Does evolutionary theory provide any useful scientific benefit?


(George Brooks) #287

@johnZ

What?!? What exactly are you trying to formulate with this strange combination of sentences?!?

Perhaps you need to start from scratch?

a) Since individuals cannot CHANGE their DNA composition, it is impossible for individuals to evolve.

b) Gene pools are the only things that can evolve. ANY change in the gene pool is part of evolution… good, bad or sideways…

c) The very foundation of these changes is that they are gradual… even as they might suddenly disappear because the changes are lethal… or gradually permeate the entire population after several generations because they are successful or popular.

d) The term “species” is probably the least helpful of all the evolutionary terms we could use.

Remember one thing … BioLogos supporters share your belief in one important thing: that God participated in the formation of life on Earth.

You think he did it in 6 days and BioLogos supporters think God took millions of years. Virtually all of the natural sciences confirm that it took millions of years.


(sy_garte) #288

Have you people never heard of Pokemon?


#289

Benkirk’s and Chris_Falter’s courteous exchange is a good example of how careful dialogue leads to better wording and a better grasp of the topics. Even for those already familiar with the topic, these kinds of explanations are helpful in learning how to best convey the details of evolution.

If we could somehow endow these two facts to the evolution-denial community, we would see tremendous progress in the general public’s confusion over what evolution is and how it operates.

The comment about “good, bad, or sideways” reminds me of how many times I’ve dealt with evolution-denying people who take for granted the medieval concept of scala naturae (the Great Chain of Being.)


(Steve Schaffner) #290

Your premise there is actually not quite true. While we don’t normally talk about individuals evolving, populations of cells within individuals do evolve. This is obviously true of cells in the adaptive immune system, but is also be true of stem cell populations. Some of that involves deleterious mutations arising and then being weeded out by selection, but it includes positive selection for beneficial mutations. For example, mutations in a number of genes confer reproductive advantage on hematopoietic stem cells, leading to their clonal expansion. Such mutations are of course beneficial for the cells, not for the organism – they often lead to leukemia, in the case of hematopoietic stem cells.

The interesting case is spermatogonial stem cells, which can undergo similar clonal expansions and can also ultimately cause cancer. Since these are germ line cells, however, the mutations can be passed on to offspring, and thus become involved in the larger process of organismal evolution.


(Steve Schaffner) #291

Sorry, John, but when biologists use the term “evolution” to communicate ideas to other biologists, that’s the sense in which they use it – all the time. If, for example, you don’t think changes to the Ebola virus during the recent outbreak represent evolution, then the problem is simple: you’re wrong. “Evolution” is a technical term, and you have to understand the technical meaning if you want to follow the conversation.


(George Brooks) #292

@glipsnort

Of course you know that I can re-word my original post so that I am talking about the evolution of genetic change in an individual propagating throughout all the cells of the body - - rather than some populations of cells changing in response to specific events, right?

I don’t think we need to quibble about limited groups of “populations of cells WITHIN individuals” evolving.


#293

Agreed. There are far too many equivocation fallacies promulgated around the term evolution such that I would think we would want to do all we can to avoid any further confusion. Yes, the word evolution is a very old word in the English language which had multiple meanings long before Darwin and his theory came along. Accordingly, that is why we are so careful to speak of evolution being changes in allele frequencies in populations over time. While other kinds of changes in individual organisms can and do occur, to call them evolution is inviting confusion, even if non-scientists’ use of the word evolve can be justified on the basis of Webster’s dictionary. Selection new terminology to fit new phenomena makes life simpler for everybody, especially the science student memorizing the terms.

Unfortunately, there are many today who find it easier to declare the entire science academy wrong (and even “fraudulent”) rather than educate themselves in the basic science and get it right.


(Steve Schaffner) #294

I didn’t mean to suggest otherwise. I was pointing out that this issue, like many in biology, has nuances.

Sorry, guys, but this is neither quibbling nor equivocation. Populations of cells in an individual are evolving biological systems, and one powerful approach to dealing with them is use the concepts, the tools and the language of evolutionary biology. This application is hardly trivial, either, since its scope includes all forms of cancer. One of the grad students in our lab, for example, is currently applying tests for positive and purifying selection, tests that would make sense to any evolutionary biologist, to mutations in a range of human cancers in order to identify oncogenes and tumor suppressors. In fact, referring back to the subject of this thread, one of the useful scientific benefits of evolutionary theory is precisely that it gives a good conceptual framework for understanding cancer.


(Benjamin Kirk) #295

The problem is, without these silly straw men, evolution is pretty simple and obviously true.

Another one we shouldn’t forget is randomness and mutation. Darwinian evolution requires ZERO new mutations, just heritable variation (an observable fact) and variation in fertility (another observable fact).


(George Brooks) #296

@glipsnort,

What is your motivation for this line of discussion?

My concern is that these kinds of discussions can lead to even MORE confusion.

When we talk about gene pools EVOLVING … we know that specific cells (usually germ cells) of specific individuals are experiencing mutations. And it is passing these changes onto future generations that eventually leads to the speciation of evolution.

The processes you want to feature in this discussion are easy to see as part of this process… when looking at multiple generations.

What shall we call it when just a SINGLE individual experiences mutation? Or just a pocket of cells of a single individual experiences mutation?


#297

Yes. That would probably qualify as a must-have “c” in our list.

Of course, the evolution-deniers will say, “But that’s no evolution! That’s just adaptation and variation.” Face-palm.


