…and this is a 
What? Only 50 myths?
Category: Creationism
Posted on: August 21, 2006 8:46 AM, by PZ Myers
Over at the Raving Atheist's forum, contributors have compiled a list of 50 evolution myths. It's actually at 51 right now—I could have told them there are a lot more than 50—but it's entertaining. Now they just have to get cracking on 51 rebuttals to the myths. A lot of them are in the Index to Creationist Claims already.
1) Evolution gives you what you need
2) We popped out of monkeys one day
3) The theory of evolution is tied to the big bang theory
4) The theory of evolution says random chemicals mysteriously made the first cell
5) Darwin took back his theory of evolution on his death bed (that's an urban myth created by Christians)
6) They eye accidentally formed itself somehow.
7.) That things evolve 'magically' without selection involved. It's just some slow process...At least this is what I believed as a kid!8.) That evolution equals eugenics.
9.) That it has a GOAL.
10.) That it can happen to anything, even watches and pottery.
11.) That it's a scientific conspiracy theory we believe in to battle Christianity.
12.) That evolution equals atheism.
13.) That there is an actual difference between micro and macro-evolution
14.) That it is a 'Random' process.
15.) That there are no transition fossils
16.) That humans evolved from the Apes that are around today.
17.) The second law of thermodynamics makes evolution impossible.
18) If evolution is true, how come there are still monkeys?
19) Evolution requires faith.
20) Survival of the fittest means organisms should go kill off weaker members of its species to make survival easier for the stronger members.
21) Physical changes that occur during the lifetime of an organism will be passed on the offspring.
22) Survival of the fittest is circular logic.
23) Only the fittest survive. (In actuality, if an organism can barely get by then it classified into the "fit" category).
24) Kent Hovind is an expert in the fields of evolution, biology, and other sciences.
25) Organisms evolve/mutate during their lifetime if a new selection pressure exerts itself.
26) Evolution caused slavery.
27) Many scientists are now casting doubt on Darwin's theory.
28) Charles Darwin is Satan.
29) Evolution can't exist because of irreducible complexity.
30) Evolution is JUST a theory.
31) God made evolution so he could trick as many scientists as he could into believing it, instead of him, just so he could light them on fire for all eternity. But he still loves them.
32) Man and dinosaurs existed at the same time. T-Rex used to be a vegetarian
33) 'Darwinists' claim that any criticism of the theory of evolution is unscientific
34) Evolution is effectively refuted by 'the Cambrian Explosion'
35) Scientists "believe" in evolution.
36) There is great strife in the scientific community over evolution.
37) Kent Hovind is a brilliant man!
38) Evolution can't explain love.
39) If evolution is true, why are there homosexuals?
40) There are no transitional forms: One species gives birth to another! Through magic!
41) If you believe in evolution, then that means you think it's okay to kill, rape, and steal
42) Evolution is not testable or empirical, therefore it is not science.
43) No Darwin, then no Hitler
44) The perfect match between bees and flowers must be a designer because it can't be evolution.Evolution has to do with survival from predators, not how well you can carry pollen.
45) Mutations are never beneficial
46) There is limits to biological change: new kinds never arise
47) Vertebrate embryos never resemble each other
48) Evolution must be wrong because gravity pulls things down right, but that clearly doesn't happen because birds can stay up in the air.
49) Oh you evolutionists make me laugh, it was God who created the world. It says so in the bible and the bible says its true, so IT IS TRUE!!!
50) Evolution was responsible for the Columbine high school shooting
51. Evolution can never be proven because we didn't see it occur.
By the way, #13 is not a myth. There is a recognized difference between micro- and macro-evolution. The myth creationists use is that macroevolutionary events are somehow less well supported than microevolution—they're wrong.
Comments
Seems to me that #30 is no myth either. Evolution _is_ just a theory, in the same way that Newton's ideas about gravity and Einstein's thoughts on relativity are just theories.
Posted by: flack | August 21, 2006 9:15 AM
I agree. Macroevolution and microevolution are decoupled in many ways so #13 is actually not a myth.PZ says,
I've posted a little note about this at Macroevolution.
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Posted by: Larry Moran | August 21, 2006 9:19 AM
The myth creationists use is that macroevolutionary events are somehow less well supported than microevolution.
I do not understand why creationists do not recognize marcoevolution happened, yet they accept macroevolution. This tells me that they accept some part of evolution as fact.
Posted by: Corey Schlueter | August 21, 2006 9:19 AM
Whoops, that should be "yet they accept microevolution" (not marcoevolution).
Posted by: Corey Schlueter | August 21, 2006 9:22 AM
This one is also misleading. Much of evolution is effectively "random" for many meanings of the word "random." What the author probably meant to say was that natural selection isn't "random" but even that requires qualifications.For those who are interested in more information, I've put up a little essay on the topic at Evolution by Accident.
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Posted by: Larry Moran | August 21, 2006 9:25 AM
Micro and Macro can be seen as the same, or sharply different. It matters mostly on how one defines the two. I personally separate the two based on how I desire to define them, but in reality, no one has set up universally accepted definitions of these two concepts which do not allow for grey areas. This allows people, if they so choose, to view the two simply as different poles on a sliding scale from minor variations in size, shape, color, physiology...to speciation...and finally novel trait development that are used by people in an arbitrary manner to separate groups (For example, as reptiles from mammals).
