The textbook—and misguided—presentation of natural selection

I was reading a nice article by Andrew Shtulman* on the most common misconception people have about natural selection (that it involves not differential reproduction among genetically different individuals but the gradual and simultaneous transformation of all individuals in a population), when I came across his presentation of Darwin’s “variational” theory of natural selection. That’s the first view given in parentheses, and the correct one.

This characterization of evolution via natural selection (it’s not really a definition) involves a three- or four-step logical chain. Here’s the way it’s presented in many classes, and the way I used to present it:

  1. Animals and plants produce many more offspring than can survive, ergo there is tremendous mortality in nature.
  2. Animals and plants differ in their traits.
  3. Bearers of some traits leave more offspring, or survive better, than do bearers of others. (For example, those individual moths who match their backgrounds better are less likely to be eaten by birds than are their more conspicuous relatives.)
  4. Some portion of the differences among individuals in these traits will be passed on to the next generation. That is, some of the variation is heritable (“capable of being inherited”).

If these conditions hold, then the population will undergo gradual genetic change, being enriched in the genetic variants that give their bearers greater reproduction and/or survival (“fitness” is the word we use here). This is a variational view of evolution rather than the incorrect transformational view outlined above.  The chain can also be described as “Excess production of individuals + variation in fitness + some heritability of that fitness = evolution via natural selection.”

I hope you’ve followed me so far. If you’ve taken any evolutionary biology, you’re likely to have heard the chain of logic above. It is exactly the chain outlined by Darwin in On the Origin of Species. Darwin, in fact, said that he finally grasped the importance of natural selection when he read Malthus’s “On Population”, which described the overproduction of offspring. For when Darwin realized that the huge excess of young animals and plants must somehow be culled if populations remained at relatively stable sizes, he saw immediately that the culling would probably be based on the traits that individuals had, and if variation in those traits had at least some genetic basis (remember that Darwin was unclear about how genetics worked), it would, over time, produce a predominance of the variants producing those traits.  Curiously, A. R. Wallace also hit on the idea of natural selection after reading Malthus as well.

But there’s one problem with this: one of the points is not necessary for evolution by natural selection. Can you guess which one?

It’s #1—the very point that brought Darwin and Wallace to the brilliant idea of natural selection.

Why isn’t this necessary? While clearly not all offspring survive in any species—otherwise we’d be up to our collective tuchas in rabbits, beetles, or oak trees—natural selection can still cause evolutionary change in a population that is expanding (or decreasing), and in which all offspring survive. Imagine, for instance, that a lizard makes it to a luxuriant island in the ocean, one loaded with food and without predators. Imagine too that every lizard dies only of old age—after it’s already had its offspring. And further imagine that some lizards are better able to digest the local vegetation, and thus are better nourished and leave more offspring than others. Every offspring survives, but more of the next generation will carry those genetic variants that make them better at digestion. Over time, the population will evolve by natural selection, as the carriers of the “good digestion” genes overtake their dyspeptic confrères.  So we have (variational) evolution by natural selection, but every individual that is born survives to reproductive age. And this will work even if individuals are immortal and never die.

Of course the situation I just described is unsustainable: eventually the population of lizards will get big enough that they’ll be competing for food, and might even kill each other. My point, though, was that natural selection can operate independently of a huge mortality—or any mortality—in a population.

Ergo, we can omit #1 above from the characterization of natural selection. When I realized this, I dropped it from teaching.

In fact, the great evolutionary biologist Ronald Fisher made just this point in his famous book The Genetical Theory of Natural Selection (1930)In chapter 2, he objects to the Malthusian point, saying that it not only ignores differential reproduction in favor of differential survival (my example above), but ignores the fact that organisms often overproduce offspring as the very result of natural selection.  The vast overproduction of offspring in some ocean fish, for example, isn’t just a given: it’s likely resulted from the high mortality experienced by tiny fish, due largely to predation. If that’s the case, you have to produce more offspring just so some will survive.

