South Carolina State Sen. Mike Fair is doing his usual creationist thing and trying to block the teaching of evolution in public schools. He’s wrong. He’s an idiot. But then I read the clause in the state science standards that he’s opposing.
Conceptual Understanding: Biological evolution occurs primarily when natural selection acts on the genetic variation in a population and changes the distribution of traits in that population over multiple generations.
Performance Indicators: Students who can demonstrate this understanding can:
Analyze and interpret data, using the principles of natural selection, to make predictions about the long term biological changes that occur within two populations of the same species that become geographically isolated from one another.
Wrong, wrong, wrong. Fair’s argument is that this is Darwinism
, and Darwinism
must be opposed. My argument is that this is wrong because it equates evolution and natural selection, and even makes a factually incorrect assertion, that evolution is primarily a consequence of natural selection.
What’s a guy supposed to do when both sides of the debate have screwed up so thoroughly? Fair is more wrong, but I’m not in favor of teaching kids false versions of biology, either.
what, does Larry Moran owe you money or something?
ah hahah ChasCPeterson.
I was going to say, the conceptual mistake in the standard is real, but most educated evolution-accepting adults are never going to understand the distinction. Yeah, both are technically wrong, but when you say that Fair is “more wrong”, that’s the understatement of the year…
Write to the people who wrote the standards and tell them why it’s wrong.
This may have the enjoyable side-effect of Senator Fair crowing when they withdraw it, then exploding with frothing, uncontrollable rage when a more rigorous version is published.
Okay, so what am i missing? (Apart from a formal education in the biological sciences.)
I know (a little) about random mutations, the founder effect, & genetic drift. Aren’t they what natural selection acts upon? If so, it looks to me as though evolution is primarily a consequence of natural selection.
When it comes to making predictions about long-term biological changes, i would have thought that there are too many variables for us to do that, outside of laboratory conditions, with bacteria.
That holds for science education in general. I remember having extreme difficulty un-learning shit like the “hypothesis -> theory -> law” progression that I was taught in third grade. I never got even the slightest indication that it was wrong until my sophomore year at college.
How is evolution NOT a result of natural selection? Isn’t that exactly what Darwin taught? I am completely surprised and confused now.
You have to start with the basics.
Im a little confused. I understand the first problem I think, that evolution is a fact and natural selection is the explanation for it. The second problem is that you cannot predict how an organism will change using natural selection because its impossible, or at least very difficult, to guess what mutations, how the environment will change, etc
*Meekly raises hand*
I was under the (evidently mistaken) impression that, in nature, evolution is the primarily driven by natural selection?
Just to throw a little more wood on the Mike Fair is an asshole fire, not only is he a creationist but he also opposes allowing Craft breweries in SC selling pints to customers on for on premise consumption.
Been pushing creationism based education in SC for a long time AND he’s fucking with beer?
Yeah. Fuck that guy.
Is the wrongness because they missed out the vital element of random mutation? (I thought that was what they meant by “genetic variation”, though – presumably they used incorrect terminology if that was what they meant???).
I’m waiting for PZ to explain hisself here, but if he doesn’t do so soon I’m going to have to do it myself…and nobody wants that.
Help.
Can someone PLEASE PLEASE PLEASE suggest best books to clarify the whole evolution / selection / drift / etc etc etc?
Wanting something “introductory,” by which I DO NOT mean “written for idiots looking for party factoids.”
Thank you.
ChasCPeterson’s explanation was the closest: It turns out that Larry Moran was behind the DDOS attack, and he is holding FtB hostage unless PZ agrees to slam overly adaptationist perspectives at every possible opportunity :p
That is an asshole move.
If you’ve never been to a wedding reception at a craft brewery and toasted the bride/groom/whoever’s speeching at the moment with a freshly drawn pint, you’ve not lived.
Random processes like genetic drift. Geographically-isolated populations will diverge and speciate even without any natural selection pressure, due to random changes in frequencies of alleles that don’t affect survivorship. The “founder effect” is a dramatic example.
Most evolution is neutral or non-adaptive. There is a constant churn of nucleotide changes in the genome. Many of them will be phenotypically neutral — synonymous changes in codons, for instance (although there are cases where codon frequency makes a difference). A subset of those changes will have phenotypic effects, and most of those will also have no significant effect on fitness. Another subset — a fraction of a fraction — will have effects that do expose the individuals bearing them to selection. So in general, selective changes will be the minority of variation in a population. Those changes are the engine of adaptive change so many people think they’re the only important ones (they’re wrong), but if you’re talking about the raw quantity of genetic change, neutral evolution rules.
As for books: Zimmer’s is a good popular read. Futuyma’s textbook is still more or less the standard.
#14, jamessweet:
Sorry, doesn’t work. I’ve been slamming adaptationism for years, even before I got to know Larry. He knows he doesn’t have to extort me to get me on the righteous side (he might occasionally poke me for being insufficiently dedicated, though).
#10, Rev BDC:
He’s anti-beer? May he rot in hell.
Oh, come on, Chas. You know this sentence, , is simply wrong. Change to “Adaptation”, and I’d have accepted it as a fair simplification, but as written, it’s just totally false.
