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Author Topic:   MACROevolution vs MICROevolution - what is it?
RAZD
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Message 1 of 893 (385009)
02-13-2007 9:07 PM


This is the essence of the debate isn't it?

In several recent posts there have been the usual references to "macro"evolution and "micro"evolution:

EpicThought in Message 9

While I personally believe that evolution should be taught in schools (along with ID) I don't believe in any theory I have seen on macro evolution.


nemesis_juggernaut in Message 17
I believe there is a limit on the speed of beneficial evolution that hits a wall, which thus, would render evolution on a macro scale impossible.

Oliver in Message 196
The way I see it is that the whole of nature disproves macro-evolution but not micro-evolution. We simply cannot directly observe macro-evolution and if someone could provide an example I would greatly appreciate it.

where I have responded each time with a rather simple request:

Please define "macro"evolution - so we can be sure we are (a) talking about evolution and (b) we are talking about the same thing.

Also define "micro"evolution just to be sure we are talking about something different.

It should be easy eh?.

I think this and the current responses should be discussed in a new thread because it is fairly central to the whole debate and to keep other threads from going off-topic.

Response from EpicThought in Message 14

Please define "macro"evolution

evolution at the species level or above

Also define "micro"evolution"

evolution belowe the species level

Response from nemesis_juggernaut -- none to date.

Response from Oliver in Message 198

Micro, as in variation and adaptation.
Macro, as in complete change fronm one creature into another.
Thanks..

My response to Oliver is in Message 200, where I asked for further clarification of what were the limits on each "type" of evolution. The critical elements of the reply are:

Micro, as in variation and adaptation.

Do you mean all mechanisms of evolution that have been observed in the process of change in phenotype and genotype of a species population up to and including what is called "speciation" - using a standard biological species definition of non-breeding populations as a definition of species?
Macro, as in complete change fronm one creature into another.

How much change and in what time-frame?

In one sense this occurs at the moment of speciation: one species has become another. They no longer interbreed because they are different.

Or do you need the accumulated change from, say, two speciation events, to show that change is continuous and necessarily divergent rather than convergent? That second generation daughter (grand-daughter) species are more different from the original parent species than the intermediate ones?

... there's more to it, and so far there has been no response.

I will be moving my reply to EpicThought here to keep it out of the {Why should ID be taught in science classes...} topic discussion:

To EpicThought Message 14:

So when speciation has occurred it is due to "micro"evolution, and when that new species continues to evolve it is due to "macro"evolution?

That isn't saying much, nor is it any kind of problem for evolution and it matches the evidence we have already of continued evidence of evolution after speciation.

In essence once a second speciation has occurred then de facto "macro" evolution has been observed to occur.

We can look at the fossil evidence of foraminifa for instance:
http://www.don-lindsay-archive.org/...on/foram_article3.html

quote:
Drs. Tony Arnold (Ph.D., Harvard) and Bill Parker (Ph.D., Chicago) are the developers of what reportedly is the largest, most complete set of data ever compiled on the evolutionary history of an organism. The two scientists have painstakingly pieced together a virtually unbroken fossil record that shows in stunning detail how a single-celled marine organism has evolved during the past 66 million years. Apparently, it's the only fossil record known to science that has no obvious gaps -- no "missing links."

"We've literally seen hundreds of speciation events," Arnold added. "This allows us to check for patterns, to determine what exactly is going on. We can quickly tell whether something is a recurring phenomenon -- a pattern -- or whether it's just an anomaly.


Thus we have observed "macro"evolution.

This also means that no other mechanism is needed for "macro"evolution to occur than is needed for "micro"evolution -- the continued evolution within each differentiated species -- and thus there is no barrier to "macro"evolution to continue to happen and increase the differentiation between the species as time passes.

This also matches what we see in the fossil record.


(note to admins & others: The above reply will be deleted from the ID thread when this topic is promoted).

This is the essence of the debate: when does change become sufficient to be "macro"evolution and how does it occur.