Here’s the quote from Fisher explaining that. Fisher was famous for his dense and often opaque prose, but maybe you can grasp his point:

“. . . it should be remembered that the production of offspring is only excessive in relation to an imaginary world, and the ‘high geometrical rate of increase’ is only attained by abolishing a real death rate, while retaining a real rate of reproduction. There is something like a relic of creationist philosophy in arguing from the observation, let us say, that a cod spawns a million eggs, that therefore its offspring are subject to Natural Selection; and it has the disadvantage of excluding fecundity [offspring production] from the class of characteristics of which we may attempt to appreciate the aptitude. . . [T]he historical fact that both Darwin and Wallace were lead through reading Malthus’s essay on population to appreciate the efficacy of selection, though extremely instructive as to the philosophy of their age, should no longer constrain us to confuse the consequences of that principle with its foundations.”

Fisher was a very smart man. So, if you teach how natural selection causes evolution, you might want to omit point #1 above—or at least qualify it.


Ronald Fisher (1890-1962)


*Shtulman, A. 2006. Qualitative differences between naïve and scientific theories of evolution. Cognitive Psychology 52:170-194.


  1. Randall Schenck
    Posted July 17, 2016 at 1:36 pm | Permalink

    Thanks to the teacher. So amazing that Darwin and Wallace discovered this so many years ago and yet there are many today…oh well.

    • gravelinspector-Aidan
      Posted July 17, 2016 at 4:48 pm | Permalink

      To quote (I think it was Bohr but I’m not sure, a physicist at least), “progress is made, one funeral at a time.”
      Religion hasn’t had it’s funeral. Yet.

      • Tor
        Posted July 17, 2016 at 5:47 pm | Permalink

        We can only hope and pray….

  2. Raymond Freeman-Lynd
    Posted July 17, 2016 at 1:38 pm | Permalink

    I always present it that this is what Darwin proposed. I then point out that “Nature Red in Tooth and Claw” isn’t really necessary – it’s all about differential reproductive success.

  3. Brad
    Posted July 17, 2016 at 1:48 pm | Permalink

    Although I am not an evolutionary biologist, I want to jump in here and add a “Yes, but…”
    It is easy to think of historical examples of exponential increases (rabbits in Australia, rats or goats in any number of locales, lionfish in the Caribbean,zebra mussels in North American watersheds). The exponential rate of increase is usually rather short before the rate constant decreases or the increase slows and approaches a steady state. This might be due to increased mortality or reduced production of offspring for a number of reasons. Goats, rats or birds might literally destroy the environment that nurtured them. Territorial birds might not be able to hold a territory large enough to provide the resources to feed a clutch of offspring. The first sulfur bacterium to colonise a new sea floor vent could well grow exponentially – until the colony uses all the sulfur in the water, then it is forced into some sort of steady state.
    Exponential increases always end – always. While evolution certainly happens during the exponential phase, I think it is not really the most common scenario. It can certainly favour the genes of the founders, even deleterious genes, and selection does go on.

    As I have said before, thanks for the science posts.

    • Posted July 17, 2016 at 2:29 pm | Permalink

      Actually, one can make a case that selection could be strongest during the exponential phase, which could occur when, say, organisms are invading a novel environment which is benign but to which they’re not adapted (e.g., colonization of an island). It’s of course not the most common situation for any population or species, and in that sense, yes, it’s not”the most common scenario.” But it’s hard to see why selection should be LESS strong during population bursts.

      • Brad
        Posted July 17, 2016 at 6:56 pm | Permalink

        True. And, as you say, the new environment would likely be different from the one the founders are derived from. And you don’t need a big population to get enough variation to have heritable differences:

        In ~30 generations, the offspring of the 5 male and 5 female lizards introduced to an island evolved from insecivores to predominantly herbivorous, with changes in stature, head and jaw structure, behaviour (territorial males to non-territorial), and a gut with cecal valves, a novel feature which improves efficiency of digestion of plant material.

        I’m sure there are other documented examples, the Mediterranean fruitfly invasion in California might be one, or the diversity of flies in Hawaii, although that is more speciation. Still probably overlaps with selection under exponential growth. But the lizards example is well documented, notable, and fast.

