Is macroevolution impossible to study?
Once again, the Discovery Institute is playing word games with educational systems, trying to give legal protection to religion-based incompetence. I refer, of course, to the ongoing debate about standards in Texas, and the insidious influence that the DI is wielding.
As Wesley Elsberry notes in his summary of the alleged weaknesses of evolutionary theory, an oft-repeated mantra rears its head yet again. This ID tenet holds that macroevolution is either not possible, or cannot be observed, or cannot be studied (or any combination of the these). Apparently, Board of Education member Ken Mercer is of the opinion that macroevolution has not been observed.
This is one of the "weaknesses" that really betrays the many levels of ignorance of the ID proponent. For it implies that, because it would seem to be impossible to replicate a complete macroevolutionary transition that is expected to take millions of years, it is not possible to test specific questions about the process using the time-honored process of hypothesize, test using controlled and repeatable experiment, and revise. This is patently ludicrous.
Worse still, however, this ID claim implies that macroevolution cannot be observed in controlled experimental settings. As the following discusses, this is false. (Of course, I must add a caveat here. When cornered, the ID proponent will define macroevolution as any evolution that has not been observed. Of course, this deflates their objections, or should if one cares a whit about the irrelevance of circular reasoning, but logical consistency isn't something we expect from the Discovery Institute.)
To begin with, it helps to reflect on what might constitute a macroevolutionary transition. Ask yourself, if you might, what distinguishes, say, animals from plants. Curious and perceptive students could come up with an interesting list, and I daresay many of the distinguishing characteristics would trace themselves to a fundamental difference that is seen at the cellular level. Of course, this difference is the presence of an organelle - the chloroplast - in plant cells that is absent from animal cells. This difference distinguishes entire kingdoms, and changes that modified an organism such that it possesses a new, additional, organelle would undeniably be considered as macroevolutionary. Similarly, changes that are clearly in such a pathway would have to be considered macroevolutionary.
Enter into the picture the long-running studies of Kwang W. Jeon. More than 40 years ago, Jeon and Lorch reported the discovery of a novel strain of Amoeba proteus, so-called xD amoeba (2). This strain differed from its parent (the D strain) in that it possessed a bacteria-like endosymbiont (termed XB, and shown later to be related to Legionella species). xD amoeba are totally dependent on their endosymbiont, as removal of the XB bacteria from the xD strain is lethal to the amoeba. xD amoeba possess a number of novel proteins; one of these interferes with lysosomal recognition of the endosymbiont, one (a nuclear protein) inhibits growth of D amoeba, and one (coded for by the so-called s29x gene) is encoded by the XB genome and exported to the cytoplasm. (This is likely far from an exhaustive list of novel proteins found in xD amoeba - I am not aware of proteomic studies that have been conducted with xD amoeba.) More recent studies have shown that the XB endosymbiont directly controls the expression of at least one nuclear gene, possibly via adenine methylation. (This modification is typically found in prokaryotes, and its occurrence in the xD strain suggests that the XB Dam methylation system can access the nucleus of the xD strain, perhaps by the same mechanisms that allow the s29x protein to pass from endosymbiont to cytoplasm.)
Reflect, now, on the ramifications of this system. Organelles such as the chloroplast and mitochondria arose by endosymbiotic events. What we see with xD amoeba are the early stages of another such event. The xD strain is dependent on the endosymbiont, much as plant cells depend on chloroplasts, and eukaryotic cells on mitochondria. Moreover, as is the case with more recognizable organelles, gene expression and cellular physiology in the xD strain have become interdependent, such that endosymbiont and nucleus communicate and control expression and metabolism. This system is arguably the beginnings of the evolution of a new organelle, something that would be tantamount to the origination of a new kingdom.* By any reasonable measure, what Jeon and his coworkers have been studying is an example of macroevolution. His system stands out as a refutation (NOT the only one, but merely one interesting example of what are likely many) of this oft-repeated (and erroneous) ID claim, that macroevolution has not been, and cannot be, observed or studied.
A recent review that can be used to follow the history of this fascinating system:
1. Jeon, K. W. 2004. Genetic and physiological interactions in the amoeba-bacteria symbiosis. J Eukaryot Microbiol 51:502-8.
