This is odd. There is no real, academic debate on “gradualism vs. punctuated equilibrium” anymore, as if either one of them are 100% the case. Rather, they are two ends of a spectrum, and in order to debate them, you have to draw an altogether imaginary line on the spectrum and say, “OK, on THIS side, we have gradualism, and on THIS side, we have punctuated equilibrium.” It’s silly. Any speciation event has to be considered in its specific context of gene flow, drift, selection, biogeographical context, and time scale.
In most cases, the fossil record isn’t complete enough to distinguish between gradual and abrupt change. OK, you find one fossil, and then you find another fossil of a critter that you think descended from the first one, and it’s significantly different. Does that mean that large changes appeared quickly? Maybe not, if there’s a span of a million years between them.
Eh, Gould used those same whales to support punctuated equilibrium. Look, an actual link!
I’m surprised to see so much (anecdotal) posting about gradualism; I really find punctuated equilibrium seems to match better with observation, and didn’t realize modern theorists put a lot of stock in gradualism.
I think modern creationists put more emphasis on gradualism than Darwin ever did (because they’re setting up a straw man to refute). Say, speaking of that, what’s your overall position on evolution itself?
The fossil record is not a great source of information on the actual, down-to-brass-tacks, process of evolution. It’s a book with lots and lots of pages missing. If we want to get down to cases, let’s talk about cases.
The Intelligent Design Community seems to have adopted Dr Margulis as a victim of the neo-Darwinists. A commenter did note that…
However, another clever ID’er revealed The Plot Against Her:
To understand Darwin’s basis for phyletic gradualism you have to know the context in which he formed it, specifically a view of the world in which the environment changed slowly, if at all. Radical changes in the physical environment or other selective pressures were regarded as uncommon and improbable because the world itself was considered to be unchanging. The specific units of inheritance were not widely known (Darwin, as well as the wider world, was unaware of Mendel’s work on genetics) which made it difficult to understand or model the effects that changes in selective pressures would have statistically on a population. This philosophy of development became entrenched in Darwinist selection, and because the alternative appeared to be something like Lamarckian acquired characteristics–in which novel characteristics or behaviors could be introduced into an existing population–it remained largely unquestioned, even after genetics became widely known.
However, the revelations by George Williams and John Maynard Smith on the game theory applications to evolutionary mechanics that while populations tend to return to an equilibrium after moderate changes in selective pressures–and hence, why organisms form into cladistically-discrete populations (species) that are identifiable over geologic periods and eras (and in some cases even eons)–but that dramatic changes in the selective environment can result in radical changes in a swath of species, which is in essence punctuated equilibria on a modern synthesis basis. Hence, there is no disconnect between punctuated equilibria and so-called “neo-Darwinist” theory. Gradualism occurs as long as dramatic changes in selective pressures do not exceed a threshold, and this threshold may be environmental change (in the selective sense) that stems from a change in the physical environment, arrival of a new species, extinction of an existing keystone or foundation species, the exposure of new resources, geographic or sexual boundaries (allopatric and sympatric speciation), et cetera. The need for “hopeful monsters”–radical but viable mutations or hybrids that provide novel successful advantages or phenotypes–disappears, as it is not required to explain what appear to be sudden changes in the characteristics of a population or breaks in speciation; only the pressures that have previously reinforced the existing equilibria have changed.
As for adaptive co-evolution or sympathetic evolution, not only is it not foreign to modern evolutionary synthesis but it actually flies in hand with some of the more radical notions developed from it, and specifically the concept that the influence of the gene extends beyond the gene carrier, and pressures upon it are similarly influenced by more than simple reproductive success as the organism level. While the “extended phenotype” model is understandably difficult to simulate in any complex system, the basic concept–that the gene not only acts upon the organism, but upon the success of other species that may depend upon the organism in some way, and even upon the overall selective environment–is conceptually clear. A gene that makes a hyena faster also influences the wildebeest, and its ultimate success in the gene pool relies upon being not so fast that it radically changes the establish equilibrium between prey and predator.
The course of evolution in the selective environment is less like a race with the Red Queen than a ballroom in which the steps are all modest variations repeated over and over until the music changes, and those who can’t go from foxtrot to tango get left on the sidelines. Cooperation in evolution is like cooperation in economics and business; it is critical to long-term success, because you can’t be vying with every potential rival all the time, and sometimes it is in both parties best interest to merge into a single organism. But even within cooperation there are selective pressures that have every individual organism competing with every other, whether within a species or across genera.
As for punctuated equilibria itself, as others have pointed out this may be in no small part an artifact of the incompleteness of the fossil record and the difficulty establishing good baselines for evolutionary change. However, at least for many recent species, we have a pretty decent record that indicates that while gradual development occurs in static environments, a significant change in selective pressures can result in some very radical changes in a species population, and the revelation of previously latent phenotypes that may have provided no specific advantage prior but now bestow substantial reproductive advantage.
Stranger
Stranger
Gosh, y’all, sorry! It’s just that some of you writers are so funny I couldn’t resist a little “czarcasm” of my own!