  4. Posted July 17, 2016 at 1:52 pm | Permalink

    I prefer the traditional explanation, because it refers to a realistic and sustainable situation. But when I introduce fitness and selection coefficient, I portray a population that is initially of 1000 individuals, of which 200 AA, 500 Aa, 300 aa; in a generation it expands twice to 2000, and the new gene pool is 700 AA, 1000 Aa, 300 aa. Because the carriers of no genotype decrease in absolute numbers, students initially have a difficulty to understand that 2 of the 3 genotypes are being eliminated by natural selection.

    • Posted July 17, 2016 at 2:30 pm | Permalink

      Yes, but my point was that a stationary population is absolutely not required for natural selection to occur, as that syllogism implies.

      • Posted July 17, 2016 at 2:34 pm | Permalink

        I must some day make a collection of the various answers I get when I ask students about the Hardy-Weinberg law. Many of the answers make me pull my hair, and one of the “best” is:

        “The Hardy-Weinberg law says that if mating is random, the number of individuals in the population does not change over time.”

  5. Posted July 17, 2016 at 1:59 pm | Permalink

    I have a sci-fi story about a population of immortal humanoids. They have upregulated heat shock genes and tumor suppressors, their mitochondrial genes are all transferred to the nucleus and are not damaged by reactive oxygen etc. And yes, they have natural selection. Their ruler rapes every female he sees, and because the females have induced ovulation and (of course!) no option of abortion, his progeny greatly exceeds that of other males.

  6. Sastra
    Posted July 17, 2016 at 1:59 pm | Permalink

    This point might be an indirect answer to those who worry unnecessarily over modern medicine’s efficiency. A population in which more offspring survive won’t somehow stop or “regress” evolution.

    • Posted July 17, 2016 at 2:30 pm | Permalink

      However, if this population doesn’t also reduce its birth rate to replacement level, its evolution will stop suddenly when the population exhausts vital resources and brings itself to extinction.

  7. Mark R.
    Posted July 17, 2016 at 2:00 pm | Permalink

    Thanks for this lucid post. Though I must admit I had a hard time following exactly what Fisher wrote. I got the gist of it though because I could follow your reasoning on the population issue. The lizard example was very helpful.

  8. Torbjörn Larsson
    Posted July 17, 2016 at 2:12 pm | Permalink

    Extrapolation to a corner case, since immortal individuals wouldn’t need to reproduce (often). But very illustrative!


    So long ago, and still kicking about today.

    I haz a sad now.

    • Torbjörn Larsson
      Posted July 17, 2016 at 2:14 pm | Permalink

      Ugh, “need”. … which doesn’t mean they wouldn’t display that trait, as a fossil one perhaps.

    • Gregory Kusnick
      Posted July 17, 2016 at 2:30 pm | Permalink

      Immortals might not need to reproduce, but those that do will soon outnumber those that don’t. That’s natural selection.

      • gravelinspector-Aidan
        Posted July 17, 2016 at 4:56 pm | Permalink

        Therefore 100% effective, unavoidable and involuntary sterilisation is needed before the release of $MAGIC_IMMORTALITY_SAUCE$. Particularly if the MAGIC SAUCE is heritable.

    • Posted July 17, 2016 at 2:31 pm | Permalink

      Any immortal individual that had genes for producing offspring would produce natural selection, even if it didn’t “need” to produce offspring. Eventually the population would consist of immortal individuals who reproduced, because there would be no increase in the number of nonreproducing mortal individuals.

  9. amarnath
    Posted July 17, 2016 at 2:12 pm | Permalink

    Thanks, followed by a request to explain JUNK DNA. As a chemist interested in biology, I do not like the word junk. May be dormant or unexpressed parts of DNA. Please…

    • Torbjörn Larsson
      Posted July 17, 2016 at 2:21 pm | Permalink

      Here is a resource from a genome specialist. This is one of his later explanatory posts:

      “About all I had to say, really, was that this is historically inaccurate — “junk DNA” was never dismissed in any major way in the scientific literature. So, the idea that it was is a myth. Does this mean that the concept of non-functional DNA is a myth? Of course not. But let me clarify:

      “Junk DNA myth”, interpretation #1: There is no “junk DNA”, where “junk DNA” is defined as non-functional DNA. That is, there is no non-functional DNA. I do not think this is a myth — lots of non-coding DNA is probably non-functional. However, lots isn’t. It’s not either-or.