Well, I’m a bit surprised at the comments. Apparently Larry Moran was right, and most people have no idea about the prevalence of neutral evolution. But I can see why. Who writes popular books on the glories of drift? All the cool stuff — flight, big sharp teeth, fancy ornaments, tool use, etc. — is selection. All the science blogs are full of bizarre adaptations, but seldom a word about the boring, pointless bulk of fixations. Junk DNA just isn’t as much fun, even for many biologists, which is why so many are trying to kill it off.
Now, I seem to recall that you have posted on the subject of neutral evolution before. But judging by the comments, perhaps it’s time for another.
As for books, is Li & Graur’s Fundamentals of Molecular Evolution too dry and technical?
To people who don’t even know about drift yet? Yes, Li & Graur is way too overwhelming. Let’s hit ’em with Koonin’s Logic of Chance instead. Or Lynch’s Origin of Genome Architecture. (JUST KIDDING PEOPLE. DON’T TRY THESE IF YOU AREN’T FAMILIAR WITH BASIC EVOLUTIONARY CONCEPTS. We’ll scare you straight into the simple-minded arms of creationism.)
The only “predictions” I hear attributed to Evolution is the advice, “when prescribed anti-biotics; take the full prescription, don’t stop halfway”; that only taking the dosage for half as long will breed “resistant” bacteria. And this has actually happened. What is not mentioned by that; is that evolution occurs all the time, ‘natural selection’ doesn’t always eliminate one variant from the others, but only increases its survival *rate* over the others. I think The “State’s Standard” is not *totally* wrong, just focuses on a single detail of the subject and disregards all the rest of it. Evolution in a *complex* subject. [but that is just my simple, engineering, mind talking, don’t understand all of evolution in the slightest]
Plus, natural selection is not even the only kind of selection. There’s kin selection and sexual selection for starters, and one can argue whether predator/prey interactions fall under the natural umbrella.
I always thought that “natural selection” was a paraphyletic term… And Koonin is going on the wishlist. That looks like a fascinating read.
carlie: both kin selection and sexual selection are forms of natural selection, so that isn’t a problem. Nobody would argue that predator/prey interactions don’t fall under the natural umbrella, so that isn’t a problem either.
No, the problem is that the standards assume that “natural selection” and “evolution” are synonyms, and most of what they forget can be subsumed under the label of drift. I would also argue for the potential importance of macroevolutionary processes that don’t easily fit into what they said either, e.g. species selection.
I’m also confused and will like to be less ignorant (have a huge burden of catholic education to overcome even being 32 years old and always interested in science).
Coming from engineering fields and not being English my first language, it’s easy for me to understand in terms of equations.
So this will be correct? (or less ignorant :P) :
Genes = phenotypically neutral + phenotypically active
with phenotypically active << phenotypically neutral
<<: much less (1 percent?, less?)
And also:
Genes subject to natural selection << phenotypically active
Abbreviating:
[1] G = PN + PA = PN + PA_NS + PA_S
[2] PA_S << PA_NS << PN
G: genes
PN: phenotypically neutral
PA: phenotypically active
PA_NS: phenotypically active not subject to natural selection (not selected:NS)
PA_S: phenotypically active subject to natural selection (selected:S)
Then we have evolution which I put like a function e(),
Applying to [1]:
[3] e(G) = e(PN) + e(PA_NS) + e(PA_S)
And also natural selection ns().:
ns(G) = ns(PN) + ns(PA_NS) + ns(PA_S)
but ns() has no effect on PN and PA_NS, only in ns(PA_S):
ns(PN) = 0 and ns(PA_NS) = 0
then
[4] ns(G) = ns(PA_S)
Combining [3] and [4]:
e(G) = e(PN) + e(PA_NS) + ns(PA_S) (*)
Where it's visible than evolution is a much bigger process than natural selection.
Is that conceptually acceptable?
(*): yup, I know that I should have used e(PA_S) = some_function( ns(PA_S) ); but preferred not to obscure the equation.
…meeeh.
Look, I appreciate rigor and exactness. For Euler’s sake, I’m a mathematician. But if one high school student is explaining to another that x^2 + y^2 is not the same thing as x^2 + 2xy + y^2, I’m not going to horn in with “as long as you’re not working over a field of characteristic 2.”
If you really insist on the inclusion of genetic drift and neutral changes in the grade-school curriculum — I agree that it’s not too terribly difficult a concept — I’d point out that the standard does mention “the genetic variation in a population.” So where does that come from? The constant, neutral churn that you describe. So it’s implicitly there, at least.
What is the motivating question that evolution answers, especially from a student’s point of view? I’d say it answers the question “Where did all these species come from?” and the answer is, “they diverged from common root stock.” So the relevant phenomenon is, in fact, changes — phenotypically active genetic differences that become differently distributed in different populations.
Natural selection is not the be-all and end-all of evolution. Granted. It’s a perfectly good starting point, though.
Gee, go figure SC (my state), the only state in the union that the web site LessWrong just fucking gave up on. Something along the lines as “it is a physical impossibility to make the state “”less wrong ! “”.”….. with a logically complete proof that followed.
sigh….. why do I even have a desire to live anymore.
On the upside, we are the only state to offer any verifiable proof that “only the good die young”……e.g. ” Strom Thermond”.
