Posted on 05/31/2005 12:03:06 PM PDT by PatrickHenry
In a stunning example of evolution at work, scientists have now found that changes in a single gene can produce major changes in the skeletal armor of fish living in the wild.
The surprising results, announced in the March 25, 2005, issue of journal Science, bring new data to long-standing debates about how evolution occurs in natural habitats.
“Our motivation is to try to understand how new animal types evolve in nature,” said molecular geneticist David M. Kingsley, a Howard Hughes Medical Institute investigator at the Stanford University School of Medicine. “People have been interested in whether a few genes are involved, or whether changes in many different genes are required to produce major changes in wild populations.”
The answer, based on new research, is that evolution can occur quickly, with just a few genes changing slightly, allowing newcomers to adapt and populate new and different environments.
In collaboration with zoologist Dolph Schluter, at the University of British Columbia, Vancouver, Canada, and Rick Myers and colleagues at Stanford, Kingsley and graduate student Pamela F. Colosimo focused on a well-studied little fish called the stickleback. The fish — with three bony spines poking up from their backs — live both in the seas and in coastal fresh water habitats all around the northern hemisphere.
Sticklebacks are enormously varied, so much so that in the 19th century naturalists had counted about 50 different species. But since then, biologists have realized most populations are recent descendants of marine sticklebacks. Marine fish colonized new freshwater lakes and streams when the last ice age ended 10,000 to 15,000 years ago. Then they evolved along separate paths, each adapting to the unique environments created by large scale climate change.
“There are really dramatic morphological and physiological adaptations” to the new environments, Kingsley said.
For example, “sticklebacks vary in size and color, reproductive behavior, in skeletal morphology, in jaws and teeth, in the ability to tolerate salt and different temperatures at different latitudes,” he said.
Kingsley, Schluter and their co-workers picked one trait — the fish's armor plating — on which to focus intense research, using the armor as a marker to see how evolution occurred. Sticklebacks that still live in the oceans are virtually covered, from head to tail, with bony plates that offer protection. In contrast, some freshwater sticklebacks have evolved to have almost no body armor.
“It's rather like a military decision, to be either heavily armored and slow, or to be lightly armored and fast,” Kingsley said. “Now, in countless lakes and streams around the world these low-armored types have evolved over and over again. It's one of the oldest and most characteristic differences between stickleback forms. It's a dramatic change: a row of 35 armor plates turning into a small handful of plates - or even no plates at all.”
Using genetic crosses between armored and unarmored fish from wild populations, the research team found that one gene is what makes the difference.
“Now, for the first time, we've been able to identify the actual gene that is controlling this trait,” the armor-plating on the stickleback, Kingsley said
The gene they identified is called Eda, originally named after a human genetic disorder associated with the ectodysplasin pathway, an important part of the embryonic development process. The human disorder, one of the earliest ones studied, is called ectodermal dysplasia.
“It's a famous old syndrome,” Kingsley said. “Charles Darwin talked about it. It's a simple Mendelian trait that controls formation of hair, teeth and sweat glands. Darwin talked about `the toothless men of Sind,' a pedigree (in India) that was striking because many of the men were missing their hair, had very few teeth, and couldn't sweat in hot weather. It's a very unusual constellation of symptoms, and is passed as a unit through families.”
Research had already shown that the Eda gene makes a protein, a signaling molecule called ectodermal dysplasin. This molecule is expressed in ectodermal tissue during development and instructs certain cells to form teeth, hair and sweat glands. It also seems to control the shape of - bones in the forehead and nose.
Now, Kingsley said, “it turns out that armor plate patterns in the fish are controlled by the same gene that creates this clinical disease in humans. And this finding is related to the old argument whether Nature can use the same genes and create other traits in other animals.”
Ordinarily, “you wouldn't look at that gene and say it's an obvious candidate for dramatically changing skeletal structures in wild animals that end up completely viable and healthy,' he said. "Eda gene mutations cause a disease in humans, but not in the fish. So this is the first time mutations have been found in this gene that are not associated with a clinical syndrome. Instead, they cause evolution of a new phenotype in natural populations.”
