Having engaged in a debate with a relatively well informed Creationist recently, I wish that the Mailbag Answer had not brought up the Peppered Moth/Predation example. While this is a nice simple example used to demonstrate changes in allele frequency over generations in adaptation to environmental changes, bird predation is not necessarily the determining factor that it was put forth by Kettlewell. The moths do not naturally rest on tree trunks in the daytime as assumed and depicted in photos. Kettlewell released the nocturnal moths during the day (the better to see them) but this is not their natural behavior and therefore results and inferences drawn there from don’t necessarily apply.
What it boils down to is that (sometimes flawed) assumptions are made, explanations that appear to be the best suited to the (sometimes flawed) data gathered. It could be that the changes caused by the industrial pollution could have affected the mating or gestation of the white moths, we really don’t know and further research appears to be in order.
A debate and a article were of valuable insight into the issues.
While I (mostly) accept the theory of evolution, and certainly find it a lot more compelling than anything I’ve heard that could be labelled creationist, I found the bald statement that there is no difference between micro and macro evolution distressing. There is a big difference, and that is that people have observed micro evolution and they haven’t observed macro evolution. It’s possible to make a good argument that they are the same, but it’s bad science to fail to maintain the distinction between what you know and what your theory predicts. And it is often the case that the first extrapolation of some micro observation into macro phenomena is done wrong – that’s why people test theories.
I know that most people think that this distinction is silly, but I believe that failing to make it undermines the credibility of good scientists, and also results in a lot of bad ones. We are constantly bombarded by, for example, “scientific studies” of the value of some dietary change or other, and then a few years after every bakery in town starts selling bran muffins, we hear that it doesn’t help at all. Maybe these studies are all flawed because there is a bug in SPSS, but in my too many years in academia I listened to unnumbered people in the “soft” sciences make logical errors like the one in this column, and they’d then misapply statistical methods and come up with “astonishing” and probably bogus results.
It’s not a “bald statement,” it’s a discussion of facts. Did you read the entire answer?
Yes, actually, they have. They’ve observed it in the fossil record and they’ve observed it in nature. There is no magic dividing line saying, “evolution stops here” between species. I thought the Mailbag answer made that pretty clear…
Cheap: Interesting. I didn’t know that. I’m going to look into it more. Anyway, whether that particular example is flawed or not, that’s what creationists think of a “microevolution.”
Lib: Definitely don’t mention it. Whatever “it” is.
Sigh… Unbelievable to me that this is still being debated, as though science hasn’t moved since the 1920s. Or was the Scopes trial in the 30s?
Anyway, we HAVE observed macro-evolution in terms of the extinction of species, such as the dodo and the passenger pigeon… and, I wish, the Biblical-literalist, but that will take a few more generations, I’m afraid.
I apparently failed to make it clear that I am not supporting “creation science”, which I regard as at best a failed attempt at humor.
I did read the entire article, and it seems to me that there is a difference between direct observation and looking at the fossil record. I’m objecting to failing to be precise about what is known and what is deduced – the latter is even more likely to be wrong than the former. I used the word “bald” advisedly, since I felt that the rest of the article merely restated the position rather than expanded on it a meaningful way.
This reminds me a little of historical debates about general relativity. Some people regarded it as being settled since there was experimental support for special relativity, and the perspective was so ingrained that apparently many people couldn’t see how it could be otherwise than true. I used to be an applied mathematician and I often saw this same kind of confusion – the model looked okay at some micro level, so it must be okay, and therefore we can turn the crank as hard as we want on it and believe the results. Usually it didn’t work out. The history of science is littered with discarded theories that were completely obvious. I doubt that this is one of those cases (I’d be very surprised if it is), but it isn’t that much harder to keep the limitations of what is known in mind.
Since I am not by any means an expert on biology of any kind , I am prepared to accept that I’m missing something here, but I was an expert at smelling out the kind of mistake I’m complaining about.
About that comment on relativity… Special and general relativity are really two completely different theories: Yes, GR is completely consistent with SR, but it’s a lot more than just an extrapolation of SR. SR has probably been proven more thoroughly than any other scientific theory in history, but nobody (at least no physicists) claim that that means that GR is proven. There are, in fact, proofs of GR, but they’re essentially unrelated to the proofs of SR.
For the record I wish to state that I’m not a creationist (as mentioned I was engaged in a debate with a Creationist/Intelligent Design Theorist). I’m all for the Scientific Method, but beware Ockham’s Razor, it can cut you when you assume the ‘obvious’ and ‘simplest’ solution. Often things are more complex than they first appear to be.
I don’t want to quibble, but the statement that all of evolution, micro- and macro-, relies on a single mechanism is contrary to Darwin, at least. He proposed two mechanisms, sometimes acting in concert, sometimes independently. The first, of course, was the sort of natural selection usually called “survival of the fittest”; the second was sexual selection, which could perhaps be called “survival of the cutest”.
I actually hate to use the term “creationism”, which implies that it has some scientific legitimacy as a theory. I prefer to stick to Biblical-literalists and other such terms, to make it clear that they have no claim whatsoever to being a “scientific theory.”
PStamler: I don’t think anybody said evolution relies on a “single” mechanism (correct me if I said otherwise). I said macro- and micro- are the same.
