How could these parasites' life cycles evolve?
Click on picture to enlarge
This and the following illustrations are from the website of Prof. Matthew Bolek of the Dept. of Zoology at Oklahoma State Univ.
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How could the complex life cycle of the above parasite evolve by means of a random process when it is impossible to even imagine a process for such evolution?
Other extremely complex parasitic relationships and life cycles of parasites are described in another post. Parasitologists should be among the leading Darwin doubters, but we have not heard much if any Darwin-doubting from them.
The following text accompanies the above picture:
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Trematodes have some of the most complex life cycles in the animal world and usually include three hosts. Our current studies concentrate on trying to understand the evolutionary avenues for and constraints on the transmission of these parasites to their amphibian hosts. Currently we are investigating two aspects of amphibian trematode life cycle evolution: 1) we are comparing the differences in life cycle strategies among closely related congeners and mapping those similarities and differences on current phylogenetic hypotheses, and 2) we are examining the role of anuran tadpoles in the truncation of trematode life cycles from three to two hosts.
We work on the avenues for and constraints on transmission of frog lung flukes (Haematoloechus spp.) and the role of second intermediate hosts in these life cycles. Most frog lung fluke life cycles have been shown to use odonates as second intermedite (sic) hosts. However our studies in Nebraska indicate that there is a lot of variation in the use of second intermediate hosts among congeners of frog lung flukes. See frog lung flukes.(shown and discussed below)
Click on picture to enlarge
Four representative frog lung flukes. Haematoloechus coloradensis and H. complexus are second intermediate host specialists where the cercaria can attach to any body region of aquatic arthropods. Haematoloechus parviplexus is a second intermediate host specialist and can only infect dragonfly by passively entering the rectal breathing apparatus, whereas H. longiplexus is intermediate in its host specificity and can infect dragonflies as well as damselflie.(sic)
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posted by Larry Fafarman | 8/26/2008 01:29:00 AM
18 Comments:
Larry wrote, "How could the complex life cycle of the above parasite evolve by means of a random process when it is impossible to even imagine a process for such evolution?"
This is a classic Argument from Ignorance, a logical fallacy. Larry fails, again.
@ Nada,
I've begun to think of this blog as a way of sharpening my fallacy spotting and naming skills. Learning can be FUN!
(I find the word verification "phffh" ticklish. :-})
Parasitism is highly motivated, since the payoff is huge.
Larry, since you claim that "Just-so stories are not accepted here," please explain why the Designer takes an interest in promoting parasitism?
Can Anonymice who don't know what ID proposes and don't care to know, explain why they are so interested in speculative questions about "why," which are beyond the domain that ID investigates? ID proposes to show that intelligence played a role in designing some features of life, but not all of them.
Some of the properties of parasites might thus be the product of mechanistic factors, not of design. ID doesn't deny that new forms have descended from old, or claim that mechanistic factors played no role in the origin of this or that critter.
And ID itself can't say whether there was one intelligence involved or a great many such intelligences. It's conceivable to me that each living thing has had something within itself that can design or redesign genes, so that there might even have been as many "designers" as there have been living things on earth. That's about 10 to the 40th power of them, by one estimate. Possibly all looking out for their "own interests."
When I've been in a speculative mood, I've occasionally wondered whether if ID is correct (and I'm not sure that it is correct), there could even be a denumerable infinity of so-called designers; although I don't feel inclined to speculate about a non-denumerable infinity of them.
Christians and other theists have played the main role in the development of ID, but they aren't the only ones involved. With my Buddhist-influenced way of thinking, I'm inclined to avoid speculative questions about the nature, number or qualities of "designers," if any "designers" exist.
Theists who for religious reasons are convinced that the intelligence(s) involved must be God, no doubt have their own theological views about the parasites.
In my case I find it hard to believe that a Creator-God would design a flagellum, say; or that space aliens would design one, either.
But what I find hard to believe, might still be correct. ID deals with all so-called "designers" which can be conceived, in our thought: not with any one particular "designer," that is alleged. Don't Darwin-buffs ever think abstractly?
I've never seen any sign of a plot hatched by Christtians or theists, to create a "theocracy," or teach Adam-and-Eve in schools, or to perpetuate some other religiously-inspired mischief. And if there were any sign of it, I'd be as opposed to it as anyone, I can assure you.
