Natural Selection


(Paul Lucas) #1

I unfortunately did not get back in time to a discussion with Roger Switele

Roger: “First of all, I understand Darwin to say that Variation plus Natural Selection equals Evolution.
Variation is very different from Natural Selection, because variation is based primarily on genes. Also because Variation is truly random, so that real change can take place. The problem that Darwinism has is that it stops with genes and Variation, neglecting Natural Selection.”

Darwin was very clear that Natural Selection was a 2-step process.

  1. Variation
  2. Selection.

Variation is part of natural selection. There is nothing to select among if there is no variation.
" I think it would be a most extraordinary fact if no variation ever had occurred useful to each beings welfare, in the same way as so many variations have occured useful to man. But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection." [Origin, p 103 6th ed.]

That makes it very clear: variations that are preserved (selected) in the “struggle for life”.

Natural selection does not work under the theory of heredity – blended characteristics – accepted in Darwin’s time. Neo-Darwinism or the Modern Synthesis was the realization that natural selection does work in Mendelian genetics.

But Darwinism does not reject selection. Instead, the allele (form of gene) can persist during selection. Population genetics, which is part of the Modern Synthesis, is natural selection observed in populations and described mathematically. The equations actually describe the effect of natural selection on the frequency of alleles in a population.

Variation is “random” in a very special sense: random with respect to the needs of the individual or the population. Simply put, in a climate growing warmer, just as many deer will be born with longer fur as shorter fur. However, only the shorter furred individuals will do well in the environment.

Roger: “You put the right emphasis on Natural Selection, which determines which alleles will survive and flourish. You just do not separate the two processes which is understandable, because people want to combine them into one. ( Your quote from the Origin goes against Darwin’s use of Malthus to formulate his concept of natural selection, while he used selective breeding for Variation.)”

Darwin combined them into one. Darwin’s use of Malthus comes into play when he said (right before the quote I used above):
"; if there be, owing to the high geometric powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred …"

Malthus noted that population increased geometrically while resources increased arithmetically. Therefore, population would outstrip resources. Notice that Darwin uses Malthus’ concept of geometrical population increase. What Darwin realized was that, since resources did not generally increase in most environments, the population would always be greater than the resources. That is, more individuals than there were resources to sustain. The inevitable result of that situation would be a “severe struggle for life”. This was a metaphorical struggle, not murder. But in this struggle, some variations would be “advantageous” to the individual. Again, Darwin is combining variation, Malthus, and selection.

Darwin did not use selective breeding for variation; he used it for _ natural selection_. The breeder acts as the environment and sets the “struggle for existence”. There are more pigeons born than the environment will support: the breeder will only feed so many. The breeder determines which variations are “advantageous” – how he wants the animal to look or behave. So the breeder decides which variations will be “preserved”.

Darwin does put his discussion of breeding of pigeons in Chapter I – “Variation under Domestication”. But look at the subheadings for the chapter: “Domestic Pigeons, their Differences and Origin—Principles of Selection, anciently followed, their Effects—Methodical and Unconscious SelectionCircumstances favourable to Man’s power of Selectionhttp://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F401&pageseq=1

It’s about selection. It cannot be any clearer. What Darwin (and other breeders) do/did Darwin called “artificial selection”. Because humans artificially set the struggle for existence. Natural selection, on the other hand, was so named because it was the same process happening in nature.


(Peaceful Science) #2

So…this was Darwin’s mechanism for evolution: selection. However,w e now know (since the 1970s) that Darwin’s mechanism is not sufficient. Some would even say it has been falsified as the main mechanism driving evolution.

Evolution, rather, is common descent, and has a wide range of mechanism including natural selection. Neutral drift appears to be quantitatively the most important mechanism.


#3

It’s hard to say what is the ‘main mechanism’ driving evolution. I’d leave that to philosophers to ponder.

There are a number of context-dependent mechanisms at play at various times and it’s hard to untangle or assign the ‘relative’ importance of various interactions. Selection is critical mechanism for many stages. Organisms must be able to function within their environments because as they say, “If your parents didn’t have kids, neither will you”. How all that plays out with the adaptive mechanisms available to organisms can be very complex to dissect. Here’s the thing: ‘natural genetic engineering’ will generate failures as will ‘front-loading’ and ‘morphic resonance’. The products from any of these proposed sources will have to ‘work’ in their environment.


(Larry Bunce) #4

Darwin observed that offspring were not carbon copies of their parents. Even if he didn’t know the exact mechanism that caused this variation, it was obvious that some variants were better able to survive than others. He reasoned that the competitive forces of nature would cause the best-adapted to produce more offspring, so that their traits would become more frequent in the population. He had observed the effects on farm animals and crops of selective breeding by farmers, and reasoned that the selective forces of nature might have that same effect on wild plants and animals.

