Definition of evolution and the distinction between micro/macro

How is it “damage”? Could I classify the allele that causes lactase production to shut down the damaged allele?

Why are you classifying this as a defect? Why isn’t the defect the allele where melanin production shuts down earlier?

This is inaccurate in at least 2 ways.

“The defect fails to switch off” is a mischaracterization of what we know. There is no “defect” in any biological sense of the term. The mutations (variants) that we know of (and there are likely others that we don’t know of yet) lie outside the lactase gene, in a control region. The most famous of these mutations is a gain of function: the promoter is more active with the mutation than without. (See this abstract or any review of the topic.)

So: at least for the most well-understood mutation, it’s not in a gene and it’s an increase in function.

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I don’t know where that article got it’s picture of the dog kind from but it’s not like the one at the Ark Encounter which looks like a nondescript mongrel. Hence I suspect that all the others are similarly false.

Footnote to the article:

Casual readers may not immediately recognize that the eight ancestral species I included above represent actual genera, not mere artistic representations of imagined “missing links”. They are, starting at the top and moving clockwise: Protictitherium, Ictitherium,E. ekakeran, C. spelea, Simocyon, Amphicyon, H. gregarius, and Proailurus. The last two, H. gregarius and Proailurus, have been specifically identified by Answers in Genesis as the probable Ark ancestors of canines and felines respectively; the rest are extinct members of their respective clades. Because creationists don’t dispute that these species existed, the Ark Encounter has to put them somewhere, and they would best fit within baraminology at or near the apex point of their clades.

It’s entirely possible that AiG picked something else for their display or just made it look different, I wouldn’t know.

ETA: @aarceng, there are really a lot of extinct members of Canidae. Do you have any idea which one the Ark Encounter thinks is their ‘original,’ and if you think the picture is ‘false,’ i.e. not really related to living canids, which of the other extinct Canidae would you classify that way, and what do you think they’re actually related to, if anything?

Can we all just take a moment and give thanks for the amazing beauty of modern visualization tools in the scientific literature?

That graphic is gorgeous. And so chock-full of information. I’m in awe.

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Sheep actually make for a really very interesting case study, since you mention it.

Have you ever looked at a family tree of the clade Bovidae?


(Source: Wikipedia.)

In English, we consider sheep and goats as quite distinct from cows! But there are places you can go in the world where the cows are quite small and the sheep are quite large, and the sheep’s neck is even generally in a straight line with his spine, and you look at them and say, “Wow, you know, cows and sheep really do look quite similar.” In fact, the entire Bovidae family tree looks quite similar, and it’s not hard for me to imagine them all diverging from a common ancestor over the past 20 million years, as asserted by evolutionary theory. So… was this micro- or macro-evolution?

For comparison’s sake: In one language in sub-Saharan Africa, there is no one catch term for hyenas. The word for spotted hyena is îgr̰im or dondo (depending on the dialect) and the word for striped hyena is doro or daro (depending on the dialect).

hyenidae
(Source: Wikipedia.)

The hyena family also originated about 20 million years ago and has also diverged, but in English we call them all (except the aardwolf) “hyenas” and most of us Anglophones would have no problem saying that they’re basically the same “kind,” if you want to go the baraminology route.

Does what we consider microevolution versus macroevolution depend on our cultural baggage? Or can we honestly say that we know a “kind” when you see one? Can you really not imagine, over 20 million years — that’s about 10,000,000 generations, give or take — that a sheep could become a goat or a cow or an antelope?

[Edit… Having now read the rest of the thread, I see that most of these points have already been made, and Chris has admitted that the line between micro- and macro- is somewhat fuzzy. But I’ll leave my post up anyway in case it’s of interest to anyone (and because I spent a lot of time on it, haha).]

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Have we found a workable definition for [the Neo-Darwinian Theory of] evolution?
Have we finished considering the distinction between micro and macroevolution?