Posted by: Lago | August 21, 2006 9:51 AM
"Organisms evolve" is a myth, all by itself, and a persistent one. You don't need to mention the rest of (25). Evolution is not about individuals.
Posted by: TomS | August 21, 2006 10:21 AM
"Much of evolution is effectively 'random' for many meanings of the word 'random.'"
I'm not a scientist, so I could have this all wrong. But I struggle with the notion of randomness in this context. The mutations that occur within a species over generations have no regard for selection pressures -- they would occur with or without them. I think this is what folks are thinking of when they describe the mutations as random. But random doesn't really nail it for me as a descriptor. It implies haphazard and inconsistent. To me, these mutations look more like relentless and consistent attempts at diversification.
Posted by: flack | August 21, 2006 11:01 AM
flack- mutations aren't "attempts" at anything, they're mistakes in DNA replication or imperfect repairs of DNA damage. In other words, sh*t happens.
Also, as you'll find out if you read Larry's essay (as I highly recommend you do), he is also speaking of the importance in evolution of genetic drift- a prototypical random process if ever there was one.
Posted by: Steve LaBonne | August 21, 2006 11:14 AM
PZ, could you explain what this difference is?
The prefixes micro- and macro- imply a dichotomy of scale with no continuity between the two. Yet, it seems that most evolutionary biologists would agree that changes in gene frequencies in populations lead to speciation. Where does one draw the line? When two populations are sufficiently distinct to be called two species? When species have accumulated 1 million years worth of genetic differences? 10 million? Or at the other end - one generation's change is micro- while two generations is macro-?
Posted by: cserpent | August 21, 2006 11:18 AM
definitions of 'microevolution' and 'macroevolution', as I understand them :
microevolution any evolution that a creacionist can not deny without perceiving himself foolishness of such denial
macroevolution any evolution that a creacionist can deny without perceiving himself foolishness of such denial OR any evolution of homo genus.
If there is something I got wrong, feel free to correct me here :-)
Posted by: T_U_T | August 21, 2006 11:22 AM
Wow, PZ. Thanks for the recognition. Keep checking back, I'm sure we will have more fun with that thread. With all the talk of macro vs micro, let me ask you this: Mayr's definition of macroevolution is "evolution above the species-level." Is there a technical difference between macroevolution and speciation?
Posted by: Tenspace | August 21, 2006 11:33 AM
It looks like an excellent essay, very accessible to a curious non-scientist like myself. I'm going to have to go back for a more thorough read.
This caught my eye:
"We all know what we mean when we talk about chance events or accidents. We mean that such events are not predictable by any means at our disposal."
So here's where I get hung up: we know that these mutations occur, and have done so for a very long time. Sh*t happens, as you say, and that same kind of sh*t has been happening since the begining of life on this planet (yes?). So that part of the whole system of evolution -- the so-called random mutations that feed the Random Genetic Drift Larry describes in his essay -- that doesn't seem very random at all to me. If it happened only occasionally, sometimes, sometimes not, in this species but not that one, then it would look random to me. But instead it happens consistently, across all species all over the planet (I think -- is that true?) So rather than being a "chance event" that is "not predictable by any means at our disposal" as Larry defines it, it seems to me that this process of diversification through genetic mutation is entirely predictable. It happens all the time and will continue to do so. The particular results of the process -- what the specific mutations will be and which ones will turn out to be advantageous -- may not be predictable, but as a whole, this process looks anything but random.
Posted by: flack | August 21, 2006 11:45 AM
Thank you, PZ. Well done!
Posted by: Philboid Studge | August 21, 2006 11:47 AM
Imagine a primitive hominid population that spits into two distinct populations. One leads eventually to Australopithecus robustus and the other leads eventually to Homo sapiens.cserpent asks,
Explain, using microevolutionary concepts only, how this split occurred and why A. robustus is extinct while H. sapiens survived.
Nobody denies that microevolution is part of macroevolutionary explanations--we just point out that they aren't sufficient to explain the sorts of things that macroevolutionary biologists want to explain.
You illustrate one of the problems with the sufficiency of microevolution argument. Your question focuses on the generation-by-generation changes in a lineage but ignores the important problems of explaining cladogenesis and extinction. It's like not seeing the forest for the trees. You have to explain the pattern and not just the individual lines.
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Posted by: Larry Moran | August 21, 2006 12:09 PM
"evolution by accident" is an accurate description of how evolution occurs. - from Moran's essay.
So, by analogy: is all the attention and analysis lavished on the stock markets justifiably motivated by only the stochastic processes which generate the great majority of each stock's price (value) fluctuations?
Posted by: thwaite | August 21, 2006 12:09 PM
PZ,
If possible, please do a full post on the difference between micro and macro evolution. I'm no biologist, but it seems to me that there is no difference: "changes in gene frequency" in a population are all "micro" changes, that may or may not be expressed on a "macro" scale. Isn't it simply a matter of degree rather than difference of "kind?"
Posted by: dogscratcher | August 21, 2006 12:15 PM
Could you explain first, which concepts are microevolutionary only, and which ones are distinctly macroevolutionary ?