      “Junk DNA myth”, interpretation #2: That non-coding DNA was “long dismissed as useless junk but now we’re finding functions”. This is a myth. There was no such period of dismissal. Even if there was, it could only have been between about 1985 and 1995, which is less time than the period since this claim started being made. I have tried to show this by referring directly to the primary literature of the 1970s, 1980s, and 1990s.

      So, to clarify, I do not particularly like the term “junk DNA” because a) it has changed since its original meaning, and b) it clearly is too loaded to be used effectively in objective discourse. I do think there is a large amount of DNA in most animal genomes that does not have any function at the organism level, but I also think some of it has been co-opted for very important roles. The originators of the “selfish DNA” idea thought so too: …”

      “How much is functional? I don’t know, but I can say that since there very beginning — in the first detailed discussion of “junk DNA” ever published — the proposed figure was higher than the current data suggest: …”

      Gregory also describes estimates of functional (in the evolutionary sense) DNA.

    • Posted July 17, 2016 at 2:41 pm | Permalink

      What don’t you like, the word “junk” or the idea of DNA that is junk?

      • Amarnath
        Posted July 17, 2016 at 3:55 pm | Permalink

        In chemistry JUNK is unwanted side reaction.

        • Posted July 17, 2016 at 4:27 pm | Permalink

          Well, we have coding DNA sequences that contains information for the structure of RNA and proteins, regulatory DNA sequences that guide the expression of the coding sequences, replication origin sequences to begin DNA replication, centromere sequences to ensure proper behavior during cell division, and telomere sequences to keep the ends of chromosomes stable. And there is plenty of other DNA for which no function is known, and which does not look like it has a function. E.g. part of it evolves too fast; structures that have a function have some limit on their evolution, because changes in them have to be coordinated with all other structures that interact with them.
          I think “junk DNA” is an appropriate name for these sequences. There are many terms that are differently used in chemistry and biology. E.g. the “antigen-antibody reaction” is not a chemical reaction, and “serum titration” is not chemical titration.

    • jaxkayaker
      Posted July 17, 2016 at 3:53 pm | Permalink

      As with creationists and evolution, and paraphrasing the wrestler The Nature Boy, you may not like it, but you had better learn to love it. There is good evidence that a substantial amount of the human genome is junk, estimated at 90%. Junk DNA is a topic of regular discussion at, written by U Toronto biochemist Larry Moran.

  10. µ
    Posted July 17, 2016 at 2:47 pm | Permalink

    Correct, competition is not a requirement for natural selection to operate.

    This is how I explain this to my students (similar example to JAC’s lizard example, but perhaps easier to understand):
    Suppose you have an environment with unlimited resources (i.e., there can’t be competition between inhabitants because resources are unlimited), and this environment is inhabited by two genotypes of the same species (e.g., two bacterial genotypes living in an unlimited culture broth), one genotype that reproduces fast (every hour), one genotype that reproduces slower (every 2 hours). Both genotypes will increase exponentially in number, but the faster-reproducing genotype will soon outnumber the slower-reproduing genotype. As a result, the faster-reproducing genotype will increase in frequency relative to the slower-reproducing genotype, resulting in change in genotype frequency in this population. This process happens in complete absence of competition (because here the environment offers unlimited resources and individuals do not compete).

    In real life, of course, no environment provides unlimited resources, and therefore natural selection invariably happens under some form of competition.

    But as the above example shows, natural selection can operate in principle in the complete absence of competition, hence competition is not a requirement for natural selection.

  11. rom
    Posted July 17, 2016 at 2:58 pm | Permalink

    There was a TED talk by Susan Blackmore who summarized evolution along these lines.

    For evolution to occur the following three things are required, my paraphrase:

    1) A system that replicates.
    2) There is slight variability in the replication process.
    3) An environment that can selectively eliminate replicates with certain traits.

    She I think reworked this from Dennett and where he got it from I don’t know.

    • Posted July 17, 2016 at 5:15 pm | Permalink

      The one addition we need here is that the traits have to be heritable. Imagine a series of plant clones; they will vary in, say, height due to environmental differences. If taller plants survive better, that will lead to them being more numerous than shorter ones, but nothing will change evolutionarily because all plants are genetically identical.