I’m coming very late to the conversation, and I haven’t read every post in depth, but it seems to me that if you’re saying this —

— then I would dare say the two sides of the conversation have found some important common ground.

At the same time, if you’re still saying that “microevolution” is possible while “macroevolution” is not, then don’t we need to have a more precise technical understanding of which is which? (Note that I put the two terms in quotation marks because I’m using them in the sense that baraminologists use them rather than in the sense that consensus biologists do.)

My understanding is that having a porous boundary between micro- and macro- is just fine for consensus biologists because it is predicted by that paradigm, whereas it’s not at all predicted by any of the YEC approaches.

This is an honest question, not a zinger. I’d be interested to hear your response.

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Actually I don’t know how baraminologists use them. I’d like to see how consensus biologists use the terms. I have found a variety of definitions by biologists, such as Futuyma’s, and I don’t think there is a consensus definition.

I don’t think I 've said that, but I have said that I don’t agree that micro will inevitably accumulate to produce macro, and thus I don’t agree that macro is just micro + time. I also don’t agree that they are the same thing at different scales.

I also don’t agree that speciation is macroevolution since it could be the result of many different causes. Speciation could be the result of either micro or macroevolution. We currently have species and genera that can interbreed so the criteria of reproductive isolation is not always used. Recently African elephants were declared to be two different species even though there are existing hybrid populations.

Also macroevolution could take place within a species without resulting in speciation. Some would say adult lactose tolerance is macro but it has not caused humans to split into separate species, and nor is it likely to.

Thank you for the helpful clarification of your position; I get the sense that it distills a lot of the previous conversation, some of which I had only skimmed.

I don’t understand how small changes over literally millions of generations — when I stop to think about what tens of millions of generations actually means — can’t add up to big changes. But if a small platoon of professional biologists hasn’t convinced you, I’m not sure what value I can add to the conversation. :slight_smile:

Peace to you.

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I think we found that different areas of biology are using the terms differently, and that the terms tend to be arbitrary and subjective. It’s a bit like the difference between young and old.

Could you give us examples of genetic differences between lineages that you think could not be bridged by known microevolutionary processes?

Then what do you think macroevolution is, and how do you quantify it?

I haven’t said they can’t, I said they don’t necessarily add up to big changes. Some small changes, such as the sheep colour example I used above, are simply not of a type that will produce macroevolution.

Take chloroquine resistance in malaria parasites for example. This requires 2 point mutations and possibly some other changes. Probably this required several steps. But it only provides a net benefit in the presence of chloroquine and is detrimental otherwise. We know this because it loses resistance if the drug is discontinued.

Even such a small change took trillions of bacteria decades to achieve.

Btw, I’m still waiting for you to give examples of how micro and macroevolution are used by consensus biologists.

This is a straw man. Is anyone arguing that small changes always add up to big changes? There have been lots of small changes in the evolution of the tuatara and the coelacanth, but they haven’t added up to big changes. Instead, these famous “living fossils” have retained their essential character for hundreds of millions of years.

When I said what I said earlier about “consensus biologists,” I was merely piggybacking off of the “micro = below species level, macro = above species level” working definition that several others (who, incidentally, are working “consensus biologists” themselves!) used above. I understand you’re not satisfied with this definition. But if you’re looking for someone to take a deep dive with you into the primary biology literature, you’ve got the wrong guy! :slight_smile:

Peace,
AMW

Browsing some definitions on line.

TalkOrigins provides the following definition;

In evolutionary biology today, macroevolution is used to refer to any evolutionary change at or above the level of species. It means at least the splitting of a species into two (speciation, or cladogenesis, from the Greek meaning “the origin of a branch”, see Fig. 1) or the change of a species over time into another (anagenetic speciation, not nowadays generally accepted [note 1]).

Contrast this to New World Encyclopedia.