Posted by: T_U_T | August 21, 2006 12:20 PM
If possible, please do a full post on the difference between micro and macro evolution.
As a person with no biology credentials, my understanding is that the microevolution/macroevolution distinction is totally bogus, no?
Posted by: George Cauldron![[TypeKey Profile Page]](http://scienceblogs.com/pharyngula/nav-commenters.gif)
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August 21, 2006 12:21 PM
flack says,
If you don't like the word "random" then feel free to substitute any other word that conveys the essential meaning. I've decided to use "accident," as in "evolution by accident," precisely because I want to avoid semanitc quibbles about the exact meanings of "random" and "chance."
The point is that there's a lot more chance and accident in evolution than most people admit. When you say that evolution isn't random you are denying an essential, and well-documented, element of evolution at many levels.
This is where Richard Dawkins should jump in--I know he's reading this ....
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Posted by: Larry Moran | August 21, 2006 12:24 PM
"Mayr's definition of macroevolution is "evolution above the species-level."
Tenspace: Go into a roomful of systematists, ask what constitutes the species level, and then stand back with a body shield and a Taser for if the melee gets too close. I spend almost three lectures in my evolution class on species concepts, and I barely touch on the basics. A "species" is just a construct that people use to define a particular group of organisms. They can be based on relationships, characteristics, biochemistry, all kinds of things. One of the limitations of Mayr is that he's an ornithologist, and used to creatures that tend to keep themselves separate, and tends to fixate on them. Try using his definition of species on grasses. Or bacteria. Even among people who define species in the same way, there's always argument on how to divide genera and species, and when to collapse and when to split, and where this weirdo variant fits in, and so on. A species is not a magical entity with a wall around it (although most Creationists seem to think that it is). That definition of macroevolution is absurd, because there's no way to define the "species level" in the first place. That's basically my beef against the distinction between micro and macro in the first place - everyone would draw the line in a different spot.
Posted by: Carlie | August 21, 2006 12:46 PM
flack, what I think you're not getting is that mutation rates are typically VERY small. We may, for all we know, be looking in many organisms at the minimum attainable rate of errors- there has undoubtedly been pretty intense selection in that direction, as the elaboration of DNA repair systems will attest. In that view genetic change of populations over time is simply an inevitable, biologically "unintended" (so to speak) consequence of the laws of chemistry and physics, so your "predictability" really is an empty concept. The alternative is the various group-selectionist arguments for "evolution of evolvability", which seem dodgy to me though they certainly have been defended by people far smarter than I am.
Posted by: Steve LaBonne | August 21, 2006 12:51 PM
I always assumed the micro vs macro false dichotomy is one springing from the the myth that something must be observed to be factual.
For example, creationists can sometimes find it difficult to deny the evolution of bacterial resistance, and so the invention of microevolution helps them over that particular hurdle.
Posted by: Blader | August 21, 2006 12:53 PM
I can't believe they forgot PYGMIES AND DWARVES!
Posted by: Gregory | August 21, 2006 1:00 PM
Larry - thanks for responding. And please don't mistake my curiosity for argumentativeness. If I'm quibbling it's only an attempt to fill in gaps in my own non-expert understanding.
I suppose you're right that it really comes down to a semantic issue of what we mean by random. If we look at the level of individual genetic mutations, then yes, random, accidental, chance, these seem appropriate.
But to look at the process as a whole, where we see all these species cranking out a steady flow of mutations, generation after generation, it starts to look less random and more like some kind of evolutionary constant. At that level, certainly there is an element of chance in play, but "random" falls short of describing the bigger picture. Sure there is a factor of randomness, even a very important factor as you write in your essay. But does that then mean that the whole process of evolution should be considered random?
Posted by: flack | August 21, 2006 1:07 PM
Again, flack, nothing is being "cranked out"; mutations are simply unavoidable (and to all intents and purposes random) noise in the transmission of genetic information. It's not physically possible for organisms to stop "cranking out" mutations.
Posted by: Steve LaBonne | August 21, 2006 1:16 PM
Gregory--
Sorry to nitpick, but it's "PYGMIES + DWARVES!"
Posted by: JakeB | August 21, 2006 1:18 PM
Well, the concept 'random' is a pretty tricky one - and your confusion seems to be less about the biological specifics than randomness in general, so I'll take a shot at an explaination.
The answer to the question 'is X random?' depends entirely on scale. (Almost) all random phenomena behave at least quasi-deterministically if you look at a large enough population.
Take, for example, a rigid container full of gas, with a moveable piston in one end.
Such a container contains (no pun intended) something to the order of 10^23 molecules, if the pressure in the container is in the same region as the atmospheric pressure. We cannot - literally cannot, as in 'can be shown to be impossible even in principle' provide a deterministic description of the motion of a single molecule around the box. This motion is random in all reasonable interpretation of the word.
This does not prevent us, however, from predicting which way the movable piston will go if the pressure inside the container is different from the pressure on the outside. This motion is not random in any reasonable sense of the term.
So, is the motion of the gas random? Well, if you look at the molecular level, it is random. If you look at the macroscopic level, however, it is most definitely deterministic.
The same kind of reasoning can be applied to the example of mutation.
On the atomic level, mutation is indeed random. Taking any given piece of the reproduction process, it will be impossible to say whether or not it will contain an error or fail to rectify a previously introduced error.