Ehhhh, I think I have to agree with johnharshman #20. I understand why PZ might get exercised over having to make his freshmen students unlearn a bunch of stuff every year, but with 40+% of Americans thinking species are created by magic, I think it would be just fine if they came to understand evolution only about as well as Darwin did.
Thanks for the book-learnin’. Now please provide one (1) documented example of the founder effect causing speciation due to drift alone.
Lurkers: you probably don’t need a textbook to follow this argument along, but you do need sufficient background information to unpack this blithe statement of Fact.
First, the definition of ‘evolution’ employed is the (conventional) maximally reductionist one from population genetics: A change in allele frquencies in a populaiton’s gene pool.
Next, we immediately turn our back on the population-genetics definition of ‘allele’ (basically a symbol in an algebraic model) and adopt instead one from molecular biology: raw nucleotide sequences in DNA.
And we’re pretty much done. Most changes in DNA nucleotide sequences are in junk areas, or at redundant positions of codons, etc., so voila! Most evolution is drift.
All that’s left to do now is to extrapolate your hermetic knowledge staight to phenotypes (what? never mind!) and then go about waving your dog-eared copy of Saint Gould while sneering at people who actually study organisms for underestimating the pre-eminent importance of random drift, the fools.
You can back that one up with data, right? Not a statement of faith at all. Right?
Sure, I know it’s “wrong” given the assumptions of Correct Definitions outlined above.
But if we assume from use of the word “traits” that we’re actually talking about phenotypic evolution instead, as might be appropriate at the High School Biology I level, then it’s not so wrong.
Correct.
Which is why the very best, most effective way to turn off young students on the whole subject of evolutionary biology is to start them right off with Hardy-Weinberg Equilibrium and the abstractions of population genetics. As pretty much all the textbooks, and therefore course, do.
Both best considered subsets of natural selection writ large.
uh
wut
lol, do you have any examples of ANY single force of evolution causing speciation all on its own? what would the criteria for that even BE?
* ah, perhaps chas thinks PZ claims the event has occured. i read it as if PZ was saying it would be possible…
1. Even being swallowed by a whale and susequently regurgitated alive could not scare me back into the arms of creationsim. But my experience says that it’s a valid warning in general, regarding the mass of humanity that holds “if I don’t already understand it it’s crap” as a valid intellectual scaffolding.
2. Speaking of which, adaptationism was just mentioned, and I had to go do some reading, because ignorance. After an hour or so it became clear that the issues point to finer points than are initially obvious… but because I have spent a LOT of time VERY close to committed creationists, I have to say this: If you want to start a small scale spitting contest with a creationist, mention adaptationism.
This is a vain prediction really, because I’m not sure how anyone would engage most creationists long enough to get past much simpler shouting points. But if you did, and they were to spend the typical creationist maximum of 10 minutes research on the concept, they’d almost certainly hit on the term “optimal,” and from there it would be “OPTIMAL! THEY SAID OPTIMAL! NOTHING RANDOM CAN BE OPTIMAL! OPTIMIZATION IMPLIES DESIGN! THEY’RE SUPPORTING INTELLIGENT DESIGN, BUT THEY HATE GOD!” Or something like that.
*makes popcorn for everyone!*
What, group selection?
*prepares for holy war by waking & fasting*
It would have been nice if the science standard had been more accurate, but at least it would put Evolution out there. Having grown up in SC, I only got exposed to Evolution, formally, when I was a senior. In an AP Biology class, and that was still was with some controversy in the class. Not from the teacher, mind you. She was serious about it.
The sad truth is that no matter how well the standard is written, there’s still a number of teachers that would utterly fail at teaching Evolution in those classrooms. Which is a pressing problem as well. Even if this flawed, or a more accurate standard, were to pass, there’s still a number of teachers that would fail to do their job correct by their own initiative.
Don’t get me wrong, having the standard pass, even as flawed as this version is, would be a vast improvement. However even getting idiots like Fair out of the way will only be the first step.
Don’t overlook this:
No meaningful “long term” prediction is possible. For all we know, an ice age wipes one of the populations out. Or a drought. Or warming. If two populations of temperate foxes move, one to a colder climate and one to a warmer, I’m guessing they want us to predict that one will get shaggier and one will get less shaggy. Which is a decent guess. But one might go bald, and the other might also go bald but evolve a larger body mass and faster metabolism. Or something resembling feathers, for that matter.
The idea that evolution is predictable entails the idea that it’s deterministic, which is only a step away from the idea that it’s a goal-directed process of “improvement.”
@ PZ #17
Ah, cool. Thanks for the clarification, PZ!
Yes, evolution is not just about adaptations which are primarily driven by selection. But there is lots of other non-adaptive stuff going on, drift, gene flow, self-organization etc etc which influences evolution.
I may be mistaken but last I heard the validity of the neutral theory has not been entirely settled at least according to the Ridley Evolution text I happen to have. I stand corrected if I am wrong.
But the creationist is still more wrong that the state clause which he would be apposed to even if it were properly expressed in a more nuanced and correct manner.
saying most genetic change is neutral has nothing to do with whether selection is a driving force in the EVOLUTION of any given population. Even Kimura didn’t actually have any evidence to suggest drift was the primary way evolution occurs.
