population up into two groups. If there is no gene flow present between the two groups, then due to genetic drift they will diverge genetically over time (this process is random, or at least partly random). If we acknowledge that there are genes responsible for reproductive success, then these genes will diverge over time as well. Since there is no selective pressure for population 1 to be reproductively viable with population 2, over time they will no longer be reproductively viable with each other. This is simply due to random mutations in the genome, which we already acknowledged occurs (microevolution). These simple changes in allele frequency lead population 1 to differ from population 2, and the genes responsible for reproduction diverge via the same simple mechanism.

Of course once there are no remaining members that can interbreed, then over thousands and thousands of generations they continue to diverge (no gene flow). Give it long enough, and the two species look nothing alike. Now just repeat this process over and over again for millions of years, and you can see why we have so many species that look so vastly different.

[Matt R.]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
So the only ambiguity lies in what is considered 'species change'?

[/ QUOTE ]

I'm not sure what you mean. Species don't change from one to another. They diverge from one species to two distinct species. Could you clarify?

[/ QUOTE ]

Sure they do. Think of all species like ring species, because they are, temporally not spatially. The simplification of one species diverging into two is fine, but its a little misleading on this specific point. If it were somehow possible to take one group of, lets say salamanders, and keep them together without any outside influence, no emigration or immigration, but still a shifting environment and such, and isolate them for millions of years, what would we have? Would we have a new species? The individuals alive millions of years from now almost certainly could not reproduce with the current individuals, and if they could, change millions to tens of millions or hundreds of millions or whatever number is big enough. So are they the same species? Why not? There was no diverging, there was no split, one "species" morphed into a totally different species. Heck, they might even look just like birds if the selection pressures were correct and the timeline was long enough.

[/ QUOTE ]

I don't think it's very common to define species temporally. It's just not that useful. When we talk of a speciation event, it's one species diverging into two. There's really no mechanism where one species can become another single species, because in any successive generation they're going to be reproductively viable. Unless, as you said, we skip around in time, but since this can't occur it's kind of pointless to say one species morphs into another.

If we assume a continuous flow of time, the only way for speciation to occur is for one species to diverge into two. Of course one or both of the divergent species may closely resemble its ancestor (especially if the divergence was recent), but they can still be separate reproductively.

I think the gist of it is the commonly used definition of species loses all value if you start skipping around over large gaps of time. Like you said, if you do this (and apply the definition of species), humans now are not the same species as humans of a few ten thousand years ago. You need to keep the definition to one specific time, without mixing and matching species from time 1 and time 2 to "test" for reproductive viability.

[Mempho]

Evolution is not proven at all. It is highly likely to be a myth of epic proportions that has used circular logic to present it as fact.

[bluesbassman]

[ QUOTE ]
Evolution is not proven at all. It is highly likely to be a myth of epic proportions that has used circular logic to present it as fact.

[/ QUOTE ]

I honestly can't tell whether you are leveling. For your sake, I hope you are.

[Mempho]

[ QUOTE ]


I honestly can't tell whether you are leveling. For your sake, I hope you are.

[/ QUOTE ]

So, if everyone else believes it, it must be true? Galileo might beg to differ.

For my sake, I decided not to be spoon-fed and tried to investigate both sides of the story. I didn't say evolution was false but I did say that it is likely that it is a myth.