And hey, Ogre, she does too talk about the finches! You might want to read the article.
And I know I’m prolly not as edgycated as y’all, but as far as I can tell Lynn’s all about stuff eatin’ stuff and stuff copulatin’ with stuff and then you git new stuff after eatin’ and copulatin’. Wouldn’t you like to get a peek inside her laboratory?:eek:
Really?
The Discover article would suggest that’s the case (though I don’t know much about her otherwise). What got me in that article (beyond her uncritical use of a couple of the old creationist canards) was her overconfidence in the explanatory power of her own theory. At one point she’s talking about cilia in retinal cells (or something similar), where the clear implication is supposed to be that at some point ciliated bacteria moved in wholesale and set up camp in the eye so they could get nutrients while the larger organism got the benefits of the cilia. She was talking about how these cilia are JUST LIKE the ones you see in some bacteria.
Well … so? She seems to assume that the only alternative to her hypothesis is cilia being re-evolved de novo in multi-cellular organisms (which she argues is impossible), but that’s not the case. Practically every other bacterium and single-cell critter in the microscope has cilia attached. All it would take is for the common ancestor of multi-cellular animals to also have them, and for the gene(s) involved to find enough utility thereafter to be preserved. (As an aside, even genes of little to no use can be preserved for a surprisingly long time: birds haven’t had teeth for 100 million years or so, but their genes can still produce bits and pieces of teeth when introduced into a more friendly environment.) Which is more parsimonious? For the ancestral bacterial gene(s) to be preserved, with modification, throughout the subsequent evolution of multicellular animals, or for umpteen new bacterial endosymbionts to set up camp as needed: one for ciliated eye cells, one for ciliated gut cells, etc?
The bit about the finch beak studies also bugged me. Not even so much due to the conclusion she drew, but how she approached it. She dismissed (by implication from what she did say) any consideration of speciation as something that can happen through time If you follow a population for a hundred years and they undergo changes in that time, who’s to say that what you wind up with in the end is NOT a separate species from what you started out with? You can’t go back and put them side by side anymore to see if they’ll reproduce; the original population is gone. Maybe nowadays you could study genes to try to tell, but even ten years ago you couldn’t. She may be right in her assertions about the study (maybe there were no new species, nothing even remotely close and not headed that way either – don’t know anything about it so can’t say), but arguments are wrongheaded regardless.
You could fill a book series on the topic of “brilliant scientists who fall too deeply in love with their own insights”, but it doesn’t make them any less annoying.
Fundamentally, yes. While she’ll acknowledge that competition–both for resources and reproductive success–does occur, she then turns around and relegates it to a restrictive aspect of evolutionary development, and then jumps upon her hobby horse and runs steeplechase with endosymbiotic theory, including and specifically the emphasis of lateral gene transfer. This in and of itself is not the problem; her hypothesis provide interesting fodder for discussion that are ultimately falsifiable in specific cases, and by extension, the fundamental principles. Lateral genetic transfer is a real and demonstrable phenomena, but not one that occurs en masse to an entire population that would support any saltation-type theories. Endosymbiosis is widely–I daresay almost universally–accepted, but as a special case of competitive advantage, not a driving principle that cooperation is a goal in and of itself.
Stranger
Hey, I found another quotation from Doctor Margulis:
Scientists often disagree vehemently about details. But they agree that Creationism is dead wrong. Is that simplistic enough for you?
Sorry to contradict you so directly, friend, but these gentlemen were each claiming the mathmatical impossibility of each other’s proposals. So what is it about math facts that you don’t understand?
The Margulis interview has a hilarious bit about some evolutionist’s math that doesn’t add up too. She reveals that it doesn’t matter if the math doesn’t work out in the end. What matters is if the grant money adds up!
Do you have anything else to offer us? (Oh, and don’t condescend about “math facts” after your Just Folks ignorant act.)
You’re long on assertions and short on cites. Being new around here, you might not know this, but that isn’t going to get you anything but ridicule if you continue. If that’s what you’re here for, then fine. If not, you might want to sharpen your debating skills a bit.
Bridget, Bridget, Bridget,
First I noticed you assumed I’m a man and now a “creationist” too? Please tell me you’re not a scientist! A psychic, an artist, a bookie… Anything but science!
Yeah, that’s daft. See also: allopolyploidy, a speciation process which has been observed happening, has nothing to do with symbiosis of any sort, and results in unequivocally different species (let’s just go with the biological species concept here, folks. They can’t mate with the parent lineages.)
Well, gee, John I’ve cited quite a few ideas which seem to be worthy of ridicule to me. I thought that was the idea here. :smack: Oh well, thanks for showin’ us greenhorns the ropes!
Rattling off ideas does not constitute a cite. When and were did you happen upon this alleged debate about the origins of bird flight, and who were the participants?
Sorry to be so uncitely y’all, but how ‘bout holding all those other rattlers to the same standard? Shake out all the rattlin’ and whatdaya got?
How about this: All y’all read the Discover interview that a fair number of you haven’t read yet but still like to comment on and then we’ll talk and have a real good time!
Now with Sciencey Bits!!!