PZ, you’ve gone way around the bend on the anti-selectionist bias these days.
there is not enough evidence to suggest that for ALL populations, drift is more important that selection for fixing genotypes.
the ONLY groups it’s even been looked at extensively are microbial FFS.
this is a really naive argument to be making here, and I’d be shocked if this is how you actually teach it.
Ok, the wording is a bit off but I doubt that precludes getting an understanding of the basic concept.
Usually these sorts of bullet point targets are meant to work in conjunction with one another. There should be another one right next door that talks about mutation and so forth. I wonder if there is.
That would be more concerning, actually: if this were the only bit of the curriculum that annoys a creationist.
…frankly, my guess is that the question will never be sufficiently answered, because by the time you fully examine any given population over time, the relative strengths of drift and selection would likely have changed before you even finish the study.
let alone for ALL populations.
to argue the nuance for a science standard for the secondary school level is ridiculous. for the undegrad, it becomes far more important, for the grad and post grad, this is of course meat and potatoes.
but it’s a ridiculous argument to make at this level, ESPECIALLY when measured up against the kinds of attacks that are actually being thrown at the science standards by the likes of Mike Fair.
So anything that happens in nature is natural selection? That’s almost as sloppy as using the term “organic”; it becomes basically meaningless. It’s more clear to use natural selection for environmental pressures and use different names for organismal interactions. At the broader level it’s all “natural”, but that isn’t a very informative way to look at it.
GO SIT IN THE CORNER RIGHT NOW AND THINK ABOUT WHAT YOU’VE DONE.
My opinion doesn’t matter, but I agree. If we go down that road, then “artificial” selection is also natural, because humans are products of nature, and their breeding prettier puppies is no different, really, than peahens picking the prettiest peacock. (Groaning at my own alliteration.)
My curiosity piqued, I had a look. And indeed the previous section to the one the senator complains about is all about the ways in which DNA can change, from sexual to mutation etc.
This is just the outline as well. If the senator really has a problem you’d think it would have come up before now, since the 2008 actual working guidelines are loaded with natural selection and genetic variation stuff and the new one seems targeted to repeat this.
So, yeah the wording might not be perfect at that precise point, but if all went to plan, by the time a class got to natural selection and speciation they would have covered quite thoroughly the most well known ways that DNA can change. How natural selection acts on a population with variety and where that variety comes from would be fairly unmissable I’d think. That is the goal for the course structure by the looks
Short version: the senator is an idiot and jumping on a single phrase he knows is a dog whistle, regardless of what the remainder of the document actually says, or how the extant curriculum actually works (but we knew that) and I wouldn’t hang this document on a few words for being the short version you show to politicians.
Chas & Ichthyic, 2 questions.
1. Define evolution. Waving your hands and saying “this isn’t real evolution” to discount molecular genomics isn’t very helpful.
2. Explain how molecular clocks work if selection is all that matters.
Ichthyic:
You are right, though your claim is garbled. The evidence favoring the prevalence of drift is the percentage of junk DNA in most eukaryote genomes; drift is the only way in which junk DNA evolves. In humans, therefore, almost all fixations must be neutral, since most sites have no effect on phenotype. Most prokaryotes have very little junk, so drift would be a less important factor there. But I still bet that even in prokaryotes most evolution is neutral, and it’s easy to test that by comparing the number of silent substitutions vs. the number of replacement substitutions.
carlie:
No. How could you possibly get that from what I said. However, any differential reproductive success correlated with genotype is most certainly natural selection, and everything you have mentioned so far is just that.
See, that is where I disagree with you. “Natural selection” is so broad of a term, then, that it carries almost no meaning. And why are you completely discounting neutral changes and drift?
Besides which, when you try to just classify all types of selection as “natural selection”, you run right into the problem of contradictory selective forces, which is where sexual selection was noticed to begin with. You get hopelessly semantically confused if, to use the most classic example, you have to say that natural selection in a particular population favors shorter peacock tails but natural selection also favors longer peacock tails in that same population. It’s like trying to force people talking about mammals and insects to collapse it all down into calling them all eukaryotes. At some level it is technically true, but it isn’t at all useful at the level of detail you need when you’re talking about what’s actually happening evolutionarily within the group.
You know, a single word fixes those standards. Just stick “Adaptive” in front of “biological” as the first word. I would not be surprised if almost everything that’s actually in the textbook and the curriculum is adaptive evolution anyways. The neutral theory is mostly university level stuff.
So close. You almost have it.
1. Evolution the fact is that life changes through time. Evolution the theory is how and why it does. This encloses both so called natural and artificial selection.
2. There really isn’t any difference between artificial and natural selection. Life changes through time in both. And it is silly to claim humans aren’t natural. As 1/2 of the large animal biomass on the planet (with much of the rest being cow), and 7 billion of us, we have a gigantic impact on the biosphere. Much of it not good according to common but not universally held values.
3. The difference between artificial and natural selection is…artificial. My impression is that a lot of biologists are trying to get away from this false dichotomy or just ignoring it all together. I’m one of them.
“The neutral theory is mostly university level stuff.”