>>>How could the complex life cycle of the above parasite evolve by means of a random process when it is impossible to even imagine a process for such evolution?<<<
Such a lovely example of how creationism/ID/"challenges to evolution" fails to promote critical thinking. Rather than sit down, analyze the problem, and try to see if evolution can offer a solution, Larry says "Look how complex it is! Evolution can't explain that!"
But it can.
First let's look closer at the problem. The isue is how such a complex life cycle can arise for a parasite. So let's set some parameters.
First, we'll start out by making the problem manageable in scope. We are not asking how an organism can evolve to be a parasite, but instead how a parasite evolved a complex life-cycle. Let's also allow for "grainyness" in our changes - each step may represent a number of small mutations. For our argument, let's assume that the parasite starts out with a simple life-cycle rquiring only one host. Can we build a rough sketch showing evolution can provide a way to get to the current complex life-cycle?
First, the life-cycle. The adult parasite lays eggs, which the host frog excretes. Snails ingest the eggs, which then hatch and incubate inside the snail. They eventually leave the snail and go free-swimming. They then attach to a dragonfly nymph. They continue to develop as the dragonfly metamorphs. The adult dragonfly is eaten by a frog, which becomes a new host for the adult parasite. Wash rinse repeat.
A simple lifecycle would have the parasite living for at least one stage of its life-cycle as a parasite of a host, and the rest free-swimming. So we need to choose the most likely host for our simple parasite. I choose the frog as the likeliest host. The adult parasite can live the life of luxury, just pumping out egg after egg. The dragonfly merely acts as a transporter between snail and frog, and the snail, while possible, just doesn't seem as likely. But I could be wrong.
So, we start out with adult parasite in the frog, which excretes eggs and ingests free-swimming larvae to complete the cycle.
Now, snails enter the picture. Initially assume they can digest the eggs. What happens if the parasite evolves a way to survive being ingested by the snail? Descendants of that parasite are now more likely to survive than those that don't have that ability. Sometime later, the parasite evolves the ability to not only survive ingestion, but to parasitize the snail. Now the parasite has to devote less resources to getting food while inside the snail and gains an advantage. What do you know, we've now gone from one host to two. Adult larvae lives in frog, which excretes eggs, ingested by host snail, and then free-swimming larvae leave the sanil and infest a host frog.
Now being a free-swimming larvae makes it somewhat difficult to infest a frog, because you aren't high on the dinner menu. A larvae that can attach itself to something a frog likes to eat is much more likely to find a host frog.
And now you have a complex, three-host life-cycle.
Of course, this leaves a whole lot of questions to be answered. But these questions are not quite so hard to answer, and our knowledge of biology allows us to formulate experiments to test these tentative solutions.
That, my friends, is critical analysis.
Huh, it's no longer listing my name. I guess I'll have to abandon using OpenID.
The answer to how these parasites appeared is obvious: it is that I have no idea how they appeared, and niether does anyone else, if having an answer is understood in the properly scientific sense, i.e.,as being able to demonstrate a certain answer as highly probable, without relying upon mere speculation or arbitrary dogma. Darwin-buffs are habitually unable to distinguish between speculations and dogmas which they happen to prefer, and that which is scientifically demonstrable.
The speculative daydreaming of the Darwinists is really on the same plane as that of the Marxists, who always found that they could propose a Marxist explanation for anything that happened in history. The only problem was that they couldn't demonstrate that the explanation was right, or even that it was probably right. Still, they claimed that their theory was "science," and taught it as science in the old Soviet Empire. Now the Darwinists want to teach their doctrine as if it were "science," in every public school in the land.
So it's no suprise that quite a biologists who have been entranced by pseudoscientific Darwinist daydreaming, have also been infatuated by Marxism. Stephen Jay Gould was a Marxist, for instance.
"Darwin-buffs are habitually unable to distinguish between speculations and dogmas which they happen to prefer, and that which is scientifically demonstrable."
But it was Larry who said "How could the complex life cycle of the above parasite evolve by means of a random process when it is impossible to even imagine a process for such evolution?". All missingthepoint was doing was showing Larry is wrong by giving a plausible scenario for the evolution of such organisms.