What is the difference between "genus" "family" "order" and all those other taxonomic classifications? When does one become the next level? What is the change that is involved?

Enjoy.

Edited by RAZD, : updated sig


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AdminNosy
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Message 2 of 893 (385022)
02-13-2007 10:11 PM


Thread moved here from the Proposed New Topics forum.
  
subbie
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Posts: 3508
Joined: 02-26-2006


Message 3 of 893 (385028)
02-13-2007 10:28 PM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


The answer to this question is the same as the answer to the question, "What does 'kind' mean?"

In other words, the answer is, "Whatever we need it to be so that we can cling to the meaningless distinction between 'micro' and 'macro.'"


Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin

We see monsters where science shows us windmills. -- Phat


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mick
Member (Idle past 2517 days)
Posts: 913
Joined: 02-17-2005


Message 4 of 893 (385039)
02-13-2007 11:45 PM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


First, there seems to be a taxonomic usage of the term "macroevolution". Opponents of evolution are often using the term as a proxy for folk taxonomy. Dogs, cats, spiders, ants, birds, snakes, human beings, monkeys, flowers, etc. are all taken to be macroevolutionary units because they all correspond to an uninformed folk taxonomy that we learned as children.

You often hear them say things like "nobody has ever seen a dog evolve into a cat" or whatnot, in which case macroevolution is presumably equivalent to the diversification of new Linnean families; but when talking about less familiar groups of animals, I have often heard things like "yes but it's still an insect isn't it?", in which case macroevolution is taken to be equivalent the diversification of a Linnean class! On the other hand, talk of human evolution will resound with "the missing links between Australopithecus and Homo", so in this case macroevolution is the diversification of a genus.

I'm afraid there's no sense to any of it, because it's taxonomy by people who aren't sufficiently motivated to inform themselves about classification. Hence we hear both "it might have microevolved, but it's still a monkey" and "it might have microevolved, but it's still unicellular" in the same breath!

An alternative usage is in terms of biological structures. Microevolution is taken to be molecular evolution and the evolution of proteins, while macroevolution is taken to be the evolution of body parts (especially tissues and organs) or body plans. So we often get "how does evolution create hair/wings/hearts/brains/eyes/larvae/sexes" etc. The distinction probably has more merit here; I can appreciate there may be a conceptual difference between "tweaking" an existing metabolic pathway and evolving a new limb. In general it boils down to the idea that microevolution is the modification of a single modular trait, while macroevolution is the coordinated evolution of multiple traits or the origin of new "modules" which change the systematic functioning of the organism. So, the evolution of the ability to hold breath for a long time is microevolution, the evolution of a hand into a flipper is microevolution, the evolution of specialised hemoglobin is microevolution, but the evolution of an aquatic lifestyle from a terrestrial ancestor is "macroevolution" and impossible.

Finally, they often just mean "microevolution can be observed in a lab experiment, while macroevolution cannot". So microevolution can be observed in real-time and in living organisms, while macroevolution must be inferred (for example from fossils, systematics, or whatever). The attack on evolution then amounts to an attack on the validity of scientific inference.

Mick


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Doddy
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Posts: 563
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Joined: 01-04-2007


Message 5 of 893 (385050)
02-14-2007 12:19 AM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


I suggest you read what CreationWiki has to say on the issue. It's a source edited by all sorts of creationists, outside of any specific debate, so should give a nice definition. They even have pictures.

http://creationwiki.org/Macroevolution

The definitions they use are

  • Macroevolution - long-term evolution that results in the formation of new taxonomic groups
  • Microevolution - the small scale change in organisms within the same species, which can lead to a subspecies or variations of the same created kind.

Then again, the EvoWiki has this to say about it: http://wiki.cotch.net/index.php/Macroevolution

quote:
Creationists accept microevolution, which they define as evolution within kinds (kinds meaning sometimes species, sometimes bigger taxa, depending on taste) but deny that a kinds may evolve into another (macroevolution). This argument is strongly opposed by scientists because microevolution and macroevolution are the same process in different scales and it is irrational to say that only one of them exists.