(Sure, for every known species there is a non-zero chance of a mutation in any cell during any given division, but that does not, in any reasonable sense of the term, make the process non-random.)
But on the species level, we can say conclusively that mutations will occur. We can even come up with some ballpark figures for the frequency of such mutations. But this is simply an issue of dealing with sufficiently large numbers.
There are 6.5*10^9 humans on this planet. There are manyfold more humans that have died already (probably by a couple of orders of magnitude, depending on your preferred definition of 'human').
If you take 6.5*10^9 random events, you get something that's at least quasi-deterministic most of the time, just as you get something deterministic from taking 10^23 random molecular motions in a container.
OK, there's quite some way from 6.5*10^9 to 10^23. But consider that each human has a number of bacteria in his gut that's about comparable to the total number of humans in the world - and that these critters duplicate and die and duplicate every day, and you get a truely staggering number of birth events over the lifetime of a human.
Easily above the 10^23 random motions it took to make a non-random, macroscale motion in the gas container.
So, is mutation random? When talkning about a single individual, it most certainly is. When talking about an entire population, over an evolutionary timeline, it is more like quasi-random.
Of course, selection pressures often behave as chaotic systems, but that's a whole 'nother kettle of fish, and this post is too long already.
- JS
Posted by: JS | August 21, 2006 1:30 PM
Carlie said:
"That definition of macroevolution is absurd, because there's no way to define the "species level" in the first place. That's basically my beef against the distinction between micro and macro in the first place - everyone would draw the line in a different spot."
Yes, my point exactly. As I do use the terms as seperate myself, I do so for my own arbitrary reasons that are far from universal.
I choose to draw the line based on what most creationists would view as "Kind-to-Kind". When I debate a creationist, it is always best to find where they define the "kind" line, and then debate them at this point as to not waste time.
I find most creationists are rather simple-minded (surprised?) and "Kind" is usually defined as, Cat, dog, horse, as well as Mammal, reptile, bird ect...
This means "Macro" is what ever separates these groups, as oppossed to "Micro" which is whatever is within these groups...
Posted by: Lago | August 21, 2006 1:35 PM
By the way, just for old times' sake, I'll opine that Larry and Dawkins don't fundamentally disagree but are simply talking at cross purposes by way of their different rhetorical emphases. Dawkins does not deny the random element in evolution; if he did he'd have, for example, to reject the use of molecular clocks. Larry obviously does not deny that populations become better adapted to their environment via selection. Dawkins, understandably in his books addressed to non-scientists, feels the need to (over)emphasize the perfection of adaptation to counter creationist propaganda which aims to deny the existence of any non-random element in evolution, thereby rendering the appearance of design inexplicable execept by invoking Big Daddy in the sky. Larry, equally understandably (and especially because his professional focus is molecular evolution, where drift is highly visible), wants to promote scientific accuracy by countering the mistaken impression that Dawkins's readers may well receive that there is no significant non-random component in evolution (beyond the occurrence of mutations). I can see where both are coming from, and the "war" seems a bit overblown to me.
Posted by: Steve LaBonne | August 21, 2006 1:35 PM
That should be "no significant random component", not "non-random". Sorry.
Posted by: Steve LaBonne | August 21, 2006 1:38 PM
Larry Moran wrote:
This defines macroevolution as description of patterns and microevolution as mechanistic explanation. In that case, I would say the distinction isn't particularly important. That is, macroevolutionary explanations aren't really explanations so much as descriptions.
Microevolutionary explanations (mutation, natural selection, sexual selection, genetic drift) seem to work pretty well as mechanisms explaining population-level changes that, in allopatry and over long timespans lead to cladogenesis. I don't think that other explanations are necessary.
I suppose one could argue that allopatry and long time spans add a context lacking from those explanations. In that case I would say that microevolution so defined is incomplete and that macroevolution completes that definition, rendering both terms unnecessary and easily handled by just one - evolution. (Before someone chimes in about sympatric speciation: yeah I know it requires different explanations from allopatric speciation but I don't think it has any relevance to the macro-/micro- question.)
Also, a pet peeve - extinction is not evolution nor even a part of it. It is a separate phenomenon.
Posted by: cserpent | August 21, 2006 1:42 PM
Thanks Steve, I think you've stated very well the minor 'balance of forces' differences between adaptationists and randomists (not a word - until now).
Is evolution adaptive or accidental? The answer is: "yes".
Posted by: thwaite | August 21, 2006 2:12 PM
Lets put it this way, Flack.. Statistical predictability isn't the same as "actual" predictability. While its unlikely, its not impossible, for the single member of a species to suffer "no" noticable mutations in some arbitrary period of time. Its also possible, even without some external condition causing it, for a member of a species to have double the normal mutations. On average we can say that X number happen, sans external forces like radiation, in a Y period of time. The individual events are not predictable, even if, like a coin toss, the average, over time, is X at Y rate. This is why its a semantic issue. It "is" random, but it is also, to some extent, "predictable", just not in any sense that makes one bit of difference to the guy trying to guess when, how or what the mutation is likely to be.