A few other selected references:
2. Jeon, K. W., and I. J. Lorch. 1967. Unusual intra-cellular bacterial infection in large, free-living amoebae. Exp Cell Res 48:236-40.
3. Jeon, T. J. 2008. DNA adenine methylation of sams1 gene in symbiont-bearing Amoeba proteus. J Microbiol 46:564-70.
4. Jeon, T. J., and K. W. Jeon. 2004. Gene switching in Amoeba proteus caused by endosymbiotic bacteria. J Cell Sci 117:535-43.
5. Lorch, I. J., and K. W. Jeon. 1981. Rapid induction of cellular strain specificity by newly acquired cytoplasmic components in amoebas. Science 211:949-51.
6. Pak, J. W., and K. W. Jeon. 1997. A symbiont-produced protein and bacterial symbiosis in Amoeba proteus. J Eukaryot Microbiol 44:614-9.
* - what seems to be missing from the xD amoeba are examples of bacteria genes that have picked up and moved into the nucleus. Such examples may remain to be discovered, or it may be too early in the evolution of the system to expect such events. Regardless, if and when the pertinent experiments are done, they can be expected to shed interesting insight into the movement of DNA between compartments in other systems.
Postscript - I would appreciate any pointers to studies of this system that have been authored by other groups, or papers that do not appear in Pubmed or Google Scholar. These may be left in the comments, either on The Panda's Thumb or here.
49 Comments
djlactin · 21 November 2008
But you're dind't saw it happen! Godmustadidit! HAH! pwned!
(poe)
DS · 21 November 2008
The evidence for the endosymbiotic origin of both mitochondria and chloroplasts is so convincing that only someone who was totally ignorant of the evidence would ever claim that macroevolution is impossible, or cannot be studied, or can not be observed, or any combination of these.
Once again, a well informed public is the best defense against such ingorant nonsense. Hopefuly enough people still value education and science that, in the words of Lisa Simpson, we won't let the butt heads win.
tresmal · 21 November 2008
Does anyone know why the endosymbiont is necessary to the amoeba?
ravilyn sanders · 22 November 2008
The endosymbionts will be seen as macro evolution by scientists and the learned. But the creotards are not interested in understanding any term nor are they stumped by ny logical inconsistency. Because what it is described involves "microbes", the demagogues will simply say "Ye, faithful! Lo! What these dumb materialistic Darwinists are saying. Some evolution happening in microscopic bugs and is touted as an example of macroevolution! Darwinism is clutching at straws. Rejoice! It is in its last legs. Please donate generously to help me fight and defeat these evilutionists and bring the Kingdom of God on Earth! Hallelujah!"
I would suggest we talk more about the "Ring species". It is essentially macro evolution happening and going on right now, and we are witnessing it. The salamanders in that California lake, two species of gulls around the north pole, the green warbler species around the Himalayas excellent examples.
It is impossible to convince the creotards. But the genuinely moderate people who are not knowledgeable enough to be aware of endosymbionts and eukaryotic enslavement of the downtrodden underclass of mitochondrians etc are more likely to understand and appreciate the "Ring species" better.
Of course non-biologists like me who love the logical explanations provided by the biologists explaining the diversity of life, typical readers of Dawkins, Dennet, Ghould and Shubin books, will take the trouble to understand the argument and express admiration for the work. But to get past the propaganda of the Deception Institute, a series of six stuffed dolls of Herring Gull transitioning to lesser black backed gull marketed to children is a better idea.
John Vanko · 22 November 2008
Macroevolution HAS been observed, and can be observed today by anyone with an unbiased, open mind. The entire Fossil Record IS the Fact of Evolution, that crys out for an explanation. The best explanation is the Theory of Evolution by descent with modification through natural selection.
We DO observe evolution in progress, for millions of years into the past (thanks to Physics we know the time span). We have a time machine, and it is called Stratigraphy. It does not depend upon radionuclide dating techniques. It depends only upon Steno's observation (law) that younger beds are deposited upon older beds. (Some, if not many, creationists deny this - they have to or their entire belief system falls apart.)
