Definition of evolution and the distinction between micro/macro


(Matthew Pevarnik) #142

That’s a bit dramatic but okay. So are you saying that a macroevolutionary change would be the difference between a human being and some Cyanobacteria? And every other thing in between would be microevolution? Like a common ancestor of some primate lineage splitting to what led to modern humans and chimpanzees? That certainly is quite ‘micro’ if that’s how big ‘macro’ is.

What is more useful are discussing lets say cladograms/phylogenetic trees. Here is one for Felidae:

Note that each cluster/lineage would be somewhat similar to the outdated and fading out of use Linnaean taxonomy. And thus Futuyma’s definition for macroevolution would be saying here that the pantera lineage is different enough from the bay cat lineage to warrant being called macroevolution. That is extremely different from what the example you gave.


(Chris) #143

But then what about new features that involve loss or damage to existing genes? Such as blue eyes and adult lactose tolerance in humans, or black fur in desert mice.


(Chris) #144

I agree. A problem with his definition is how we measure functional information. He has proposed a method for proteins but there are other sorts of information as you’ve pointed out.

Perhaps in the end we might need to accept that micro and macroevolution are general qualitative terms rather than precise technical terms.

Straying slightly, Wikipedia says “Microevolution is the change in allele frequencies that occurs over time within a population.” But does that definition encompass everything that would be called microevolution? Perhaps it would be better to say;

A change in allele frequencies that occurs over time within a population is an example of microevolution.


(Chris) #145

Here’s another one.


(Chris) #146

It’s also interesting to look at the references, one of which is
Szostak JW: Functional information: Molecular messages. Nature. 2003, 423: 689-10.1038/423689a.

You will see that measuring the functional sequence complexity of proteins is not something Durston et al thought up themselves. I’m pretty sure Szostak is not in the ID camp.

I could only see the abstract so I can’t say whether your assessment is correct.


(Matthew Pevarnik) #147

Okay. So you accept at least this much of the Feliformia phylogentic tree (note I put an X where your Noah’s Ark ancestor would have to be which would have occurred approximately 16 million years ago):

The source paper for this would be:

The main challenge that anyone who believes in the special creation of species (or original ‘kinds’) is identifying what that original ‘kind’ actually is and establishing that it is NOT related to any other original kind. Papers like this one provide rigorous statistical analysis on such phylogenetic trees and do find very strong evidence of common descent going back much further than you are suggesting.

Let’s go back one branch from this ‘x’ and we find the group Prionodon. They look something like this (a linsang):

These guys are cute but yet would have a common ancestor with the original ‘kind’ that you suggested was on Noah’s ark and thus mean you have to add a branch to your phylogenetic tree. Would there be a way to test if they are related to the ‘cat kind?’ Yes-the same way that you could do a DNA test to establish some of your ancestry- and they pass very well, including having many cat like behaviors!

Next up would be a grouping that is the Viverridae, Hyaenidae, Eupleridae, and Herpestidae.

First up: Viverridae (who cannot be in the cat ‘kind’):
image

Here’s another one in that grouping (an African Genetta- can’t ‘macroevolution’ between this and felines that share a common ancestor with the branch leading to both modern felines and linsangs):
image

If we grant this much, we are well on our way to going back much further than some original ‘cat.’

Do you have a way to actually determine who is related to what and what are the actual limits of ‘microevolution?’ You have had multiple definitions so far where it was super far (molecules to mankind) which allows for microevolution to do far too much- and then macroevolution was proposed as Futuyma’s definition which would make panthers, tigers and other cats qualify for macroevolution. So then you changed it again to be somewhat equivalent to ‘family’ level in the Linnaean scheme. However, this also provides problematic because the variation within the ‘felid kind’ is more dramatic than the various between this grouping and sister groups!

There is a much easier solution here and I think it is not to force the Bible to teach the special creation of ‘kinds’ but realize that ‘kinds’ in their culture meant something very different not meant to give us any scientific knowledge.


(Lynn Munter) #148

Agree with your whole post—I’d just add here that it’s really not some strange foreign usage at all. If I told you ‘God made all sorts of animals,’ would you automatically assume it meant a finite number of unrelated “sorts” had to have been produced all at once by God, and that we should make this the basis of our study of biology?


#149

That’s my assessment as well. The division between micro and macro appears to be as subjective as the division between genera, families, and orders in taxonomy. Humans tend to have this psychological need to put things into black and white categories, even in cases when there is a obvious spectrum of white to gray to black.

As emphasized in earlier posts, there isn’t a one sentence definition that is ever going to completely describe evolution, be it micro or macro. However, we can still use definitions that explain most of it.

The definition you are using (change in alleles) is trying to convey the idea of mutations spreading through populations. This is the basic mechanism that adds up to macroevolution.

A good analogy might be how humans grow up and age. There is no obvious point where we stop being a child and become an adult. There is no single point where we go from being young to old, short to tall, or skinny to fat. It could also be said that growth and aging are not linear. When we go through puberty there are changes that happen quite quickly, and it is followed much slower changes in our bodies. We microgrow each day, and it accumulates into macrogrowth and macrochange over our lifetimes. That seems to be very similar to how evolution works.


#150

It is also a method they wouldn’t use since it requires common ancestry and conservation of sequence across very divergent species. In effect, it is measuring the functional information that evolution has created.


#151

I don’t know about blue eyes, but lactose tolerance and black fur in desert mice did not involve a loss or damage to existing genes. In the case of lactose tolerance there was a mutation which allowed expression of the lactase gene in adulthood. Those without the mutation shut down lactase expression after weening. In the case of mice with black fur, these are mutations in a cell receptor that allows production of melanin throughout hair production instead of just at the beginning. In both cases it is a change in gene expression that produces the phenotype. No genes are lost or damaged.


(Chris) #152

Normal is shown by other mammals and more than 50% of humans today. Lactase is produced in infancy to digest the mother’s milk and then shuts off after weaning. The defect fails to switch off lactase production. Yes it is damage to existing genes, in fact there are a few different mutations that accomplish this.
Similarly in the desert mice it is a defect in signalling between genes that is responsible for dark fur.
Blue eyes is a defect in the HERC2 gene which regulates the OCA2 gene.


#153

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?


(Stephen Matheson) #154

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.


(Chris) #155

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.


(Lynn Munter) #156

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?


(A.M. Wolfe) #157

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.


(A.M. Wolfe) #158

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).]


(Chris) #159

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


(A.M. Wolfe) #160

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.


(Chris) #161

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.