Hardlyb: I already noted that it has been observed in nature. Here are some links for you on observed instances of speciation (sorry I didn’t post them sooner – they are posted so frequently around here I just figured everybody had seen 'em by now).
http://www.talkorigins.org/faqs/speciation.html Dex: I don’t see how “creationism” implies anything about the scientific legitimacy. “Scientific creationism,” which is their preferred nom de plume, does pretend to science but is actually an oxymoron, so you won’t see me using it except when describing what they call themselves.
What I don’t get here is how we can mention puncutated equilibrium and still say that macro-evolution is completely viable.
As I understand it, punk eeq says that there are points in the fossil record where it seems impossible for classic Darwinian macro-evolution to have occurred in the time shown. The “Cambrian explosion” is the example I have seen cited. So how can Eldredge and Gould be used as supporters of what I would think is meant by “macro-evolution?” Or has the term changed to mean the change from one species to another, no matter what the time period or driving cause?
I have been lead to understand by more than one book that believing in the slow, grinding type of macro-ev is a little like believing in the ether of space for light to travel in. Is this not the case?
Calling the extinction of the passenger pigeon “macro-evolution” is patently bizarre. Of course, a species can be wiped out by simply eliminating its ability to be successfully procreated (e.g., kill all the females, and --boom). That says nothing about the ability of a species spontaneously to appear.
There is an essential difference between these two things:
A) shifts in population distribution (like the moth example, or extinction due to overharvesting, as the passenger pigeon, dodo, etc.): These do not require the generation of new genotypes, but change their relative numbers.
B) initial appearance of a new species with its own karyotype: It is, unfortunately, seldom noted that different species, even if morphologically “related” will have different numbers of chromosomes. This may not sound like much, until you understand what a chromosome is. “Micro-evolution” may include “speciation” on a small level, but the kind of mutation necessary to change an organism’s karyotype is sufficiently different–and sufficiently risky–to be considered a distinct genetic phenomenon.
But when people don’t know the difference between a gene and a chromosome, this distinction sounds meaningless.
OK, let me put it this way: The number and length of chromosomes (karyotype) is an essential definer of your species. The genes are parts of the chromosomes, and work as such. Don’t believe me? If you broke up the chromosomes, but kept all the genes, in a cell, it’s questionable whether it could divide, and it would very likely die. Missing a chromosome pair can doom an embryo from the outset. If we look at speciation as a genetic phenomenon, we have to have a model for the appearance of organisms with extra chromosomes, or with chromosomes fused together, lessening the chromosome count. This is a big deal, and calling it the same process as the other is mendacious.
To Chronos: I’m aware that SR and GR are different, and that GR isn’t considered completely validated. When I was at Stanford there were some people on the faculty that were designing experiments to test aspects of GR, and I noticed recently that one of these experiments had been conducted and the results were described as agreeing with theory. I also remember listening to some physics graduate students arguing about whether or not it was worthwhile to test GR – some of them seemed surprised that there was anything to check, because they had internalized the theory so completely that it seemed beyond question. That was the perallel that I was commenting on.
Perhaps my objection was too fuss-budgety, but I’ve seen cases of this sort of blindness to this distinction lead to hubris. Anyway, at least some people on the thread appear to get my point, and I’m getting bored, so I’ll let it go at this.
I agre with some of what you say (especially about the passenger pigeon), but one thing you said caught my eye:
That’s a new one on me; there’s a discussion of several definitions of “species” at Observed Instances of Speciation (which is the same as the first link David posted above). Perhaps that’s a little out of date, but it mentions nothing about karyotype. Can you expand on your statement a bit?
Do you think that the examples given at that link, and the other link posted by David, are indeed speciation?
Um, because punctuated equilibrium is an explanation for evolution, including “macroevolution.”
Sort of.
Punctuated eqilibrium says that “equilibrium” is the norm – there are changes, but not a whole lot. Unless, that is, something happens to change the environment. Then, changes happen much more quickly than usual as organisms find new niches to fill.
Because you appear to misunderstand.
Don’t forget, it was Eldredge that I quoted in the Mailbag item, so I would think he’d know!
But the point is that mutations and natural selection can cause species to split off into new species, etc. Punctuated equilibrium certainly doesn’t say anything against this – in fact, it is an explanation as to how it happens.
I don’t think so. There is still debate in this arena, and in some ways it depends on terminology. One argument Dawkins has with Gould, for example, is that Dawkins says Gould’s “discovery” is nothing new – it’s just a change in terminology. But it comes down to this – sometimes evolution is slow and plodding. Sometimes (such as when there is significant change), it’s faster. It depends a great deal on the environment.
The mailbag did define macroevolution, but I don’t think that either of those examples fit the definition.
The earliest experimental support for general relativity was the famous eclipse observations in 1919–which propelled Einstein to international celebrity status. How much those experiments actually supported GR, well, that’s another story.
Are you sure? I thought sexual selection was included in natural selection–at least it is in my biology book. Did Darwin separate it out?
My point about the dodo and the passenger pigeon was not to prove that species are mutated into other species, but that species change – either micro-changes, like the moths, or macro-changes, like extinction. That is, step one towards accepting evolution is to accept that the species of 4,000 years ago are NOT identical to the species today. Sorry if I was unclear. Extinction (failure to procreate) is an important part of evolution.