As an AP Bio teacher in PA, I must admit that you’re correct…the majority of us teach adaptive evolution, as per the textbooks (Campbell, et.al.). Thanks to PZ’s post – and my respect for Larry Moran’s blog – I feel admonished, and will attempt to raise awareness with regards to the “random” effects of genetic drift.
Molecular genomics must be addressed when studying evolution.
Cthulhu yes.
You want to try to get one or two basic concepts fixed in secondary school. The mountain of details are for majors and postgrads.
1. Evolution happened. The dinosaurs were real, they are gone, exept for the avian clade which is hanging around the bird feeders trying to fight off the squirrels.
2. E = RM + NS. It’s more complicated than that but you need to understand the basics first.
Think this is simple? Almost half the US population thinks some magic sky fairy did it while 20% thinks the sun orbits the earth and can’t diagram the solar system, a task I learned in the first grade.
I only have a layman’s understanding at best, but I’d always thought “natural selection” was an umbrella term for all of the undirected selective pressures on a population; in opposition to “artificial selection”, or selective breeding, which involves deliberate pressures directed by agency with intent to achieve a specific outcome.
So yes, there will be competing pressures from different factors, but surely that’s true regardless how narrow you want to focus. The peacock’s tail might be a positive for sexual selection but a negative for predation selection (I’m guessing); but every trait must also, at a minimum, be a balance between whatever selective advantage it confers, and the energy expenditure necessary to produce it.
I imagine selective pressures as a bunch of vectors on a point. They might point all over the place, but when you add them all together the result might point up (advantage), down (disadvantage), sideways or be negligible (neutral). Collectively, all those vectors describe natural selection.
If someone comes along and starts adding new vectors and removing existing ones, they could steer the point to the right… and the sum of those changes would be artificial selection, because there is a goal in mind.
Evolution: Life changes through time.
or selective breeding, which involves deliberate pressures directed by agency with intent to achieve a specific outcome. The end result is life changing through time. This is evolution.
One more time and it is late here and I’m done for tonight.
1. In the lab you take Mediterranean fruitflies and treat them with a pesticide. You derive a resistant mutant. Artificial selection.
2. Some farmer finds Mediterranean fruitflies in an orange grove. Planes spray 200,000 acres with the same pesticide. A few years later, someone finds more, and they are resistant to the pesticide. Natural selection.
What is the difference here? In both cases you have the exact same result, pesticide resistant flies, that evolved. It really isn’t a useful distinction, especially since our effects on the biosphere are gigantic. It’s all evolution and we are just a main part of the current environment.
Carlie:
I don’t understand your point at all. “Natural selection” carries a simple, clear meaning, which is differential reproduction correlated with genotype. Drift is not correlated with genotype and isn’t natural selection. But saying that drift isn’t selection doesn’t discount it at all.
You don’t need sexual selection to get contradictory forces. The selection on an allele or individual can be the sum of many competing factors; the technical term is “tradeoffs”. Sexual selection is just natural selection focused on mate choice. Selection can also focus on life history traits, predator avoidance, feeding strategy, and a host of other things, many of which can push in opposite directions. And it can be interesting to consider all these factors separately, and even to give selection based on them their own names. Still natural selection, though. The distinction is artificial.
39 Ichthyic
I’m confused, and I don’t know if I can state this clearly. If I just need to go read more, say so. That may well be the only valid response.
But if I understand correctly:
– Evolution occurs whenever there is a heritable change in the genome, and genetic drift alone can cause a single population, when separated into two groups, to become two distinct populations IN THE ABSENCE OF SELECTIVE PRESSURE.
– Some (most?) heritable changes in the genome have no effect on phenotype, so there can be no adaptation as a result of those specific changes. But the persistence of these changes are still results of evolution.
– So… if changes that can’t be acted upon by selective pressure are evolution, and if evolution can occur in the absence of selective pressure, what is the specific meaning of the term “driving force” with relation to evolution due to selection (adaptation?), and in the statement above, what is the difference between phenotypically neutral heritable change (which is evolution), and selected heritable change that is being emphasized by the use of capitalization?
– I know I’m missing something, because it SOUNDS like one is more “evolutiony” than the other, which seems to imply purpose, which I know isn’t present in evolution.
Perhaps there is good news, PZ:
http://www.charlestoncitypaper.com/TheBattery/archives/2014/02/13/sc-sen-mike-fair-drops-opposition-to-evolution-teaching-standards
So feel free to fulminate at sloppy wording.
Except that that’s wrong no matter how many times you say it. You would have to reword it to say “differential reproduction as a result of environmental influences on traits controlled by genotypes”. What you wrote doesn’t make any sense – differential reproduction can result from many things, not just natural selection (which is what we’ve been saying all along here), and correlation doesn’t mean anything.
It absolutely is correlated with genotype, or it wouldn’t be detectable. It’s just not caused by genotype. You’re confusing correlation and causation. And of course it isn’t selection, it’s drift!
#49, Amphiox:
That’s what I said, way back in #19.
@carlie
the solution to that problem is to, i dunno, invent a term like “ENVIRONMENTAL SELECTION”.
just like we don’t throw out the word “eukaryotes”, or decide that, really, only insects should be called “eukaryotes”, so too is it silly to use a very general phrase with well-established meaning for the kind of particular articulation you are asking for.
insects and mammals are a subset of eukaryotes. and sexual selection and evironmental selection are a subset of natural selection.
it’s simple.
my two cents…
Except that natural selection as originally described didn’t encompass things like sexual selection. Darwin’s definition was limited to environmental influences. That’s why they came up separately. It’s not the word’s fault that people got overly broad with it.