"Der Mensch kann was er will; er kann aber nicht wollen was er will." (Man can do what he wills but he cannot will what he wills.) - Arthur Schopenhauer

Help inform the masses - contribute to the EvoWiki today!

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PaulK
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Message 6 of 893 (385078)
02-14-2007 2:20 AM
Reply to: Message 4 by mick
02-13-2007 11:45 PM


A dog giving birth to a cat would be creating a new Linnean Family by saltation. In direct cotnradiction to evolutionary theory. If that is the creationist idea of macroevolution then it doesn't happen. Everything from the first life to the array of species currecntly inhabiting the planet is microevolution.

Likewise the only definition of "kind" that creationists have presumes the absence of evolutionary links. Thus if macroevolution is between "kinds" all evolution is microevolution.

In the first case "macroevolution" is a strawman. In the second it has been something that cannot happen because the definition oxymoronic. And in both cases the argument fails because the creationists idea of "microevolution" covers ALL of evolution.


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Hawks
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Posts: 41
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Message 7 of 893 (385089)
02-14-2007 2:53 AM


Macro vs micro
While trying to get the folks at overwhelmingevidence to define what they meant by increases in information and function, someone made the claim that macroevolution needs increases in both, whereas microevolution needs neither. That sure cleared things up.

Edited by Hawks, : *Edited to change either to neither.


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cavediver
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Message 8 of 893 (385109)
02-14-2007 7:49 AM
Reply to: Message 7 by Hawks
02-14-2007 2:53 AM


Re: Macro vs micro
That sure cleared things up

:laugh: ROFLMAO :laugh:

I'm feeling very delicate and pathetic with flu (i.e. nasty cold and chest cough) but you made my day with that :D


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Taz
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Posts: 5069
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Message 9 of 893 (385161)
02-14-2007 12:51 PM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


I am speaking as a layman who knows biology on a general level. The way I understand it, the term microevolution refers to small changes in allele frequency due to mutation and natural selection within a population. Macroevolution refers to a kazillion small changes over long periods of time giving rise to changes significant enough to be noticed.

I guess to me the two terms are analogous to walking. If I walk down the street, when does "micro"walking becomes "macro"walking? Do I have to walk to the store down the street for it to be macro? Do I have to walk to the next town for it to be macro? In other words, I see the two terms, macro and microevolution, as essentially referring to the same process, which is just small changes in the allele frequency.

Another analogy I could think of is the evolution of language. Exactly when and how did old english become modern english? Exactly when did certain aspects of latin break away and gave rise to the romance languages such as french, italian, and spanish?

So, when the creationist demand to see a transition that looks something like a creature with a dog's head, a cat's tail, a frog's legs, and a snake's scale, he's being unfair. It's unfair because that's not how evolution works, much the same way as that's not how evolution of language works. The small very gradual changes over long periods of time accumulated and gave rise to a whole new language.

We could also look at the evolution of technology and see essentially the same thing. Was there an exact year, month, day, hour, or second when the world decided to change from the stone age to the bronze age? Was there an exact year, month, day, hour, or second when the world all in one voice decided to change from the bronze age to the iron age? What sort of tool should be considered a transition between a bronze age tool and an iron age tool? Is a computer a modern or post modern machine?

Now, remember that I am a layman in terms of evolution. Corrections are welcome :)


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crashfrog
Inactive Member


Message 10 of 893 (385162)
02-14-2007 12:56 PM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


MACROevolution vs MICROevolution - what is it?

A smokescreen where any evidence offered to support evolution can be shunted into "microevolution" which, it is claimed, was never under contention in the first place.

And since the terms are perpetually undefined, it's remarkably easy to employ the smokescreen. Since "macroevolution" is never defined, it's impossible to objectively determine what evidence would be required to support it.