      • rom
        Posted July 17, 2016 at 8:52 pm | Permalink

        Is that not similar to replicable with variation?

        Here is her version of evolution

        I must admit I like Blackmore

  12. Mark Sturtevant
    Posted July 17, 2016 at 3:13 pm | Permalink

    By Jove! That is right enough! We can strike the high mortality by over-reproduction reference in #1, and if one really wants to hone things to a minimum the survival reference in #3 can also be removed. Its all about differences in reproduction, and it scarcely matters how the matter is decided.

  13. Posted July 17, 2016 at 3:36 pm | Permalink

    “My point, though, was that natural selection can operate independently of a huge mortality—or any mortality—in a population.”

    Which is a good point to bring up when talking to a theistic evolutionist like John Haught. They’re fond of asserting that evolution as it actually occurs is of course the way god would’ve created biodiversity, because it’s the only way. Natch. But if natural selection need not bloody its teeth and claws, then why did god decree that it do so?

    • gravelinspector-Aidan
      Posted July 17, 2016 at 5:03 pm | Permalink

      But if natural selection need not bloody its teeth and claws, then why did god decree that it do so?

      Because if god existed, she’s obviously a sadistic psychopath. Natch!

  14. Jonathan Livengood
    Posted July 17, 2016 at 4:12 pm | Permalink

    Two questions.

    First, do you think it might be worth leaving the high mortality point in as a purely pedagogical device? As you say, both Darwin and Wallace seem to have been helped to see how evolution by natural selection worked in virtue of thinking about overpopulation and mortality. Maybe students today would gain similar insight with such a presentation? After an initial presentation of the four-points, you could follow up by asking students to think about whether #1 is really required and why it might not be. Then they get both the initial insight and a deeper understanding of evolution by natural selection. What do you think?

    Second, a theoretical question. As I understand it, Darwin was explicitly trying to solve the species problem: How do we get new species from a few starts or from maybe only one start? It’s clear to me from your presentation how we get change in an initial population over time without #1. But do we get *speciation*? If all individuals are immortal, will we end up with distinct species after a long run of natural selection or will we end up with something better described in some other way, e.g. a single species with a lot of variation (or a few species corresponding to the number of starts)? I guess I’m just having trouble imagining what the world looks like if all the little gaps between, say humans, chimpanzees, and our most recent common ancestor are filled in by living individuals.

    As an aside: I thought it was funny to see R.A. Fisher described as “the great evolutionary biologist” … not that he wasn’t, but I always think of him as “the great statistician”!

    • gravelinspector-Aidan
      Posted July 17, 2016 at 5:12 pm | Permalink

      As an aside: I thought it was funny to see R.A. Fisher described as “the great evolutionary biologist” … not that he wasn’t, but I always think of him as “the great statistician”!

      Not having formally studied biology since pre-16 exam selection, I’ve never known of him except as a statistician.

    • Pete T
      Posted July 18, 2016 at 3:13 am | Permalink

      If the world we are imagining is filled with immortal beings and has a variety of environments then we would expect large populations of beings well adapted to their particular environments with very small populations of beings with adaptations less well suited descended from those individuals who were slightly better adapted to a new environment than their immediate ancestors. In our world, if somehow every organism survived forever and yet didn’t use up resources, we would expect relatively huge populations of humans and chimpanzees and relatively tiny populations of individuals that represent each generation leading back to our common ancestor. But presumably we would all be struggling to keep our heads above the surface of the sphere of bacteria expanding faster than the speed of light.

      • Jonathan Livengood
        Posted July 18, 2016 at 6:03 pm | Permalink

        Yeah, as you note with the bacteria, the example is … peculiar. I’m still not sure, though, whether having the distribution of beings you describe would count as speciation. But maybe the question is just silly? I guess I was thinking about it like this. I took Darwin to be trying to explain why we have so many species of living beings, where the species are (at least often) obviously different / distinct from one another, and where there are no continuous gradations from one type to the next (today). I was thinking that overpopulation and mortality might do some work in, as it were, *removing the evidence* of our ancestry: removing the in-between beings and thereby exaggerating the differences between the remaining beings.