The research with the wild fish also shows that the same gene is used whenever the low armor trait evolves. “We used sequencing studies to compare the molecular basis of this trait across the northern hemisphere,” said Kingsley. “It doesn't matter where we look, on the Pacific coast, the East coast, in Iceland, everywhere. When these fish evolve this low-armored state they are using the same genetic mechanism. It's happening over and over again. It makes them more fit in all these different locations.”
Because this trait evolves so rapidly after ocean fish colonize new environments, he added, “we wondered whether the genetic variant (the mutant gene) that controls this trait might still exist in the ocean fish. So we collected large numbers of ocean fish with complete armor, and we found a very low level of this genetic variant in the marine population.”
So, he said, “the marine fish actually carry the genes for this alternative state, but at such a low level it is never seen;” all the ocean fish remain well-armored. “But they do have this silent gene that allows this alternative form to emerge if the fish colonize a new freshwater location.”
Also, comparing what happens to the ectodysplasin signaling molecule when its gene is mutated in humans, and in fish, shows a major difference. The human protein suffers "a huge amount of molecular lesions, including deletions, mutations, many types of lesions that would inactivate the protein," Kingsley said.
But in contrast, “in the fish we don't see any mutations that would clearly destroy the protein.” There are some very minor changes in many populations, but these changes do not affect key parts of the molecule. In addition, one population in Japan used the same gene to evolve low armor, but has no changes at all in the protein coding region. Instead, Kingsley said, “the mutations that we have found are, we think, in the (gene's) control regions, which turns the gene on and off on cue.” So it seems that evolution of the fish is based on how the Eda gene is used; how, when and where it is activated during embryonic growth.
Also, to be sure they're working with the correct gene, the research team used genetic engineering techniques to insert the armor-controlling gene into fish “that are normally missing their armor plates. And that puts the plates back on the sides of the fish,” Kingsley said.
“So, this is one of the first cases in vertebrates where it's been possible to track down the genetic mechanism that controls a dramatic change in skeletal pattern, a change that occurs naturally in the wild,” he noted.
“And it turns out that the mechanisms are surprisingly simple. Instead of killing the protein (with mutations), you merely adjust the way it is normally regulated. That allows you to make a major change in a particular body region - and produces a new type of body armor without otherwise harming the fish.”
No. We talk talk about reasonable things, like possibility of gradual evolution. You talk about stupid things like a porpoise developing legs and walking around downtown Boston.
These are very much the reasons why the IDists have not been able to show it statistically improbable.
"and can’t reproduce the event in the laboratory,
Yet! That it hasn't been done does not equate to can't be done. In that respect it does not serve the anti-evolution faction. They have no more an idea of its probability than any.
"and can’t show it to be statistically probable.
See above
"All valid reasons as to why not. Why then are you so very sure that it happened at all?"
Because of a convergence of information gleaned from a ton of different sources.
My Question: "What's a spider agave? Or a tykva? Or a bird agave? Or a rossette plant?"
Your Answer: "These are all....PLANTS. so what?"
Um, no, they are not. They are imaginary creatures exhibiting the traits of both plants and animals, invented (not by me) for an imaginary planet. They are fascinating because they play directly off of observed niche adaptations that make your favorite catch phrase more likely to be "a fish is a mammal is a bird."
Not unlike, say, a walking catfish or a porpoise or a penquin.
Indeed, what we can imagine is often less unlikely than what we observe. Morphology can be very deceptive. You say that "a wooly mammoth is still recognizable as a type of elephant." What's a manatee recognizable as? Or a hyena?
You do not seem to be aware of how much simplifying is already going on.
Most of the scientists on these threads post for the lurkers and want to make the information accessible to those who might actually be interested in learning. I am continually amazed at their patience.
And, by the way, if you really wanted to learn, you would find a way to do so.