Darwin used the term “natural selection” in the first edition of On the Origin of Species, but some of his scientist friends pointed out that natural selection implies a natural selector, a non-scientific assumption, so he replaced the term with “survival of the fittest,” a term newly coined by Herbert Spencer, in later editions.

While Darwin did not know the mechanics of heredity, he had observed variation in nature, and came up with an amazingly accurate theory that explained the variety of life we see around us.


(Roger A. Sawtelle) #5

@Paul_Lucas

Thanks for continuing the discussion.

I am on vacation and cannot respond as I would like. Will get back to you soon.

Roger


(Roger A. Sawtelle) #6

[quote=“Paul_Lucas, post:1, topic:5404”]
Variation is “random” in a very special sense: random with respect to the needs of the individual or the population. Simply put, in a climate growing warmer, just as many deer will be born with longer fur as shorter fur. However, only the shorter furred individuals will do well in the environment.
[/quote]

@Paul_Lucas

Natural Selection is not a part of Variation because Variation is random while Natural Selection is determinate.

I so not know why you make the point that Variation is random with respect to the needs of the population. Of course it is. Random is random in this sense and all senses.

But then you go to what is not random in evolution, which means that you are no longer talking about variation which is random, but to natural selection which is not random.

You cite **the example of deer with shorter hair thriving when the climate grows warmer**. While that seems to be true, although things are not as simple as that, an example is not a scientific principle.

The scientific principle taken from what you say, which is basically true, is that Natural Selection and thus evolution is governed by the ecology, the environment defined in the broadest of terms, which determines which alleles thrive and survive and which do not. That is why the dinosaurs dies out when the climate grew cold, and mammals did not a eventually thrived.

@Swamidass wrote: Evolution, rather, is common descent, and has a wide range of mechanism including natural selection. Neutral drift appears to be quantitatively the most important mechanism.

Neutral drift is a mechanism for Variation, not Natural Selection. It is a change of genes over time which is neutral in that it does not basically make the species markedly more or less adapted to the environment. Neutral drift is thus quantitative most important, but not qualitatively most important. Because it is by neutral to Natural Selection, it affirms its importance, rather than minimizes it importance.

@Argon wrote: The products from any of these proposed sources will have to ‘work’ in their environment.

Argon is exactly right, it is the ENVIRONMENT that selects which traits will survive and thrive. This is the point that evolutionary science seems to miss. It is the elephant in the room that no one sees. That you Argon and Paul.

@Larry_Bunce wrote: Darwin used the term “natural selection” in the first edition of On the Origin of Species, but some of his scientist friends pointed out that natural selection implies a natural selector, a non-scientific assumption, so he replaced the term with “survival of the fittest,” a term newly coined by Herbert Spencer, in later editions.

Larry, the scientists friends of Darwin were right, Selection, whether Artificial or Natural, requires a Selector or rational agent. Just changing the term to “survival of the fittest” does not solve the problem. Survival of the Fittest only says that the fittest will survive, which is meaningless. Also Darwin and science did not abandon Natural Selection in favor of Survival of the Fittest, bu8t uses them interchangeably, even though we have rejected the Mathusian population theories they are based on.

Only the concepts of Symbiosis and ecology make sense out of Natural Selection as is demonstrated above.

This is why it is important to differentiate between Variation and Natural Selection, so we can understand how the whole two part process works. Variation “proposes” change or stability. Natural Selection determined if a particular allele will thrive or not by its ability to adapt to its ecological niche.


#7

I’m pretty “middle of the road” or generally aligned with the consensus in evolutionary science. The role of the environment is not missed there.


(George Brooks) #8

@Relates

Why do you keep saying that evolutionary sciences MISS this? I can’t think of anything MORE obvious … and more accepted by Evolutionary scientists.

It is acknowledged EVERY time continental or global ecological systems change.

And during long stretches of time when the ecology DOESNT change, evolution continues as mutations offer refinements of what the environment finds advantageous.


(Roger A. Sawtelle) #9

Then you agree that Natural Selection is determined by the ecology?

P.S. The environment is always changing.


(George Brooks) #10

So the only way I can convince you that I have a balanced view is to state that it is ALL about ecology?

Why don’t you ask: “You agree that Natural Selection is a COMBINATION of ecology and genetics?”


(Roger A. Sawtelle) #11

Because it isn’t. Variation is about genetics. Natural Selection is about ecology. Evolution is a combination of Variation and Natural Selection as Darwin said it was, just not the kind of Natural Selection he postulated.


(George Brooks) #12

@Relates

More quibbling. Why don’t you ask THIS question then - - using your very own words:
“Do you agree that Evolution is a combination of Variation and Ecology?”