Fair enough. It does seem to me that you’re bucking a century of common usage, though, where “natural selection” was originally coined as analogous to, but distinct from, selective breeding, and has since been used as an antonym of selective breeding, which is commonly called “artificial selection.”
The distinction seems useful to me. Technically, my laptop is a natural phenomenon–but we use the word “artificial” for that subset of natural phenomena that were produced by humans (or in sci-fi, by other intelligent species). Useful despite the contradiction that we don’t call birds’ nests “artificial.”
…and yet you’re obviously right, Raven, in that there’s also a continuum of “artificialness.”
It seems apparent that we “bred” wild animals to fear humans, by slaughtering the ones that came too close, which is why American megafauna and dodo birds were quickly hunted to extinction. So was it “artificial selection” that produced the phenomenon that “the fear of you and the dread of you shall be upon all the beasts of the Earth,” as Genesis inaccurately puts it? I’ve never heard it described that way, but it’s as human-caused as the domestication of dogs or the breeding of racing pigeons.
I agree that there is a very useful difference between artificial and natural selection. Natural selection, as we drill into students over and over, does not have a goal. It is reactionary to the conditions of the previous generation. It is not working towards anything. Artificial selection, however, is done by people with a particular goal in mind. It is working towards something. Putting them both together blurs that line back into anthropomorphizing nature into striving towards perfection through evolution.
Carlie,
Now you’re just getting crazy. Drift is differential reproduction uncorrelated with genotype. That is, we can’t predict based on genotype whether an individual is expected to have greater or lesser reproductive success. With selection, we can. And “correlated” is another word you seem to think has no meaning, when a trip to the dictionary might argue otherwise.
As for sexual selection not fitting the original definition of natural selection, why would you imagine that other individuals of your species are not part of your environment?
Phenomena like this is when I started to wonder if the artificial selection term was worth it. There are a lot of cases where it is hard to decide if something is natural selection or artificial selection.
1. It’s not clear that we domesticated a lot of our animals deliberarely. Or at all. They might have domesticated themselves by adapting to humans. It’s been a successful strategy for dogs, cats, and cows. There are a few hundred thousand wolves and an estimated 400 million dogs. The ancestor of the cow, the auroch is extinct but cows are everywhere.
2. Same with our domesticated plants. What the ancient pimordial farmers were thinking is lost in time. But plant domestication may well just follow from the process of agriculture, early on at least.
You could just subsume all this under the term “environmental selection”.
But at any rate, “natural selection” is so deeply embedded as a term that it won’t go away.
You seem to entirely not understand what “correlation” means. Here’s an example of drift by founder effect:
100 individuals with blue eyes and 5 with brown live on an island. A boat comes by. By crazy random happenstance, 4 of the brown eyed individuals hop on the boat and get carried to another island and start a new population. You couldn’t predict which ones would be right next to the shore when the boat sailed by, but that’s what happened, and the next generation on the new island will be predominantly brown-eyed.
In this case, the genotype of brown eyes is absolutely correlated with reproductive success on the new island. It simply isn’t causal.
I’m not saying that they aren’t, I’m saying that sexual selection quite often selects for traits in a completely opposite way than environmental selection would, so it’s needlessly confusing to try to lump them both together.
Carlie,
You seem not to understand what “correlation” means. No, the reproductive success of individuals on the island was not correlated with their having brown eyes. If blue-eyed individuals had happened to jump on the boat, they would have been just as successful. That means there’s no correlation between genotype and success. But never mind that. If you don’t like the word “correlation”, I would be happy to substitute something like “depending”. The point is to have language that means certain alleles or individuals are expected, before considering chance events, to be better at reproducing than others. And that’s natural selection. Fluctuations due to chance are not natural selection.
Again, the fact that some aspects of the environment can push traits in opposite directions is by no means limited to sexual selection. There isn’t a distinction between mating success (sexual selection) and environmental influences (which is of course everything) any more than there is a distinction between feeding strategy and environment or between predator avoidance and environment. Or rather, there is a distinction, but it isn’t a unique distinction; it’s just that we can divide up environmental factors in many different ways, and your dichotomy is no better or worse than many others. We can separate out particular influences if we want to highlight them, but you should realize there’s no difference between separating out mating success and separating out other environmental factors. In any case, different environmental factors can push traits in opposite directions, and the fitness of an organism or allele is the sum of all competing factors.
I didn’t make the claim (neither, btw, did PZ…I was responding to Chelydra).
More clear to you, maybe, but not the conventional meanings of the terms. Where are you getting this stuff? Are you not familiar with the term ‘biotic environment’?
Fortunately for me, I didn’t discount molecular genetics. I even acknowledged your definition and conclusion at the level of molecular genetics.
My point was that molecular genetics is not =Biology, and that evolution can be fruitfully studied at other levels of organization, and that at these other, legitimate levels of study, the statement “most evolution is neutral or non-adaptive” is highly questionable at best.