Happily, we have the entire science of Physics to give us temporal bounds on the layers in our world's Stratigraphy. (All of the sciences of Stratigraphy, Paleontology, and all of Physics, have to be wrong for Creationism to be correct.)
Each and every fossil, in every museum cabinet and in-place in all the sedimentary rocks of the whole world, constitute the FACT of Evolution which the THEORY of Evolution seeks to explain.
Opisthokont · 22 November 2008
It is correct to say that there are countless more examples of obligate endosymbioses. Perhaps the most remarkable is Paulinella chromatophora, another amoeba which appears to be on its way to acquiring a chloroplast. It is always found with two cyanobacteria inside its cells, and cannot live without them; furthermore, its closest relative eats only cyanobacteria. On the mitochondrial side, there is a whole "spectrum of mitochondriality" from the highly bacterial-like Reclinomonas through plant and animal mitochondria, various types of anaerobic mitochondria, hydrogenosomes, mitosomes, and finally tiny double-membrane-bound organelles that may or may not be the relics of the mitochondrial endosymbiont but are so reduced as to be hard to prove as such. Each of these carry out their own biochemical processes, and each shares relatively little genetically with all the others, but there is always some clue to their relatedness that renders any other hypothesis extraordinarily improbable.
I must take issue with the assertion that the evolution of a new endosymbiotically based organelle "would be tantamount to the origination of a new kingdom". Kingdoms are a taxonomic construct, and so should be defined phylogenetically. To place a single strain of a single species in its own kingdom implies that all of its sister strains are similarly worthy of kingdom status, something that I doubt would be a worthwhile construct. Eukaryotic cells, meanwhile, vary tremendously within kingdoms, and the acquisition of a novel endosymbiont in a single strain of a single species is not so remarkable as to warrant that level of distinction, any more than the acquisition of language makes humans no longer animals.
John Kwok · 22 November 2008
Stanton · 22 November 2008
Stanton · 22 November 2008
mafarmerga · 22 November 2008
Greg · 22 November 2008
Neat stuff.
Species name should probably be "Amoeba proteus," not "Ameoba proteus," I think....
Torbjörn Larsson, OM · 22 November 2008
Arthur Hunt · 22 November 2008
Hi Greg,
I fixed the typo. Thanks for catching it.
Art
Henry J · 22 November 2008
Daniel Gaston · 24 November 2008
Matt G · 25 November 2008
Something else crying out for an explanation is the appearance of different clades of mammals on the different continents. There is a wonderful (and downloadable) pdf file at the BBC which clearly shows these relationships:
http://news.bbc.co.uk/2/hi/science/nature/6503045.stm
If this link doesn't work, try:
http://tinyurl.com/67tn4m
An especially nice touch is the "you are here" label.
bill · 25 November 2008
I would suppose that a creationist could never convict someone of a crime based soley on the evidence collected, no matter how compeling, if no one had actually "observed" the crime being commited.
John Kwok · 26 November 2008
phantomreader42 · 1 December 2008
Is "macroevolution" impossible to study? Yes, because the word "macroevolution" is a word with no meaning at all! "Macroevolution" means nothing but whatever strawman the current creationist needs to throw out to hide from the evidence. They just claim that "macroevolution" has never been observed (usually without even pretending to define the term in a meaningful way), and pretend this is some kind of deathblow to science. They can't offer a speck of evidence that establishes any barrier between "microevolution" and "macroevolution", they don't bother to clearly define where they claim this barrier is, and they'll move the goalposts on an instant's notice. Any observed instance of "macroevolution" and they change the meaning of the word. "Macroevolution," as used by creationists, is nothing more than a pointer to an ever-shifting pile of strawmen that exist only in their hollow heads. It is a term without anything resembling meaning.
John Kwok · 1 December 2008
phantomreader42 · 1 December 2008
John Kwok · 1 December 2008
Dear phantomreader42,
I don't disagree with your assessment of the term "macroevolution" as used by creationists:
"When used by creationists, 'macroevolution' is, and always has been, an utterly meaningless, ever-shifting, deliberately underfinable term. Any scientific meaning has no relevance to these nutcases. Give the word a definition, and it can be observed, and has been, but that fact just sends the creationists into ever-deeper denial."
