Doubting Didymus

I have started this thread to try and sort this out once and for all. Barely a day goes by without someone mentioning this term in this forum alone. In the global creation/evolution debate as a whole, it is probably almost as commonly used a word as "it", "but", and "stupid".

... But does anyone know what it means?

I used to think I did at one stage. Here, for example, I spoke of macroevolution:

This is PZ’s take on the matter:

Most of us here are familiar with the definition that RufusAtticus prefers:

When I asked him just today to expand on that final line, he supplied this elucidation:

If the different perspectives I have seen offered up by three of this forums own moderators isn’t confusing enough, here are some more:

Talkorigins has this FAQ about what macroevolution is. It starts well, with this opening paragraph:
Punctuated equilibrium, Phyletic gradualism, Species selection and species sorting are all listed as examples of macroevolution. However, after a look at the history of the terms, the FAQ concludes with this:
This appears to me at least to constitute a contradiction. I don’t see how punctuated equilibrium, a theory tied intimately to such broad fields as ecology and geography, can be said to be the result of the same processes as intra-species population genetics. If it is, what is the point of classifying it as distinctively ‘macro’?

Again at talkorigins, The famous “29+ evidences for macroevolution” FAQ contains another definition of the word in its introduction.

Here, it simply means common descent. Nothing more, nothing less. Perhaps it is a definition geared up to directly combat the creationist interpretation of the word, which is still more mutable itself. I have seen creationists define macroevolution as speciation, as common descent, as a crossing of the created kind barrier, as large-scale morphological change. There seem to be the ideas that the 29+ evidences FAQ is designed to deal with, but can macroevolution really be classified simply as ‘common descent’? If so, where does microevolution, something that no-one would claim is not involved in common descent, enter the picture?

Some more, subtly different definitions from popular general biology texts:
Here, macroevolution is framed not as a process or a theory, but as a fact: something to be accounted for by either microevolution or some other process.

This definition is the one that I most often return to.
In other words, macroevolution is practically everything in evolutionary biology that isn’t bounded in by a species barrier. Genetic drift: (the bottleneck effect, the founder effect) and natural selection: (gene flow, mutation) are possibly the only things excluded by this definition.
The main problem I have with the term ‘macroevolution’ is not with what it is, but with when it is used. As I have shown in this post, people of all walks of life are using this term for only one of its many meanings. When people mean anagenesis, they say ‘macroevolution’. When they mean cladogenesis, they say ‘macroevolution’. Common descent, paleontological patterns, origins of diversity, genesis of novel properties, are all specific aspects of the great evolutionary canopy, but all are frequently substituted for the single word ‘macroevolution’. It is my opinion that the worth of this term has been, and is being diminished by frantic overuse.






~~Damn it, capitalize my name right. Love, Rufus~~

RufusAtticus

The reason why "macroevolution" can wear so many (similar) hats is that the Modern Synthesis and the molecular genetics destroyed whatever distinctions people were proposing for microevolution and macroevolution in the early part of the 20th century. Thus it is a term that has essentially lost its purpose and often arrises when a scientist needs to distinguish between a process in populations and a process between populations. I feel that my usage stays true to the original usage of the word yet allows it to be used in modern biology with out the feeling of obsolescence.

Now in order to toot my own horn, I want to post a link to my one contribution to the TalkOrigins archive, which also happens to deal somewhat with this issue.

Genetic Barriers Don't Exist

MrDarwin

Almost without exception, creationists use "macroevolution" to mean large-scale change, e.g., the origins of phyla and classes. They view speciation as "microevolution", or "evolution within kind". Understanding these different usages is critical because otherwise we're just going to talk past each other.

Extinction is a major element usually left out of discussions of macroevolution and personally, I've come to view macroevolution as a process of extinction more than anything else. Small-scale extinctions (of populations or of species) eliminate populations or species that are intermediate in morphology and could otherwise interbreed. Large-scale extinctions (especially mass extinction like the K/T) eliminate many species at one time and even entire groups, which again tends to eliminate morphological intermediates (thus emphasizing differences between the surviving groups) but also provides opportunities for evolutionary radiations of the surviving species into new habitats and ecological niches.