And, further, these other levels is what nearly all people who aren’t biologists, including highschool students, have in mind when talking about evolution.
But, OK: ‘Evolution is heritable change in populations over time’. There’s a definition you can apply to your wonky sequence information and the rest of us can use to talk about organisms.
I’m talking about pluralism, you’re advocating molecular hegemony.
on account of they are molecular clocks, and as I have acknowledged, evolution at the molecular level is poorly constrained by selection.
(I don’t appreciate you mauling what I actually said into “selection is all that matters”.)
Speak for yourself. There is nothing particularly confusing about the concepts of trade-offs or opposing selection pressures, or stabilizing selection, etc.
The concept is “components of fitness”. Total Darwinian fitness can be conceptually partitioned into components like survival and fecundity. Sexual selection refers to the component of mating success. It’s just part of the whole, but an interesting enough part to sometimes winnow out and examine separately.
(which is, of course, perfectly appropriate for some discussions)
It’s sort of wrong, but not for the reasons you seem to think.
(Natural) Selection is = ‘nonrandom differential reproduction’, with the ‘nonrandom’ referring to both phenotype (not genotype) and the environmental context. Given an environment, differential reproduction of a certain phenotype is (natural) selection, whether it be due to competition ability, disease resistance, clutch size, running speed, coloration, sexy tailfeathers, or whatever. You can look at a particular phenotype and ferret out the component(s) of fitness it is correlated with.
Selection is phenoptypic. The genetic basis of the phenotype in question determines the evolutionary response to selection (if any), and the evolutionary response is contingent on pleiotrpy, epistasis, plasticity, etc. etc.
It’s complicated, of course.
You are a nut. The biotic environment. Competition. Predation. Parasitism. All part and parcel of Darwin’s thinking. As for sexual selection, he pulled that out because he needed it to explain sexual dimorphism, but it’s just another component of fitness (mating success).
@69
ChasCPeterson
ya i kind of noted that i misread what you were saying.
#69, Chas:
Molecular genetics is biology, just as biology is chemistry. Agreed that we can study it at higher levels — really, most of the work on my lab is on phenotypic-level effects of the environment on developing organisms — but you still have to acknowledge that the engines of change are all molecular.
I’d also say that even if you pretend genes and molecules don’t exist, it’s still probably true that most evolution at the morphological level is neutral. Look at nose shapes in humans, for instance: there’s a core functionality that is a constraint, and there are extremes that are going to face negative sexual selection, but most of the variation we see isn’t going to be having a significant effect on reproductive fitness.
You might also look at “Morphological variation in the limbs of Taricha granulosa“, by Shubin, Wake, and Crawford, in Evolution 49(5). It’s a great example of the degree of variation (in this case, in wrist bone architecture) that exists in natural populations. Are we really going to argue that it all has adaptive significance?
There is some controversy over this point, and biologists disagree. Some would say that differential reproduction based on non-genetic characters isn’t natural selection, and some would say merely that it isn’t evolution, and that evolution consists in response to selection rather than selection itself. You apparently go with the second camp, while I would go with the first.
…Evolution is descent with heritable modification. What do you mean instead? Descent with heritable modification of the phenotype maybe?
:-D :-D :-D :-D :-D Day saved!!!
Evolution: Descent with heritable modification.
Cows? Seriously?
Cats, OK; dogs, imaginable; cattle?!?
Au(e)rochs. There’s ox in there. (The spelling is more complex because the word has been sent through the High German Consonant Shift and back.)
There is, it just wasn’t predictable because it’s not causal.
OK, community ecology is just chemsitry.
In the same sense that most evolution is neutral.
Neither truth is of much use to a community ecologist, though.
Nose shapes and newt wrists: Sure, ‘traits’ that exhibit lots of variation within populations are evidently not subject to selection; within constraints one nose or wrist might be as good as another. (Of course, there is considerable geographically correlated variation in human nose-shape on top of the within-population variation, but that way lies the horrifying spectre of Scientific Racism so we’ll pretend not to notice.)
Thanks for the link to the Shubin et al. paper; I hadn’t seen it and it’s interesting work for sure. I note that they found a perhaps surprising amount but a limited range of such variation; it’s not like any old bone arrangement is observed and therefore wrist architecture just doesn’t matter, more like a certain subset of wrist-bone mutations (some, interestingly, interpreted as atavisms) work OK. And of course there’s no way to tell at this point whether this is a generalizable example or a fascinating anecdote.
So, I acknowledge that “most evolution is neutral” at the molecular-sequence level of analysis; I just don’t give a shit and neither do most people who bother to think about evolution at all.
You acknowledge that selection is important and that phenotypes evidence adaptation, you just think that molecular biology is way more important and foundational than studying phenotypes.
Will you admit that the statement “most phenotypic evolution is neutral’ is unwarranted?
No, seriously, this is really getting to me. Can you describe what you think correlation means? Are you aware of the tight correlation between global temperature and pirates? Have you encountered the phrase “correlation is not causation”? You keep using “correlation” when you mean “causal relationship”.
Chas – I’m arguing for a particular language usage that is fairly common to add clarity, not pretending that organisms aren’t a part of nature. You’re a lumper, I’m a splitter, I don’t think there’s really a fundamental difference there.