I think most all of the BioLogos supporters could get in line to agree with you on this sentence - - using the words you PREFER … if it will get you to stop constantly accusing evolutionary scientists of being imbeciles !!!


(GJDS) #13

Ecology is a relatively new area of scientific research and often, when needed, people may discuss ecology AND biological evolution. As a concept, the area for ecological studies is the entire planetary system, and this would combine the great cycles, such as the carbon cycle, with plant, fungal, animal and any other system such as climate, into a general view of this planet and its life forms.

Because it is a relatively young area, an overall view is extremely difficult to model and discuss with sufficient scientific validity. Most evolutionary discussions deal with microsystems that link a few species with their habitat. I am unaware of any significant insights on major areas of controversy of ToE (e.g. natural selection) that are obtained from such limited ecological studies. I am aware of discussions that purport to show some causal link, but much of this seems to me to be inference at best, and wishful thinking at worst.

In any event, the concept of ecology suggests, at the very least, that we are dealing with a dynamic system that may undergo cyclical changes over geological time scales. This may suggest mainly steady state dynamics, but some may view cycles as quasi-equilibrated, or punctuated equilibrium. In any event, and in all of this, the ability of humans to impact on these cycles is slowly becoming apparent, and would appear to contradict a “law of nature” such as evolutionary natural selection. Evolutionary thinking seems to be stuck with some type of selection to explain the variety observed during such massive cyclical events (although I note the recent suggestions that mutations and neutral shift/drift(?) may be in favour). I find such an outlook inadequate, for the simple reason that we are not in a position to discuss ecological models in great detail.


(George Brooks) #14

Ecology and Evolution - - a partial list of sources …

http://www.sciencedirect.com/science/journal/01695347

Trends in Ecology & Evolution
The Trends Collection includes: Trends in Biochemical Sciences • Biotechnology • Cognitive Sciences • Ecology & Evolution • Genetics • Immunology • Microbiology • Neuroscience • Pharmacological Sciences • Plant Science • Volume 31, Issue 8, Pages 575-656 (August 2016)
IN PUBLICATION FOR 30+ years

UNIVERSITY OF CHICAGO PROGRAM "ECOLOGY AND EVOLUTION"
http://pondside.uchicago.edu/ecol-evol/


Ecology/Evolution Curation Website


In the 124th year of THE AMERICAN NATURALIST (1984)
James H Brown’s article: “ON THE RELATIONSHIP BETWEEN
ABUNDANCE AND DISTRIBUTION OF SPECIES”

FIRST SENTENCE:
“How environment conditions and population processes determine the
abundance and distribution of species is a central problem of ecology and
biogeography.”

UNIVERSITY OF EVANSVILLE


(Roger A. Sawtelle) #15

[quote=“gbrooks9, post:12, topic:5404”]
I think most all of the BioLogos supporters could get in line to agree with you on this sentence - - using the words you PREFER … if it will get you to stop constantly accusing evolutionary scientists of being imbeciles !!!
[/quote]

@gbrooks9

I have never accused evolutionary scientists of being imbeciles, nor do I thi9nk that you and others are stupid because you do not seem to understand what I am saying concerning variation and natural selection.

This issue is not as easy as it appears, which seems to be the reason shy people are quick to take sides between Darwinism and Creationism which are then difficult to discuss rationally. Western dualism indicates that there are only two possible causes, natural or supernatural. There is no place for a third point of view like mine.

Still as Christians and scientists we are compelled to seek the truth and share it with others as difficult and painful as that may be.

@GJDS

I appreciate your point of view. Yes, we need to be careful as to the conclusions we make based on limited knowledge. I think we have enough knowledge to make some basic conclusions, keeping in mind that science must be always open to change.


(Roger A. Sawtelle) #16

@gbrooks9

___The Interaction of Ecology and Evolution _

Ecology and evolution are intimately related because and organism’s ecological situation directs its evolution, and the organism’s response to its ecological situation may be evolutionary_

(from a U. of Evansville course description cited by GB)

This course agrees with what I have been saying, but it takes Natural Selection out of evolution, which is contrary to the understanding of evolution going back to Darwin and continuing to day. It is all part of the question as to what is evolution and how does it work.

It am glad to see change, but as far as I can tell and as BioLogos is concerned there is no consensus on the relationship between Variation and Natural Selection. Of the examples that you produced this last is the only one that seems to me to indicate the kind of effort to integrate ecology and evolution that I have advocated. Thank you, Indiana.

Again I invite others to help me in this effort.


(George Brooks) #17

@Relates

I just can’t believe that any school would teach Evolution and EXCLUDE Natural Selection.

I think you MUST be worrying way too much about specific wording… if you can think there is ANY mainstream program on Evolution WITHOUT Natural Selection.