As the original post made clear, work actually is being done to understand the evolutionary avenues that can produce such creatures - this is not just idle speculation of the sort ytou get from creationists, it is based on actual evidence.
Kevin Vicklund said...
>>>>>>> Huh, it's no longer listing my name. <<<<<<
That's fine with me, dunghill, because you are not welcome here. Your pettifogging trolling is bad enough, but your cyberbullying and cyberstalking are intolerable. Anyway, I recognized the name "missingthepoint" as being yours -- that's from the name of your blog.
missingthepoint said,
>>>>>> The adult parasite lays eggs, which the host frog excretes. <<<<<<
Where did you get that piece of information? The website I linked to says nothing about that.
The rest of your comment is mostly just a description of the life cycle instead of a description of a possible evolutionary pathway. The frog lung fluke's life cycle is very restricted -- for example, it doesn't just parasitize insects in general but parasitizes only dragonflies and damselflies, sometimes in a very specific way -- one species of frog lung fluke can only infect dragonflies by passively entering the rectal breathing apparatus. Discussions accompanying pictures on this webpage say,
Four representative frog lung flukes. Haematoloechus coloradensis and H. complexus are second intermediate host specialists where the cercaria can attach to any body region of aquatic arthropods. Haematoloechus parviplexus is a second intermediate host specialist and can only infect dragonfly (sic) by passively entering the rectal breathing apparatus, whereas H. longiplexus is intermediate in its host specificity and can infect dragonflies as well as damselflie.(sic)
-- and --
Dragonfly rectal breathing: The typical rout of infection for the cercaria of Haematoloechus parviplexus. H. longiplexus is intermediate in its host specificity and can infect dragonflies as well as damselflies. Cercariae of this species attach to the anal gills of damselflies and enter the rectum. The metacercaria of H. longiplexus is also unencysted!
"Where did you get that piece of information? The website I linked to says nothing about that."
It's obvious from your diagram.
"... one species of frog lung fluke can only infect dragonflies by passively entering the rectal breathing apparatus."
Well, dang! What more proof do we need? Who but a purposeful, loving Intelligent Designer could (or would) come up with such a scheme?
It's odd that these Darwin-buffs are unable to learn that although an "intelligent designer" has to be somewhat intelligent and purposeful, it doesn't necessarily have to be loving, powerful, supernatural, or whatever. And there doesn't have to be only one "designer:" there might be multitudes of intelligences involved.
Perhaps these guys really are addicted to the idea that ID is a plot hatched by Christians to get Adam and Eve, somehow, into science classes? And that's what accounts for their inability to understand ID as a concept?
This comment has been removed by the author.
"It's odd that these Darwin-buffs are unable to learn that although an "intelligent designer" has to be somewhat intelligent and purposeful, it doesn't necessarily have to be loving, powerful, supernatural, or whatever. And there doesn't have to be only one "designer:" there might be multitudes of intelligences involved."
Besides being no more appealing than chaos, this narrative fails Occam's Razor.
>>>It's odd that these Darwin-buffs are unable to learn that although an "intelligent designer" has to be somewhat intelligent and purposeful, it doesn't necessarily have to be loving, powerful, supernatural, or whatever. And there doesn't have to be only one "designer:" there might be multitudes of intelligences involved.
Perhaps these guys really are addicted to the idea that ID is a plot hatched by Christians to get Adam and Eve, somehow, into science classes? And that's what accounts for their inability to understand ID as a concept?<<<
I think the problem is that, if you genuinely remove all traces of religion from ID, going by what has been said by various people, including yourself, this is what you get as a proposed theory:
An unknown designer, or possibly designers, of unknown nature, designed and created either all life or only particular aspects of life on Earth, using an unknown method, at an unknown point in time in the past, for an unknown purpose.
Coupled with the vagueness of the so-called 'theory' is the fact no-one has come up with a single shred of solid evidence to support any part of the above (simply arguments from incredulity/ignorance), far less the whole thing, and the fanatical way evolution, or 'Darwinism', as IDists like to call it, is attacked, and it becomes clear that promoting ID on the strength of it's 'science' is, at best, a sign of extreme levels of ignorance and naivete on the part of the scientists doing so. However, most people simply cannot believe these scientists could be that ignorant and naive, so they go for the alternative explanation of pushing it as a smokescreen for religion.
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