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macaroniandcheese 
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Message 11 of 893 (385165)
02-14-2007 1:11 PM
Reply to: Message 1 by RAZD
02-13-2007 9:07 PM


until they see a crocodile turn into or give birth to a dolphin (which is not proposed by any theory of evolution, except the misdefined idea creationists have of evolution) they will not believe in evolution.
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Taz
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Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 12 of 893 (385169)
02-14-2007 1:21 PM
Reply to: Message 10 by crashfrog
02-14-2007 12:56 PM


crashfrog writes:

And since the terms are perpetually undefined, it's remarkably easy to employ the smokescreen. Since "macroevolution" is never defined, it's impossible to objectively determine what evidence would be required to support it.


Actually, a creationist I talked to once told me how I could convince him "macro"evolution is real. All I have to do is show him a cat giving birth to a dog or a fish growing 4 legs and turn into an iguana. I think that's pretty much what creationists think "macro"evolution is.
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Fosdick 
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Message 13 of 893 (385194)
02-14-2007 2:52 PM
Reply to: Message 10 by crashfrog
02-14-2007 12:56 PM


Macroevolution vs. Microevolution
crashfrog wrote:

A smokescreen where any evidence offered to support evolution can be shunted into "microevolution" which, it is claimed, was never under contention in the first place.

And since the terms are perpetually undefined, it's remarkably easy to employ the smokescreen. Since "macroevolution" is never defined, it's impossible to objectively determine what evidence would be required to support 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:

quote:
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.)

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:

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

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

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


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:

quote:
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...
And he presents a three-page table that extensively differentiates the "organismal level" form the "species level."

Hope this helps.

—Hoot Mon


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RAZD
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Member Rating: 3.7


Message 14 of 893 (385345)
02-15-2007 8:27 AM
Reply to: Message 4 by mick
02-13-2007 11:45 PM


No YEC's YET?
First, there seems to be a taxonomic usage of the term "macroevolution". Opponents of evolution are often using the term as a proxy for folk taxonomy. Dogs, cats, spiders, ants, birds, snakes, human beings, monkeys, flowers, etc. are all taken to be macroevolutionary units because they all correspond to an uninformed folk taxonomy that we learned as children.

I think this covers the problem best. What we see are the results of long term evolution, where it is convenient to break things into similar groups of animals, but that the patterns for what we see being caused by common ancestors is not so apparent.

You often hear them say things like "nobody has ever seen a dog evolve into a cat" or whatnot, in which case macroevolution is presumably equivalent to the diversification of new Linnean families;

It's like they expect a new branch of a tree to appear suddenly and full grown, with leaves and twigs.

An alternative usage is in terms of biological structures. Microevolution is taken to be molecular evolution and the evolution of proteins, while macroevolution is taken to be the evolution of body parts (especially tissues and organs) or body plans. So we often get "how does evolution create hair/wings/hearts/brains/eyes/larvae/sexes" etc. ... In general it boils down to the idea that microevolution is the modification of a single modular trait, while macroevolution is the coordinated evolution of multiple traits or the origin of new "modules" which change the systematic functioning of the organism.

That is rather reducing micro to a minimum effect and pushing macro to a maximum effect, when in fact there is a spectrum in between.

The real question it seems to me is when do two recently diverged species descendants become sufficiently distinctive that "macro"evolution has occurred: what is the minimal requirement?

I had proposed this to be a question for YEC's to answer, and have not seen one yet.

Thanks to the others for their responses as well. I don't think there is much "controversy" on the evolution side.


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RAZD
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From: the other end of the sidewalk
Joined: 03-14-2004
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Message 15 of 893 (385420)
02-15-2007 4:11 PM


The place of SPECIATION in MACROevolution
This is the generally accepted dividing line (currently) between "macro"evolution and "micro"evolution, in both biology and creationism.

In biology the process of "micro"evolution is mutation, genetic drift, etc, causing variation within the gene pool, and then selection by survival and breeding to pass genes on to the next generation, or natural selection of "more fit" individuals over "less fit" individuals for the particular {environmental\inner-population} dynamics that prevail.