Could you explain to me what genetic information is? I've heard many creationists and IDists use it the term but I don't quite understand its use or necessity.
Darby, I just checked back to see what they're ranting about now, and of course, they refuse to explain anything in layman's terms because we are all just too stupid or lazy to learn. It's our fault, naturally. And they wonder why so many people refuse to accept their theory - it's because they can't even explain it in simple terms themselves. All they can do is insult and call names. Public relations is not their strong point - nor teaching, I guess. It's fine with me, as I say, I think they're all full of moonshine anyway. I don't want to debate with them myself any longer as I quickly tire of religous fanatics, of which these folks are just another breed. I wish they could see themselves for the obnoxious, narrow minded, hypocritical fanatics that they are.
Just like those 16th century Jesuits.
Oh - incidentally, as I was unfamiliar with these plants - I assumed they were plants - I googled them to come up with descriptions. I'm sure you think you were very clever in coming up with fake plants - maybe you could have a career in designing sets for Star Wars. It's irrelevant to the argument, however. Moreoever, there actually ARE plants right here on earth that do eat flesh. Venus fly-traps for one, which reminded me of the Google descriptions I read. But you know what...a plant is still a plant is still a plant.
I thought it was science that determined what a theory is, not you? Am I wrong?
The ToE states that through natural selection and genetic drift (and other mechanisms) organisms change in such a way that they, if traced back far enough, share a common ancestor with other organisms. It says nothing about a cat turning into a dog.
I'm done debating with you folks. I've said everything that I think can be said on the subject - from my perspective anyway, and I'd just recommend that anyone who is so inclined go back and read my posts. If I keep posting, I'll just keep repeating myself over and over again, and that is pointless.
Normally an honest sceptic or critic will try to do independent research on the topic they are sceptical about or critical of.
If you don't like the presentations here there's always google.
Of course an opponent, as opposed to a sceptic or critic, won't bother.
What I was obviously referring to is that there no proof that any species has ever turned into another COMPLETELY different species, even in stages. There is no proof geologically, biologically or through direct observation. You are taking animals that appear to be similar to each other and postulating a relationship that exists solely within your own framework. Someone else who is not invested in the ToE might come to completely different conclusions. Your framework dictates the outcome. You find what you are "looking" for.
I use cat/dog, whatever to illustrate the point. I realize it is a simplification, but not everyone reading these posts is a microbiologist, and sometimes arguments need to be drilled down to their most basic or fundamental components. In short, to directly answer your point - there is NO proof of any common ancestor shared by all of these various species going back to the primeval ooze, nor of any lower order mutating into a higher order, or a completely different species (i.e., a cat turning into a dog rather than a tiger), nor any proof that this is an on-going process as nothing of this nature has been observed in recorded history. All that has been observed are mutations from one type of plant to another type of plant, or one type of animal into another animal that is obviously from the same general family. A tiger is still a cat. A wooly mammoth is still a type of elephant. I don't know what a hyena might be related to, but it doesn't matter anyway unless it decides at some point to turn into something other than a hyena. Maybe it's ALWAYS been a hyena or hyena like creature.
This will have to be my last word on the subject as I'm just going to be repeating myself.
You are postulating an incorrect reason for his being 'hounded out of academia'. You also chose one small portion of his many ideas, that just happens to sound correct, as an accurate example of his theories. The truth is, his ideas were not well founded, nor backed by current science knowledge. Do a google on his theories to find out why he is regarded as poorly as he is.
You are cherry picking.
When I googled tykva the first hit I got clearly indicated that it was imaginary.
Just thought you'd like to know.
The nice thing about the 16S RNA tree is that that gene is not exchanged, so there really is a single common ancestor for all 16S RNA.
You can find a number of 16S RNA genes on this link and construct a tree from them yourself, if you don't believe me. There is also an online link to the full 16S tree of life, which contains at least 10,000 different sequences and is growing every day.
Warning: the full 16S tree is huge!
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