(Benjamin Kirk) #298

[quote=“gbrooks9, post:296, topic:548”]
What is your motivation for this line of discussion?[/quote]
If I may speak for Steve, it’s accuracy.

Possibly, but I suggest that you resolve your own considerable confusion first.

Biologists don’t talk that way. Populations evolve, not “gene pools.”

George, you are utterly, spectacularly wrong on this. While all cells “experience” (a terrible word choice) mutations, NO NEW MUTATIONS ARE REQUIRED FOR EVOLUTION.

None.

Zip.

Nada.

Evolution is changes in allele frequencies over time. We simply don’t need any new alleles (caused by mutations) to get evolution, just heritable variation, which exists and can be objectively measured.

George, please try to understand this: new mutations contribute very little to the quantity of heritable variation (polymorphism) in a population. Before you criticize Steve, you need to get this very, very basic point. Put another way, if God stopped all mutations tomorrow, evolution would chug right along for a very long time.

[quote]And it is passing these changes onto future generations that eventually leads to the speciation of evolution.[/quote]I have no idea what you are saying here. I have never, ever heard the term “speciation of evolution.” Please use standard terms.

I think that you are completely missing Steve’s point, which is that evolution still only happens to populations–but those populations can be populations of organisms or populations of cells within an organism. The latter kind of real-time evolution is the basis for acquired immunity.

[quote]What shall we call it when just a SINGLE individual experiences mutation? Or just a pocket of cells of a single individual experiences mutation?
[/quote]I’d call it life. An average of 3 mutations occur every time a cell replicates its DNA and divides. What you don’t seem to understand is that the vast majority of them are of no evolutionary consequence.

George, can you come to grips with the basic point that selection acts primarily on existing variation and that new mutations contribute very little to this pool of variation, except in rare cases like inbred mice and the variation caused in the acquired immune response?


(Benjamin Kirk) #299

Which is why deniers need the straw men that JohnZ has asserted, but never explained, here.


(Benjamin Kirk) #300

And the immune response.


(George Brooks) #301

@Benkirk,

  1. You are going to “ding” me because I don’t use the term “Populations”?

  2. I did not intend to imply that evolution can only happen with any additional genetic mutations. I agree with you on that point. Evolution can happen even without new mutations… because evolution is about what happens to the POPULATION … not to individual offspring.

  3. But I think it’s pretty obvious that if a diverse population of, say, DOGS, reflects a 1 Percent incidence of, say, skin pigment of BLUE … the probabilities are low that the BLue Dogs will become a separate species if no further genetic changes are experienced.

Whales did not become whales because a 0.1% whale allele configuration was already present in the population… and it just became the dominant allele configuration without any additional genetic adjustments.


(Benjamin Kirk) #302

I have no idea what you mean by “whale allele configuration” nor “dominant allele configuration.” I know what “dominant allele” means, but adding “configuration” to it makes no sense. Do you have some aversion to using “allele frequency”?

We know that a lot of whale evolution (or design) involved duplication of relevant genes, eventually producing additional alleles, but much of the phenotypic difference can be explained by dosage.


(Steve Schaffner) #303

To explain what biologists include in “evolution”. There seems to be considerable confusion.

Clarity without accuracy isn’t really helpful.

I’ve already told you: we call it evolution. If it doesn’t involve germ-line cells, we call it “somatic evolution”.

Now, for many purposes we can ignore evolution of cells within an individual organism, and treat their genome as fixed. That’s fine if you’re only interested in the evolution of the species. But if you want to understand cancer, or the probability of having two children with the same genetic disease, or why mutation rates rise with paternal age, you can’t do that.


(George Brooks) #304

I would love to catch myself IN TIME in the future from the error that evolution definitionally requires mutation. Could you tell me which sentence is most egregious in this regard? As soon as you stated your charge in a way that broke through my “veil of conscious perspective” I knew I could not intentionally mean that.

As for your sentence “there is already plenty of genetic variation in virtually every population” … yes… that may be so. But this is NOT the kind of evolution that discussions tend to fixate upon.

There is the famous story of the species of moth with multiple coloration configurations resident in the population (either visibly or as a recessive trait) … and the famous story of the generally light colored population evolving to darker colors during a period of coal-dust pollution … and even evolving back to lighter colors when coal-dust has become effectively controlled.

But the USUAL bones of contention are more about how monkey-like creatures become primates, and aquatic mammals becoming whales.

I think even you will agree that there are no “recessive primate traits” or “recessive whale traits” trapped within the respective predecessor populations… and that without multiple generations of additional mutations … we wouldn’t have primates or whales.


(Benjamin Kirk) #305

As I noted above, many of the major differences appear to be duplications. Do you call those mutations?


(George Brooks) #306

@benkirk,

Maybe I just caught you having a bad day? Generally speaking, I find your views to be quite harmonious with mine… but on some days I can be a little sloppy about how I express myself… and I can understand how that can provoke a reaction for the very precise student of the sciences.

I find the term “trait” sometimes conveys my meaning better than the sometimes useless allele.

We could have dozens of different or new alleles … and still no new traits… But if we have a new physical trait… we are almost CERTAIN that we have a change in alleles.

Oh… thanks for the nudge on the term “primate”. I was thinking about Prosimians… like a Tarsier, and I had never really imagined a Tarsier was considered a “Primate”. But the books say they and all the other prosimians are too.

I learn something every day.

As for your last question: “As I noted above, many of the major differences appear to be duplications. Do you call those mutations?”

If a Chromosome has only one copy of a string of genes… and then a new copy has TWO copies of the very same string - - - that would be a mutation in my book… because the molecule has changed.