In creationism this is often referred to as "variation and adaptation" but is the exact same mechanism, just using a different {words\names} to say the same thing (possibly to hand wave away any implication that we are really discussing "evolution").

In biology the process of "macro"evolution is the accumulation of differences between populations that have become dis-linked after speciation has occurred: the more time that passes the greater the likelihood that differences will be noticeable as being significant.

In creationism there is often a "cognitive dissonance" issue regarding what evolution actually says happens and a common belief that something else happens on a comparatively brief time-scale and that causes some kind of sudden significant change.

The point of this topic is to dissect this common - and erroneous - belief and show how it is false.

There are several definitions of "species" that make this "dividing line" a little muddy.

Most of the muddiness involves asexual species, species that reproduce only by cell division. In essence each individual is a sub-population that does not interact genetically with the other sub-populations (except by horizontal gene transfer, which is not necessarily species inter-specific either). Thus in asexual species the definition is fairly arbitrary: they are classed into species by the degree of similarity within groups. This is similar to the classification of species into higher taxons in traditional taxonomy.

The real issue for "macro"evolution with creationists involves sexual species, so the species definition for asexual species is not that big an issue. For sexual species it is fairly well accepted that the failure to breed between two populations is sufficient evidence of speciation -- whether the two population can breed and produce viable hybrids is not considered relevant when the two populations by behavior don't breed.

We can use ring species, such as the Asian Greenish Warblers (Phylloscopus trochiloides) to demonstrate that it doesn't take much difference to create a behavior barrier to mating:

quote:
In central Siberia, two distinct forms of greenish warbler coexist without interbreeding, and therefore these forms can be considered distinct species. The two forms are connected by a long chain of populations encircling the Tibetan Plateau to the south, and traits change gradually through this ring of populations. There is no place where there is an obvious species boundary along the southern side of the ring. Hence the two distinct 'species' in Siberia are apparently connected by gene flow.

West Siberian greenish warblers (P. t. viridanus) and east Siberian greenish warblers (P. t. plumbeitarsus) differ subtly in their plumage patterns, most notably in their wing bars, which are used in communication. While viridanus has a single wing bar, plumbeitarsus has two. Around the southern side of the ring, plumage patterns change gradually.

Male greenish warblers are very active singers, using song both to attract females and to defend their territories. Each male has a repertoire of song units, and songs are made by stringing together units in various ways. There is much geographical variation in both the song units and the rules by which units are assembled into songs.

There is a clear gradient in song characteristics around the ring, with the northern forms viridanus and plumbeitarsus differing dramatically in their songs.



A modest change in plumage and mating song and there is no breeding behavior between the two populations. Remove the intermediate varieties and speciation has occurred. To visualize speciation occurring in time rather than space all one needs to do is consider the intermediate varieties to be ancestral rather than geographically removed.

One wing bar to two is not a significant change, but it is a change in a feature visible on the two different varieties. Change in mating behavior - song patterns - is a little different: it would not be something that would be recorded in any preserved specimens, but it is a distinctive part of mating behavior for all sexual species.

We can also look at the fossil record to see if there is a similar pattern with such ancestral rather than geographic separations. One such example is Pelycodus:

quote:

Click to enlarge

The numbers down the left hand side indicate the depth (in feet) at which each group of fossils was found. As is usual in geology, the diagram gives the data for the deepest (oldest) fossils at the bottom, and the upper (youngest) fossils at the top. The diagram covers about five million years.

The numbers across the bottom are a measure of body size. Each horizontal line shows the range of sizes that were found at that depth. The dark part of each line shows the average value, and the standard deviation around the average.

The dashed lines show the overall trend. The species at the bottom is Pelycodus ralstoni, but at the top we find two species, Notharctus nunienus and Notharctus venticolus.