Carlie,
I’m not married to the word “correlation”. I like it just fine, because I’m not talking about correlation in just one instance but about some sort of dependable correlation in similar cases, which would strongly suggest a causal relationship. Still, I’m perfectly happy to abandon it in favor of “causal relationship”.
We certainly have more interesting things to argue about. I do think there’s a fundamental, or at least important, difference between your claim that sexual selection is somehow different from natural selection and the claim from Chas and me that mate choice is simply another aspect of the environment experienced by an individual or allele, not different in kind from other aspects such as predators, temperature, or food sources. Any of these might conflict with any other in selective effect.
Sorry for the late reply, I don’t get a chance to sit down and comment much these days.
I get that. You’ll note I (deliberately) didn’t even use the word “evolution” in my post — regardless of the influences involved, it’s all evolution. I was just weighing in on the discussion about the meaning and emphasis of the term “natural selection”.
I suspect I poorly articulated my thoughts regarding artificial selection, so I’ll try and do better below.
I’ll grant your first case is artificial selection in the strictest sense (and would fit my half-arsed vector analogy); but it’s more a case of demonstrating that, given specific environmental pressures, the population will tend to adapt to better survive in that environment. The lab is not so much “breeding a pesticide-resistant fruitfly” as it is showing “if a pesticide isn’t 100% effective, fruitflies will tend to evolve resistance to it”.
But “artificial selection” is, from what I can tell, more typically synonymous with selective breeding, where an external agency is selecting which members of the population get to reproduce. In the above scenario, that would involve the lab worker explicitly isolating the most drug-resistant fruitflies from each generation, and only breeding those for the next. The restriction of the breeding pool due to external agency overwhelmes the natural selective pressures. Here they are “breeding a pesticide-resistant fruitfly”, because that’s the factor they’re using to choose breeding candidates.
But the lab could also be selecting for the biggest wings, and breeding a “big-winged fruitfly”, for example; even though no natural pressures are encouraging this. In the wild, this trait might be a net negative in all cases (too energy intensive, slower, easier target prey etc), but because only big-winged flies are allowed to breed by the lab, the trait becomes fixed in the population anyway.
(I hope I’m getting my terminology right.)
Basically, I thought the whole point of the term “natural selection” was primarily to illustrate that diversity and adaptation can and does occur without directing agency, thus the distinction.
Kagato: you’re right, raven’s wrong. The first case would not be called ‘artificial selection’ by most biologists. That kind of experiment, in which experimental selection pressures are applied but organisms are free to live and breed as they will, is usually called ‘natural selection in the lab’.
Can someone please answer the following stupid, poorly stated question, which comes from my own personal, uninformed head, in the simplest terms possible?
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IF there is a FACT of evolution, which is made evident by demonstrable physical change extending from obvious physical traits down tomthe level of the genome
AND IF it is commonly understood that the MECHANISMS of evolution (with which THEORIES of evolution are concerned) are acknowledged to be changes in the genome due to mutations and effects of the environment (including all the subtle possible interactions these imply)
AND IF any individual form and function depends ultimately on restrictions and possibilities made present in the genome
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THEN how is it that, even though physical change can be appreciated strictly in terms of the changes themselves, any meaningful study of the mechanisms of evolution can be undertaken without specific and thorough reference to the genome itself?
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PLEASE, PLEASE, PLEASE understand that I’m not being silly, or caustic, or ironic here, nor that I think I know a DAMN THING.
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I’m not surprised that I don’t yet get the intricacies of this argument, and I expect very little outside help with that. But I AM surprised that I can’t comprehend even its SHAPE.
mispost
PLEASE IGNORE THE ABOVE POST BY ME
I think this should have been on the “The state of modern evolutionary theory may not be what you think it is” thread.
I’m posting it there.
Can anyone delete this?
There is geographical variation in human nose shape. It just happens not to line up with hair shape or skin color nearly as well as many people believe. People with completely European noses but much darker skin than Obama are common in Rwanda, for example…
It’s really a paper about development biology: the observed variation shows us how the autopodium develops in… salamandrids, and what happens when the development process overshoots, undershoots, or (occasionally) gets diverted. There are straightforward extrapolations for evo-devo.
Only PZ can, and he isn’t going to bother even if he ever reads this thread so far down. :-)
Dale Husband @6, even Darwin included another mechanism, sexual selection, in his theory. But his explanation was far from complete; lacking any notion of genetics, his later editions of The Origin of Species hypothesized inheritance of characteristics acquired by parents in their lifetimes. Evolution was visibly true but the explanation was not solid until the rediscovery of Mendel’s theory, the discovery that DNA carried the chemical template for the amino acids in proteins. Other developments such mathematical analysis of evolution under various circumstance, concepts of molecular evolution, retroviruses and the existence and action of regulatory genes have improved our knowledge far beyond natural selection.
From a practical point of view, you oppose Mike Fair now and opt for science without magic. Then ask for the standards to be reconsidered to include sexual selection and, when you get down to molecular mechanisms, a large role for neutral churn whence adaptive changes spring.
Sorry! “Mendel’s theory and the discovery that DNA carried…”
Markita,
At the risk of restarting an argument, sexual selection is a variety of natural selection.