        • Pete T
          Posted July 19, 2016 at 2:06 am | Permalink

          ‘Species’ is a tricky one and it is a dangerous game to venture an opinion in the front room of the person who literally wrote the textbook on the subject. I think that although there would be fuzzy edges and it would be difficult to define ‘human’ and ‘chimpanzee’ in our imaginary world, it would still be a useful concept and is not that much different to our difficulties in defining the same terms in our real world. As to what we see today as being distinct species only appearing distinct because of the pruning of the extinction of the intermediaries; absolutely.

  15. Posted July 17, 2016 at 4:13 pm | Permalink

    Thank you. I do wish that I were much better educated on these topics and appreciate greatly what you and your knowledgeable readers write about it.

    I find it curious that when some of us talk about overpopulation, we seemingly disregard the great diversity of terrain on the planet that we live on that affects population increase/decrease. Some parts of the planet
    are less amenable to certain life forms and others more so. There hasn’t been (far as I know) nor do I imagine there will be, a consistent rate of overpopulation everywhere on the planet at the same time. Certain parts of the planet are excessively overpopulated. Others (think mountains, canyons, deserts, etc.) cannot be. We haven’t yet gotten desperate enough to build underground cities or cities in the oceans. (Should we count China’s creation of man-made islands in the China Sea, or Singapore’s increasing the dimensions of its’ island,or Bahrain’s palm-tree shaped land extensions, etc?) There are other factors involved in increase or reduction of human populations such as competition with other species, diseases and warfare. Education and religion, also.

    Much as I care about our species at times and what we’ve learned and done (not so much during terrorist attacks and/or idiots firing rifles or assault weapons at people they don’t know), there are times I think that if we go the way of the dinosaurs, it wouldn’t be such a terrible loss. Maybe we would make room for something better to come along.

    • gravelinspector-Aidan
      Posted July 17, 2016 at 5:20 pm | Permalink

      We haven’t yet gotten desperate enough to build underground cities or cities in the oceans.

      It’s very unlikely to come to that. Humankind is already a predominantly urban species, and at urban levels of population density, we’re an extremely long way from running out of space.
      Usable phosphorus, on the other hand, is looming as a mineralogical limitation. (For those not following the issue, all foodstuffs rely on living organisms ; all living organisms use DNA/ RNA as heritable material ; DNA and RNA both require phosphate.
      Mineral phosphate is a finite resource. In terms of biomass, it’s probably going to be the limiting resource.

  16. Posted July 17, 2016 at 4:19 pm | Permalink

    I seem to remember from college one pithy explanation that went:
    Inherited variation+differential survival=>evolution by natural selection
    Like a syllogism!

    • Mark Sturtevant
      Posted July 17, 2016 at 4:48 pm | Permalink

      Similar to one I like (and note reproduction is used instead of survival):
      Evolution by NS is the non-random reproduction of random varieties.

  17. Gregory Kusnick
    Posted July 17, 2016 at 5:30 pm | Permalink

    I thought I remembered this subject coming up before, and here it is, in a comment thread from five years ago.

  18. Marilee Lovit
    Posted July 17, 2016 at 6:18 pm | Permalink

    Great post and comments. Thanks.

  19. Richard C
    Posted July 18, 2016 at 2:38 am | Permalink

    Thanks for that post! I hadn’t thought about how evolution would apply to an immortal population (until natural old age), but that makes perfect sense. It’s about the reproductive success of genes, not simply the life and death of an individual.

  20. Jonathan Wallace
    Posted July 18, 2016 at 2:52 am | Permalink

    Thank you for an interesting post. I guess it is helpful to think of natural selection as operating on differential lifetime reproductive output. Differential mortality may well be (and clearly often is) an important factor in this (you don’t leave any offspring if you get eaten before you mate) but not a necessary one.
    “Survival of the fittest” may be true when the terms have carefully defined meanings in evolutionary biology but is unfortunate in that the every day meaning of the words gives the impression that it is all about mortality and survival.