What we see is a gradual trend towards increase in size with time (what has been called "Cope's Rule" as hypothesized by Edward Drinker Cope, who also first identified Pelycodus jarrovii in 1874, the "type" species of the adapid genus Pelycodus), until a branching point is reached at which time one population rapidly (by comparison - still over a period of many thousands of years) decreases in size.

The distinction of species from Pelycodus ralstoni to Pelycodus trigonodus to Pelycodus jarrovii can be considered fairly arbitrary: we don't know whether they could interbreed or not, and the classifications are based on small changes in skeletal structures and size.

Likewise the distinctions between Pelycodus jarrovii and Notharctus nunienus or between Pelycodus jarrovii and Notharctus venticolus could be considered arbitrary (especially in the absence of the other), but the distinction between Notharctus nunienus and Notharctus venticolus is not arbitrary: there is a clear division between the two populations with no overlap in sizes. Whether they could interbreed or not is not an issue - they were reproductively isolated by the time the top of this diagram is reached. Thus we see the same pattern in ancestral species resulting in non-breeding subpopulations as we saw with the ring species warblers.

Pelycodus is tantalizing here, because the above article goes on to say:

quote:
The two species later became even more distinct, and the descendants of nunienus are now labeled as genus Smilodectes instead of genus Notharctus.

Where 'genus' is the next level up from 'species' in the standard taxonomy and thus we have a pending "macro"evolution division of species into two different genus taxons. The point made is that it doesn't happen when the speciation event happens, but is a later accumulation of differences between the two daughter populations that are classified into two different genus groups.

Generally a 'higher' taxon group includes several co-existing species, all descended from an ancestral species (such as either Notharctus nunienus or Notharctus venticolus here) after a speciation event. Thus "macro"evolution starts with speciation but is only classified as "macro" (it never really "ends") after several more speciation events have occurred and where the difference is noticeable enough to justify an additional classification.

One could say that the mechanism for "macro"evolution is speciation, but there is nothing special about higher classifications other than that they are convenient for discussing the relative relations of various species. In this sense "macro"evolution is nothing more than an arbitrary convenience for biologists to classify species and is not really different from "micro"evolution.

This can be simplified as a series of non-arbitrary speciation events: we can have a species {A} that divides into two non-breeding daughter populations, species {B} and species {C}. Both {B} and {C} will continue to be {A} descendants ("dogs will always be dogs"), but equally {B} will not be {C} (dogs are not foxes, but both are canines). At this point {B} and {C} would still be in 'genus' {A}.

Further non-arbitrary speciation events would divide {B} into {D} and {E} and {C} into {F} and {G}, where now they would all be the same 'family' {A}, but {D} and {E} would be in 'genus' {B} while {F} and {G} would be in 'genus' {C}.

There would be more difference between {{D} or {E}} and {{F} or {G}} than between {D} and {E} or between {F} and {G} due to greater divergence of each species since the common ancestral species.

The only difference between evolution before speciation and after speciation, is the loss of gene flow once speciation has occurred, and the different population dynamics between formerly cooperating populations that are now in competition for the same resources. This change in population dynamics will drive an increased rate of divergence between the two populations, as selection will be for divergence away from each other rather than towards common ground -- or one will out-compete the other (ie - leads to extinction).

This change in dynamics may be one reason for the appearance of "punctuated equilibrium" (punk eek) in some fossil records. In fact one interpretation for Pelycodus evolution involves punk eek (it also includes some additional species and uses an alternate name for Notharctus nunienus - Pelycodus frugiverous - and moves Pelycodus jarrovii higher on the diagram):
http://www.mun.ca/biology/scarr/Pelycodus_punctuated.htm

Note that this shows there is some disagreement on the exact evolution path that occurred in this lineage, but that both agree that non-arbitrary speciation occurred at the point where Notharctus nunienus (Pelycodus frugiverous) or Notharctus venticolus have diverged into non-breeding populations.

This does not affect the issue of "macro"evolution being an accumulation of changes due to "micro"evolution over a period that involves numerous speciation events.

Enjoy.


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