Of course, some regions of DNA are more susceptible to others, to you can bet on which one "might" change, for much the same reason that someone was able to build a device to predict Roulette. If the odds of certain results can be skewed, but you know enough about the physics, you can predict which segment of three slots the ball will land in. With DNA, if you know which regions are prone to mutation, you can guess which "region" might show a change. You could also be dead wrong, just as the Roulette predictor failed because it couldn't account for the ball hitting one of the raised diamonds on the outer edge, if the ball hit it.
There are serious problems trying to use "random" *or* "predictable" when talking about mutation. The meaning of them is entirely contextual, dependent on what scale or time frame you refer to and have vastly different meanings, depending one what scale and time frame you are referencing. But in no case does the former mean, "100% impossible to predict", or in the later case, "100% certain." It would be like me predicting not just how many cars will pass by my house today (and not being allowed to cheat by predicting them individually), but the precise color each of them will be and what order they arrive. Knowing what cars my neighbors drive and their work schedules would only net me "maybe" 70%, but only because I knew what "usually" passed by my house. If I was living next to a freeway, that would get a whole heck of a lot less certain. lol
Posted by: Kagehi | August 21, 2006 2:31 PM
Thanks JS -- your molecules/piston metaphor seems very apt. Looked at from a planetary scale, the whole process tends to appear more deterministic. Zoom in to the level of individual organisms, or molecules, and the randomness is more apparent.
Steve -- Evolution of evolvability, huh? I'm going to have to ponder that one for a while. The notion of a "minimum attainable rate of errors" is fascinating though. It conjures up an image of two competing forces at work: on one hand, the greater the diversity of mutations a species produces, the better the odds that one of those mutations will prove advantageous. On the other hand, too high a rate of mutation could be a problem for the species' survival. I guess it's not surprizing to hear that the equilibrium lies somewhere near the "minimum attainable rate of errors".
Anyway, my grasp of all this is pretty basic, and probably a little exasperating to the specialists in the house. Thanks for some enlightening Monday conversation.
Posted by: flack | August 21, 2006 2:43 PM
I would have to take cserpent's side on this one - although I would stress that there are respectable opinions on both sides of this genuine debate in evolutionary biology. In fact, the most recent issue of Science that crossed my desk (which I have regrettably not had time to read) had a comment on this topic by Jerry Coyne in the form of a reply to Davidson and Erwin, Science 311, 796 (2006). Davidson and Erwin took a position more similar to Larry Moran's.
The big question to me is whether something fundamentally different has to change to generate a "macroevolutionary" change. The big point is that I think it is perfectly respectable to take either opinion at this point in time.
I think this is a bit unfair - you have to admit that the question is moving toward the Hovindesque "if you can't explain the whole universe using your hypothesis it must be wrong!" We may never be able to explain all of the details of A. robustus extinction and H. sapiens survival. But it may be possible to establish some pathways of that type. I'm not sure how many examples we would have to find to push the notion that microevolution can explain macroevolution into the "most plausible hypothesis" category.
My favorite example of a charater that would appear "macroevolutionary" in nature that potentially could be explained through microevolutionary concepts is oviparity/viviparity. Many squamates lay eggs that are about halfway through development - earlier laying reinforces oviparity, longer retention leads to viviparity. It is not unreasonable to expect the period of egg retention in the female to be heritable, and mutations would be expected to alter it. On the extreme, failure to develop a shell coupled with transport of gasses and nutrients across the chorioallantoic membrane would yield a placenta.
Within the squamates, all modes of reproduction are evident, as are many intermediates. So something that would seem highly discontinuous in mammals (ovoviviparity with a yolky placenta in marsupials vs a complex placenta in eutherians) can be seen as continuous in another group of organisms.
I hope Larry doesn't take umbrage at the statement about his question - I think this debate is interesting and about a much more "real" issue than anything out of the creationist/ID camp. Some of it is philosophical - for example, would a change in ASPM that leads to a large brain size increase be within the realm of microevolution? What about a regulatory gene like teosinte branched in maize? I would say that they are, but I suppose there are ways in which they could be conceptually separated from standard microevolution. It is too bad that folks like PZ and others have to fight the good fight against the creationist/ID folk - talking about the genuinely open aspects of evolutionary theory would be more fun.
Posted by: Edward Braun | August 21, 2006 3:28 PM
Steve LaBonne says,
I agree. I don't understand why some evolutionists make such a big deal about evolution being non-random when it's clearly untrue. Perhaps it's because these same evolutionists want you to think that organisms look "designed" instead of a mixture of sloppiness, maladaptiveness, Rube Goldberg construction, accident, and "design."
By harping on the (false) fact that organisms are designed they play right into the hands of the Intelligent Design Creationists. We need more emphasis on the fact that much of evolution doesn't look designed at all.
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Posted by: Larry Moran | August 21, 2006 3:28 PM
flack asks,
No, not all of evolution is accidental or random. Natural selection is a non-random process although it's effect is often exaggerated. How many people know that there's an important stochastic component to natural selection? Most beneficial alleles are lost before they ever become fixed in the populations.
The other point about natural selection that's often ignored is how the direction is determined not only by the accidental fixation of certain alleles but also by whether the mutations ever arose in the first place. This is why modern mutationism is much more important than most people realize.