(Roger A. Sawtelle) #18

@gbrooks9

A) Why are you arguing with your own example?

B) The course defined evolution as common ancestor which is genetic/variation without natural selection.

I am going by what they say, not what I think they should say. I did point out that it was a break with the traditional understanding of evolution. If you have an argument, it is with them and not me.

C) Dr. @Swamidass defines evolution on this web page as common ancestor and I do not see you take issue with this.

E) You keep indicating that you do not agree with my understanding of Natural Selection without giving your point of view. What is it?


(George Brooks) #19

@Relates

You ask me for my definition? I like this one: “When the gene pool of a breeding population changes over time, the net effects of ecological factors, imperfections in the replicating genes, and differential rates of survival and reproduction. The term Evolution applies to changes in a single population, but is especially applicable to two or more populations that become increasingly different from each other, even though they share a common ancestral population.”

But as to your discussion about “Evolution being Common Descent” …

I suspect that if the people at this University knew that there was someone SCOURING THE UNIVERSE looking for the slightest variation in wording that would indicate the proper fixation on ECOLOGY … I don’t think you would have found the wording so devoid of natural selection.

Exhibit Number ONE … a PowerPoint slide … which starts with the very same text you say indicates no interest in Natural Selection … followed by ANOTHER sentence that is ALL ABOUT natural selection - - without using the actual phrase!

As to @Swamidass definition that “Evolution is Common Descent” . . . are you sure that he intended that phrase as the FULL definition? It hardly seems complete in my view. It seems more like a placeholder … since “Common Descent”, while instrumental in the process of Evolution, doesn’t seem to say anything at all that you and I would want it to say:

These 2 words say NOTHING about Ecology … nor do they say anything about Variation … nor anything about Natural Selection.

When we look for an “every man’s definition” of Common Descent, Wikipedia footnotes point us to a useful one:

“In the 1740s, French mathematician Pierre Louis Maupertuis made the first known suggestion in a series of essays that all organisms may have had a common ancestor, and that they had diverged through random variation and natural selection.”

FOOTNOTES:
Crombie, A. C.; Hoskin, Michael (1970). “The Scientific Movement and the Diffusion of Scientific Ideas, 1688–1751”. In Bromley, J. S. The Rise of Great Britain and Russia, 1688–1715/25. The New Cambridge Modern History. 6. London: Cambridge University Press. ISBN 0-521-07524-6. LCCN 57014935. OCLC 7588392, pp. 62–63.

Treasure, Geoffrey (1985). The Making of Modern Europe, 1648-1780. New York: Methuen. ISBN 0-416-72370-5. LCCN 85000255. OCLC 11623262, p. 142.


(Peaceful Science) #20

Well now that I’ve been mentioned 2 times, I’ll weigh in.

This seems like an argument about terminology. An argument about terminology by outsiders to the field. As @gbrooks9 says, scientists do not deny that ecology (environment) determines how natural selection operates. There is no substantive disagreement here. Unfortunately, @relates, there is no substantive contribution you are making (sorry). This appears to be an argument about how to explain evolution, and nothing more.

Clarifying my prior comments, I’ve said that the only consistent definition of evolution in history is “common descent.” That is the high level theory. The low level mechanisms are constantly being revised. But revisions here have no bearing on “common descent,” which has a mountain of evidence supporting it. This, also, is where all the theological controversy is. I see little (no?) value in arguing about mechanisms.

This article by YEC Todd Wodds is helpful:

This can be seen in history also. Darwin only partially triumphed in his lifetime. He convinced most scientists that common ancestry was true, but the majority of his friends and colleagues remained skeptical of natural selection. In other words, the evidence Darwin presented to argue for the high level model of common ancestry convinced most readers of Origin, but they generally disagreed about his low level theory of how new species originate. In this way, I find it unfortunate that some creationists today doggedly attack the neodarwinian synthesis, a particular low level theory to explain the origin of species, as if the acceptance of the high level model of common ancestry depended on it. I assure you that the evidence of common ancestry does not depend on any particular low level theory of the mechanism of evolution. The history of science between 1859 and the 1930s bears this out: Nearly everyone accepted evolution, but few agreed on how it happened. Even if the neodarwinian synthesis could be discredited (and that’s a big if), acceptance of common ancestry would be unscathed.

http://toddcwood.blogspot.com/2009/10/nature-of-explanation.html

The mechanisms of evolution are constantly being revised. But evolution, defined as “common descent,” has greater than 99% agreement among biologists over the last 150 years. This, once again, makes the terminology debate among outsiders to the field almost entirely irrelevant.

@relates you have a point on substance, but the argument about vocabulary is superfluous, especially because there are hosts of mechanisms that are important too (beyond ecology) that you do not mention either. All of that is part of the “modern evolutionary synthesis.” That is the best term to use right now.