  21. Dominic
    Posted July 18, 2016 at 3:35 am | Permalink

    Fisher was indeed a smart man. He was also a eugenicist, though of course that does not invalidate his work, it merely places him as a man of his age – so were many others. Thanks for this PCC[E]… always educational!🙂

  22. Gerdien
    Posted July 18, 2016 at 4:12 am | Permalink

    In 1986, the book ‘Natural Selection in the Wild’ by John Endler was published by Princeton UP. Endler gave a succinct and exact description of natural selection, of course without the excess mortality but having the points 2,3,4 above. Endler’s formulation of these points proved exactly parallel to the quantitative genetics description of natural selection.

    The point is that this accurate description of natural selection has been in the literature for ages, and textbook writers are hopeless.

  23. Posted July 18, 2016 at 5:26 am | Permalink

    I would say that point 1 is only misstated, not invalid. Without doubt, exponential reproductive growth is a key factor in the dynamic changes in populations. Point 1 however stresses existence of OVERPOPULATION when it should instead express the influence of COMPETITION. Reproductive success is affected directly by competitive success – the success that individual has in attaining resources that help to increase both survival chances and fitness (in the common meaning of the term). Competitive success then leads to greater “Fitness” in the reproductive sense of the term.
    The mathematics of Evolution are expressed in the models of Evolutionary Game Theory. These models all depend on the existence of COMPETITION.

  24. Posted July 18, 2016 at 7:32 am | Permalink

    Very interesting post. Thanks for this. More brain expansion on a Monday morning (for me).

    This point hits it perfectly: “it … ignores differential reproduction in favor of differential survival”

    And, I think this is the mistake people make when viewing natural selection from the standpoint of the individual body rather than from the gene’s perspective. They are thinking of survival of bodies, not replication of replicators.

  25. Posted July 18, 2016 at 9:10 am | Permalink

    Yes, I agree that #1 is not essential. This is consistent with a number of other considerations:

    * allopatric speciation, whereby new species arise in small sub-populations at extreme ends of the range of the parent species.

    * the “founder effect”, whereby both deleterious genes survive in small populations separated from the parent population.

    * stasis in species over time

    * Prevalence of so-called “missing links” or the “sparsity of the fossil record”.

    I have tried to accept Fisher’s elegant theories, but have failed.

    I just cannot see how an entire species can drift en masse unless its range is so limited relative to body mass and mobility. that gene flow is unrestricted by distance.

    Formerly, I leaned toward the theory of punctuated evolution, but have instead favoured allopatric speciation, as did Gould in his final years. I don’t know where Eldredge stands now, but I fear he may still accept species sorting.

    • Jonathan Wallace
      Posted July 18, 2016 at 11:56 am | Permalink

      It is not at all clear in what sense you consider that the statement “Animals and plants produce many more offspring than can survive, ergo there is tremendous mortality in nature.” not being a logical necessity for natural selection to operate is consistent with all the topics you list.

  26. Posted July 20, 2016 at 2:05 am | Permalink

    While we’re at it I’me not at all happy with point number 2. Point 2 as stated just describes variation. Mere Variation is NOT enough to fully progress evolution by natural selection. Indeed, point 2 reads as though all the potential for further evolution exists in the existing gene pool. Not true. Mutation is an essential “fuel” of variation Mathematically, it allows the exploration of a potential “solution space” in the evolution of a species. The “points of evolution by natural selection are quite simple to state – 1. Competition, 2. Variation, 3. Mutation and 4; Heritability.

  27. Carl Bajema
    Posted September 14, 2016 at 12:12 am | Permalink

    Professor Jerry A. Coyne
    YOUR “The Textbook—and Misguided —Presentation of Natural Selection” on July 17 is a very important problem we educators faee.
    Geoffrey Miller proposed the following solution to help educators and students better understand the difference between NATURAL SELECTION and SEXUAL SELECTION on page 174 in his in his book The MATING MIND (2000).
    Miller proposed that since SURVIVAL is like MANUFACTURING a PRODUCT and COURTSHIP is like MARKETING a PRODUCT that we can help our students better understand the difference between NATURAL SELECTION and SEXUAL SELECTION by thinking about Natural Selection as MANUFACTURING A PRODUCT and Sexual Selection as MARKETING A PRODUCT.

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