Here's one of my favorite quotes from Doulgas Futuyma,
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Posted by: Larry Moran | August 21, 2006 3:38 PM
Posted by: Steve LaBonne | August 21, 2006 3:45 PM
Edward Braun wrote,
I think you missed the point. In order to explain the formation of new populations and the death of old ones you have to go beyond population genetics. You need to look at various mechanisms of speciation and extinction and you need to consider the environment and what was going on when the event occurred. It's not something that you can just casually dismiss as "microevolution."
That's what people need to understand about macroevolution. It's the field of study that deals with common descent and the unique history of life. You can pick out any known trait and say that a mutation occurred and the allele became fixed in population X. But that's not sufficient for macroevolutionary biologists. They also want to know why that mutation occurred and not some other. They want to know why it became fixed when it did and not five million years earlier. They want to know why that particular species was affected and not others. None of these questions can be answered by appealing only to population genetics.
There are dozens of interesting questions that have been used to illustrate the importance of macroevolutionary biology. One of my favorites is why there were no large placental mammals in Australia. Do you think this question can be answered by population geneticists? How about a population genetics explanation of mass extinctions or the origin of mitochondria? Is that possible?
Of course it's not. Your explanations will involve microevolution at some point - how could they not? - but it won't be sufficient. You'll also have to mention plate tectonics, asteroid impacts, and endosymbiosis, no?
And we haven't even begun to talk about species sorting ... :-)
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Posted by: Larry Moran | August 21, 2006 4:09 PM
The use of the word decoupled here puzzles me.
If microevolutionary explanations (NS, SS, GD) are part of macroevolutionary explanations, how are the two decoupled? If they aren't, then what is a macroevolutionary explanation and what does it explain?
I don't disagree that to explain the grand diversity of life, one has to invoke the enormity of geological time and geological events on vast scales, including catastrophic ones. But evolution occurs by little steps. Those steps may be really fast or very slow depending upon mutation rates, generation times, population sizes, and selective regimes, and there are occassional, but very rare, big jumps (whole genome duplication anyone?), but even whole genome duplication is just one big mutation that is immediately subject to selection and drift - the realm of microevolution. The prefixes macro- and micro- are unnecessary. It is all one process of changes in the heritable characteristics within and among populations of living things across generations leading to a branching pattern of ancestor-descendant relationships. One word, evolution, encompasses those changes, from the simple generation to generation shift in gene frequencies to the substantial mega-generational differences between phyla. I don't think one can separate the large timescale patterns from the small timescale processes. Where do you draw the line?
Posted by: cserpent | August 21, 2006 6:34 PM
I'm not sure what you were asking here. The Australopithecus-Homo split may be explained by standard evolutionary mechanisms (NS, SS, GD) and allopatry or one of the sympatric speciation hypotheses if it occured in sympatry. Because the most recent A.r. fossil predates the earliest H.s. fossil by over 1 million years, the survival of H.s. is an entirely separate phenomenon from the extinction of A.r.. They require two separate explanations.
But how about a much more dramatic example, such as the diapsid-synapsid split and subsequent radiations? The fossil record provided a beautiful series of transitional forms for the evolution of synapsids from a common ancestor shared with diapsids and similar transitional forms for modern diapsids. Which part is macroevolution - the earliest detectable split between the clades or every branch point along the way in each clade? All of the above? Or would you argue that the diapsid synapsid differences don't represent macroevolutionary differences? That would be a hard argument to make while simultaneously claiming that the Australopithecus-Homo split represented macroevolution. This why I see the macro-/micro- dichotomy as a false one. It is simply evolution.
Posted by: cserpent | August 21, 2006 6:35 PM
I think Mr. Ham has confused genetics with genesis. Afterall, it's only off by a few letters -- not much of a mutation.
Posted by: Rhampton | August 21, 2006 8:11 PM
cserpent says,
Microevolution is evolution within a population (i.e., change in the frequency of alleles). In order to explain cladogenesis you need to add something else to describe how the two nascent populations became physically separated and how they became genetically isolated.
Did the extinction of one species have anything to do with the survival of the other? If so, that would be one example of a higher level phenomenon that can't be explained by the changes of allele frequency within a population. Even if the extinction and survival were completely independent, the extinction of one hominid lineage is an interesting historical event that calls out for an explanation. That explanation isn't likely to be completely covered by standard microevolution theory alone.
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Posted by: Larry Moran | August 21, 2006 9:33 PM
Steve LaBonne says,
It's clear that something needs to be done. All you have to do is look at the comments posted above to see the extent of the misinformation that's been spread by Dawkins and his fellow ultra-Darwinians.
In my opinion, the best way to counter the extreme one-sideness of their books and articles is to present a strong case for the other point of view. That may require a few extreme statements in order to get everyone's attention. I realize that for people like you that's not necessary.
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Posted by: Larry Moran | August 21, 2006 9:40 PM
cserpent says,
It's the standard terminology. Don't try to parse it any more than you have to. It simply means that microevolution is not sufficient to explain all macroevolutionary phenomena.
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Posted by: Larry Moran | August 21, 2006 9:44 PM
"Microevolution is evolution within a population (i.e., change in the frequency of alleles). In order to explain cladogenesis you need to add something else to describe how the two nascent populations became physically separated and how they became genetically isolated."