One excellent example is the evolution of birds: had none survived the K/T extinction, we might regard their fossils as a group of somewhat odd dinosaurs (especially now that we have found so many intermediate dinosaur-like birds and bird-like dinosaurs). But as the only dinosaurian survivors of a major extinction event, and as just one or a very few species of one particular specialized group, they have undergone a wildly successful evolutionary radiation as a group very distinct from anything else that survived the same extinction event.

Peez

I believe that the various definitions presented are all essentially the same in concept. What is lacking is precision in distinguishing microevolution from macroevolution, which is hardly surprising since there are shades of grey. What is the difference between running a long race and running a short race? One can easily differentiate the two in concept, but it might be more difficult to find a precise definition that will allow us to know exactly when one has gone from jogging to sprinting.

The term would be useful, if for no other reason, just to refer to large-scale evolution (generally above the level of species, though this is an arbitrary line). It becomes more useful when we ask questions about how mechanisms may work differently (or perhaps there are distinct mechanisms) in the evolution of higher taxa.

Peez

MrDarwin

I think there may have been a different "mechanism" operating during the origin of the phyla in the sense that these were the first complex multicellular animals, evolving body plans from scratch in a world that had never before seen anything more complicated than a sponge or jellyfish. In other words, this is an event--like the origin of life itself--that can never be repeated in the history of life on earth. But the rest I am convinced is due entirely to quite ordinary evolutionary mechanisms, with the odd mass extinction event thrown in to liven things up. Radiation, extinction, radiation, extinction, radiation. The longer ago the extinction, the higher the taxonomic classification we assign the survivors to.

RBH

MrDarwin wroteIn a recent political effort to push ID/YEC into the local school district's science curriculum, a Ph.D. (math, and an OEC as far as I can tell) member of the school board who was being advised by a Ph.D. microbiologist (a YEC, ICR member, and DI 100 statement signer), used "macroevolution" to refer to everything at the speciation and above level, and included abiogenesis in the definition of macroevolution. (The move was to eliminate "macro" from middle school biology and teach only "micro" - antibiotic resistance being the prime example given. It failed.) The board member claimed that was the way "macroevolution" was defined in a "college-level biology text," but declined to identify the text when I asked.

RBH


P.S. Don't waste bandwidth telling me abiogenesis ain't part of ToE: I know that!

Peez

I agree, but there are those who debate about the relative importance of selection at different levels, for example.

Peez

Kevbo

"Macroevolution" is sort of like the creationist term, "kind:" it creates at least some type of vague image in a person's mind, but fails to nail down any specifics. Definitions can be arbitrarily defined and adhered to, just like any other word, but the inherent problem is that we're trying to create concrete distinctions in a continuous spectrum of evolution. The real macroscopic world of evolution just refuses to be defined in meaningful long-term quanta, even "species" cannot be a universal definition. For that matter, the boundary between "life" and "non-life" is a little blurry too. What's special about a certain group of chemicals that makes it "alive," and how can that definition be applied universally from mammals to viruses?

This makes a lot of sense if evolution occured, because it isn't a goal-oriented process catering to our understanding, it's simply "what happened." This creates problems with a worldview that requires clear boundaries and obvious distinctions between separately created organisms. It might be useful to point this out to creationists who insist on playing semantic games about "macroevolution" and "kinds."

Macroevolution can be a fine and useful term in the context of professional biology, but it's an obfuscator with a muddied history when it comes to debates with creationists. The most practical solution might be to request that creationists define exactly what they mean by "macroevolution" if they insist on using such terminology. Then, you can point out that definitions are ambiguous or that their definition has been satisfied by evolutionary theory.

Godot

To be honest, I had never known of any macro-micro distinction before coming to II; it was always simply the ToE. Because of the potential for confusion and obfuscation by others, I don't think it is a term whose use should be continued.
Dividing it up adds a level of complexity that will only be of use to those within the field.

Goober

As I understand it 'macroevolution' means the development, by evolution, of the large scale differences between species.

Macroevolution is simply due to the accumulation of may small changes caused by microevolution, which is why it is so hard to seperate from microevolution. It IS microevolution, accumulated.

Which is why I think the terms micro and macro evolution are unnecessary. There is only evolution, not two distinct types of evolution.