However whenever you do refer to it as "meaningless", PLEASE EMPHASIZE too that it is a scientifically meaningful term when used by paleobiologists and other evolutionary biologists interested in studying these phenomena as seen from the history of life on Planet Earth.
John
fly · 2 December 2008
Heck with macroevolution, microevolution has never even been validated. Never once has science pinned down a random genetic change that has been proliferated by natural selection. I'm here if anyone would like to present evidence to the contrary.
fly · 2 December 2008
I would like someone to present evidence for Micro-evolution....this must include a random mutation that gets proliferated by natural selection. Thank you.
Dan · 2 December 2008
fnxtr · 2 December 2008
go away bobby.
fly · 2 December 2008
I've Got "What evolution is" by Mayr....nothing there.
Anyone care to present even one case of microevolution? I need to see the random mutation and I need to see natural selection -- and I would preferably like to see them add a new morphological trait. Can someone just do this for me without giving me the runaround?
Stanton · 2 December 2008
Science Avenger · 2 December 2008
Dave Luckett · 2 December 2008
You mean you want to see things changing shape right before your very eyes, just like it happens in the cartoonies?
DS · 2 December 2008
fly wrote:
"I need to see the random mutation and I need to see natural selection..."
Yea and I need to see the earth go around the sun.
On the off chance that you are serious, here is an oldy but a goody about the evolution of antibiotic resistance in bacteria:
Genetics 160:823-832 (2002)
If you are bobby this reference has been provided to you before. If you are not then perhaps you will read the paper and then admit that it gives a perfect example of exactly what you asked for.
fly · 3 December 2008
yea, nylonase is actually 140 mutations. How do those arise randomly?
John Landon · 15 December 2008
The question of macroevolution requires a new approach, for the evolution of man, as visible in the study of the eonic effect.
Consider commentary on this post at:
http://darwiniana.com/2008/12/15/macroevolution-impossible-to-study/
kathy doolin · 28 December 2008
Will I EVER find a discussion group that does not denigrate others views by attacking the person? I was so enjoying this discussion, and then you had to start calling people IDiots. Please folks, keep it civil. Remember-once you label me, you negate me.
kathy
Joe G · 18 February 2009
Once again Art erects a strawman and beats it down!
You go Art. I bet you are still proud of yourself!
What I mean is the way you have defined macro-evolution not even YECs reject the premise.
You guys seem to do that quite a bit. Take something that your opponent says then redefine it to suit your needs.
But anyway keep it up. Soon you will have torn down all the strawmen you erect.
And the good part is you don't even know you are doing it.
IOW we are not laughing with you, we are laughing at you and your feeble attempts to support your faith.
fnxtr · 18 February 2009
saywhatyouwill · 28 February 2009
Joe G is correct in this instance. 'Speciation' is far from denied by non-evos, even YECs use it as part of their explanations for the diversity of life! So it's a complete strawman to argue that speciation (or 'macroevolution' or whatever you wish to term it) somehow defeats (or even bothers!) informed non-evos. Moreover, arguing that something is 'on its way' [I'm paraphrasing the last paragraph in the article] to being a proof of anything is meaningless in the case of evolution, considering evolution is a directionless phenomenon with no goals. That's not to say this won't be the first step, but for now it is all that it is.
Stanton · 28 February 2009
saywhatyouwill · 1 March 2009
Dan · 1 March 2009
saywhatyouwill · 1 March 2009
Flint · 1 March 2009
Dan · 1 March 2009
Henry J · 1 March 2009
Dave Luckett · 1 March 2009
I call on whatever gods there be to witness: here's a bunch of scientists ferociously arguing with each other over the exact nuance of an interpretation of a description of a process they all agree on; but over there at DI and AiG, the lugenmeisters are in perfect accord in public and all is sweetness and light, even though they are at total odds with each other over virtually everything. Truly, humans are wonderful animals.
Mike Elzinga · 1 March 2009
saywhatyouwill · 1 March 2009
Dan · 2 March 2009
saywhatyouwill · 2 March 2009