But why should they be separated? I consider evolution to encompass all of that - change in allele frequencies, vicariance events, hybrid swarms, introgression, extinctions, it's all part and parcel of the same story, all related to how populations change. Claiming that micro and macro are different things entirely creates a nasty semantic problem that something is radically different about the way macroevolution works, and plays right into the hands of Creationists. Just because some people have decided to narrowly focus on the allele frequency part doesn't mean they should claim a "different" type of evolution than the people who look at how that interacts with other events on a large time scale. It's like claiming that being a saucier is fundamentally different than being a line cook. The main difference is that one does specifics while the other coordinates several areas at once, but they both need to know what the other is doing, they use mostly the same tools and techniques, and the same product comes out at the end.
Posted by: Carlie | August 21, 2006 10:07 PM
Larry - I did misunderstand your point, although I would argue that the distinction you are making is still somewhat artificial. Asked in the way you have stated above, the answer to the question regarding the basis for the absence of large placental mammals in Australia cannot be answered using population genetics alone.
However, the problem here is separating the idiographic aspects of evolutionary theory from the nomothetic aspects. I would argue that population genetics and mutation are the nomothetic aspects - they can be applied in a unified manner. The idiographic aspects are certainly important, but I would argue that all evolution is ultimately the embedding of universal principles of mutagenesis and population genetics in a set of unique environmental conditions.
In the case of Australia, it is the timing of the breakup of Gondwana combined with the fact that mammals neither fly (with the obvious exception of bats) nor raft successfully across bodies of water. So I agree - understanding both the set of unique individual events and aspects of natural history (vicariance events, physiological limits to dispersal, etc.) are critically important.
Although important at the deep-level in phylogeny, the unique events can also establish subspecific differences while subsequent changes can reverse the separation of populations. A major component of phylogeography is understanding the impact of these historical events upon gene frequencies - so I would argue that the sharp distinction you are drawing is more reflective of fields of study than of biology.
However, the debate in the literature has largely focused on the question of whether there are aspects of macroevolution that are fundamentally distinct from those that characterize microevolution. I would say "no", although I do not count the simple fact that microevolutionary processes are embedded in a larger "parameter space" that reflects the physical environment and species interactions as a reason to assert that there is something "beyond" microevolution. I would argue that the situation is comparable to populations in a genetic algorithm with an enormous and complex parameter space (with multiple and shifting optima) - it should not be surprising that populations can't get anywhere in parameter space (e.g., that placental mammals can't cross to isolated land masses).
Whew.. I would add that the origin of mitochondria can be explained in microevolutionary terms. If a consortium of microbes (e.g., Bill Martin's hydrogen hypothesis or the related syntrophic hypothesis of Moiera) has an advantage of the individual species both members of would experience selection to maintain the consortium. If genetic exchange between the species of microbe was neutral (or advantageous) it could be fixed, despite the fact that it could render the individual species dependent upon the consortium. Once the consortium transitions to a genuine endosymbiotic situation there are well characterized reasons for gene transfer to the nucleus.
This is not to say that there aren't mysteries associated with eukaryotic origins - there certainly are. But I don't think there is anything for which it is obviously impossible to explain in microevolutionary terms.
Posted by: Edward Braun | August 21, 2006 11:09 PM
The micro/macro distinction only works if one believes in biblical "kinds", which are essentialist illusions. As someone else once said, believing in microevolution and not macroevolution is like believing in inches and not in miles.
Posted by: Pete K | August 21, 2006 11:14 PM
"Species" - an organism that can breed with its' own memebers, but not others.....
BUT, as Dawlins, and others have pointed out, this definition, whilst generally useful, falls down sometiomes.
There ia/are the gulls, which live around the N. palearctic region....
Here in England we have the lesser black-backe gull - which can cross-breed with the Siberian lesser bb gull - which can breed with the Heuglins gull - which can breed with the Birula's gull - which can breed with the Vega gull (BTW we've been goin round the Arctic Ocean in ab Easterly direction, and are now at the Bering strait - which can breed with the American Herring gull - which can breed with the (European) Herring gull - which is completely different from, and genetically incompatible with the lesser blackback ...
Dawkins also gives an example in "The Ancestors' Tale" of Salamnders in the USA
Posted by: G. Tingey | August 22, 2006 3:46 AM
I'd love to see PZ further explain his initial comment rejecting the "myth" of macro vs. micro evolution, as from my viewpoint, I tend to agree with Carlie.
All of us in the zoo. dept. at UC Berkeley never found reason to make the distinction, and NOTHING even in the itarweb has a definitive reason to make the distinction.
both "macro" AND "micro" evolution have refered to chaning allele frequencies within a population, depending on who published a given paper. However, they do essentially refer to the same thing.
I've only ever seen the term used by any biologist to temporarily make a distinction for arguments sake, but I've personally never seen a real distinction made in the literature.
Aside from the creobot usage, that is, which is of course of their own design.
It's definetly worthwhile to hash this out, since, as I mentioned, there isn't really any definitive authority on the subject.
which of course bring up an obvious question:
what would one accept as an authority on the validity of seperating the terms from the more parsimonius "evolution" by itself?
Would any recent well accepted and used college level text on evolution be authoritative to most here?
My version of Futuyma is pretty old at this point. Could somebody check and see what a new version of Futuyma has to say on this issue?
if it says nothing, I'd say that's a definitive answer by itself.