Macroevolution refers to evolution that occurs above the level of species, such as the origin of new designs (feathers, vertebrates from invertebrates, jaws in fish), large scale events (extinction of dinosaurs), broad trends (increase in brain size in mammals), and major transitions (origin of higher-level phyla). This is one of two classes of evolutionary phenomena, the other being microevolution, which refers to events and processes at or below the level of species, such as changes of gene frequencies in a population and speciation phenomena.

At times, the concept of macroevolution has been defined as including evolutionary change at and above the level of species, and microevolution below the level of species. As the dividing point, the process of speciation may be viewed variously as the purview of either macroevolution or microevolution.

One advantage of defining macroevolution = speciation as TalkOrigins does is that if accepted. then any instance of speciation becomes proof that macroevolution happens. A disadvantage is that no change that does not result in speciation counts as macroevolution no matter how complex it is or whether or not it provides a new feature or function.

A problem is the fact that the definition of what constitutes a species is not consistently defined. Although the “biological species concept” is often mentioned it is not the only one used, as shown by the recent declaration that African elephants are two species even though there are existing hybrid populations.

By contrast Durston’s definition given above,

Macroevolution: genetic change that requires a statistically significant increase in functional information.

avoids tying macroevolution to speciation and would include changes within a species. However it has the problem of actually measuring functional information in a wide range of circumstances.

My opinion is that macroevolution could occur at any level and that speciation (however it is defined) could be the result of either microevolution or macroevolution.

By analogy could “Guernsey” be changed to “Literary” by microevolutionary changes? Certainly;
Guernsey, Luernsey, Liernsey, … , Literaey, Literary. 7 steps in all.

However can it be changed by Darwinian mechanisms; random changes and natural selection? At each step change a random letter to a different random letter, and it can only be retained if it is beneficial which in this case means it must form a new proper word. Even if it’s possible it will take much more that 7 steps.

But if you are claiming that genetic differences between lineages can be bridged by known microevolutionary processes then it is up to you to show that a viable path exists for random mutation and natural selection to follow and that it can be accomplished in the time available.

Plasmodium falciparum has a population of about 10^12 in one sick person, around 200 million people are infected each year, and the generation time is short. Even so it took about 40 years to develop resistance to Chloroquine, and it still hasn’t solved the sickle cell problem. How much time then would it take for a similar change in humans with a population of <10 billion and generation times of ~20 years?

Jean K. Lightner discusses this in “Mammalian Ark Kinds”.

Do you find this satisfactory?

There is considerable diversity in this family. Most people would tend to think of sheep and goats as distinct from cattle. For these reasons it was decided to split the family and consider the subfamily the level of the kind. This probably over-estimates the number of kinds since antelope are found in more than one subfamily, but it is the simplest way to split until more information becomes available.

Do we classify things based on what “most people would tend to think,” or based on evidence?

In a way, I appreciate that she is trying to create a “hybrid” (if you’ll forgive the pun) system that accepts just as much of the relevant science as she can, while staying true to her deeply-held beliefs. This is not an easy tightrope to walk.

At the same time, when I see the different attempts at baraminology, I have to wonder, who determines the gold standard? How do we know for sure what constituted a “kind”? Is it just something we’ll have to wait to learn when we get to heaven? Maybe we just have to content ourselves with that. Is it decided by some blend of what model seems most convincing to us and which creationist organization has the funding and reach necessary to project its version of baraminology to the furthest reaches of the creationist internet? This sounds like I’m mocking, but please believe I’m honestly curious, brother: How do we adjudicate which baraminologist is right?

First off, neutral changes and even slightly deleterious mutations can be kept in a population.

Second, the same question applies. Can you point to a genetic difference between lineages that could not be produced by these mechanisms? You are saying that microevolution can not accumulate into macroevolution, so where are the examples of differences that are known to be impossible for micro to produce macro?

The genetic differences between the human and chimp genomes is consistent with the mutation rate and the expected number of differences according to population genetics.

That would be an example of microevolution finding a solution. That would argue against your claims.

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