Posted by: Ichthyic | August 22, 2006 5:09 AM
The recent burst of evolution in beak size in a Galapagos finch would be microevolution, I guess? But we can't explain that solely with population genetics either, we have to include the change in environment and the competition with another species.
And people (like me) studying microevolutionary events want to know those things, too. Or whatever the equivalent questions are for their system.
Posted by: windy | August 22, 2006 5:34 AM
Tingey,
"Ring species" like your UK gulls are a pertinent dataset for micro/macro-evolution. The gull data have turned out to be even more complex so their status as a ring species is disputed - see the Liebers citation provided by the wikipedia on ring species. But Wake's salamander study and Irwin's greenish warblers are canonical, and Irwin's site has a .pdf of his 2001 Genetica article discussing the micro/macroevolution issues explicitly from his perspective.
Posted by: thwaite | August 22, 2006 11:55 AM
windy and Pete - I obviously agree with you regarding the big picture: macroevolution does not involve any fundamentally distinct processes from microevolution.
But I think there is a way to reconcile this position with the position advanced by Larry. The analogy I would use is chess. There is a limited set of moves that are straightforward to learn. So, if you wanted to study chess at a "micro" level all you might need to understand is the simple set of rules. But understanding a whole game would require understanding more than the rules - you would need to know the history of how that specific game unfolded.
When does understanding the history of a specific game become vital to understanding what is going on? I suppose it would depend on exactly what you wish to learn and what is going on.
I would argue that studying microevolution allows the use of certain simplifying models. For example, you don't need to know when New Zealand separated from Antarctica to study the distribution of genotypes in a North American bird species. But when do you need to start understanding the idiosyncratic historical details of the environment? There is no clean answer - you might have to consider Plio-Pleistocene climatic fluctuations to understand the present day distribution of genotypes in that North American bird species.
The point being that for certain questions focusing only on allele frequencies is sufficient, and those questions tend to involve a relatively shallow history. But that is - in my mind - simply a question of what we need to know to study a problem. The idiosyncratic historical details always matter - but we sometimes look at questions where those idiosyncratic details do not contribute significantly to variation in the character being measured.
I would argue that everything I described is consistent with macroevolution being the accumulation microevolutionary changes (in the context of all of the detailed issues discussed). The danger in my mind of saying that macroevolution cannot be explained by microevolution is that it may imply that something we haven't seen yet (e.g., the hand of the designer) is needed to allow evolution to proceed past a cetain point. I don't think any of us believe that! (well, the trolls don't, but this discussion probably isn't interesting for trolls)
Posted by: Edward Braun | August 22, 2006 11:59 AM
Okay, since someone asked, I perused some evolution textbooks for definitions of micro- and macroevolution. Unfortunately, I've misplaced my copy of the most recent Futyuma, so my sources are older but all were essentially the same: Microevolution refers to changes in gene frequencies or heritable traits within populations and species, while macroevolution represents changes among populations or species that may lead to classification into higher-level taxa.
Posted by: cserpent | August 22, 2006 12:12 PM
I agree that you have to go beyond population genetics to explain the origin of new populations from older ones, and to explain the extinction of populations. But I would add that characterizing microevolution as just population genetics is a strawman argument. Population genetics is a set of tools that can be used to infer evolution, but shouldn't be confused with the evolutionary processes it infers.
Speciation usually (polyploidy being an obvious exception) is not a singular event. It occurs as many small events over time and space. Natural selection and allopatry together can explain some, perhaps most speciation events. Higher order diversification is just a continuation of the lower order events across a broader sample. Just because large numbers of species are affected by large-scale events doesn't mean that you can't reduce the picture to individual populations consisting of individual organisms coping with local consequences of those global events.
Posted by: cserpent | August 22, 2006 12:15 PM
Whoops, my bad: Irwin doesn't discuss micro/macroevolution as such, only microevolution and speciation. Though from his perspective of a few years studying subspeciation, full speciation may look pretty macro...
Posted by: thwaite | August 22, 2006 12:23 PM
I would like to see Larry address this. I think it is now pretty well established that his first attempt to draw a fundamental conceptual distinction between micro- and macroevolution didn't fly. Can he do better if he has another crack at it?
Posted by: Steve LaBonne | August 22, 2006 12:36 PM
Yes and every chess game is unique, just like every biosphere's evolutionary history must be unique. As chess can can be played with strategically, we can ask whether there are discernable "strategies" in macroevolution, whereby evolution exploits possibilities in ever more interesting ways (e.g. the so-called major macroevoltionary transitions such as eusociality, multicellularity, intelligence, impetus towards overall increased complexity)?
Posted by: Pete K | August 22, 2006 1:11 PM
Steve LaBonne says,
I'm sorry that my little essay didn't do a very good job of summarizing the opinions of many evolutionary biologists. However, I did include lots of references so you can read the primary works if you want.
I'm not going to take another crack at it. I'm happy to let the following scientists have their turn ...
Francisco J. Ayala
R.I. Carrol
Niles Eldredge
Douglas H. Erwin
Eugenie C. Scott
George C. Williams
Steven M. Stanley
Stephen J. Gould
Philip Kitcher
Ernst Mayr
Jeffrey S. Levinton
Mark Ridley
Bruce S.