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.”
But the child is still a child. I don't understand why you folks have so much difficulty with understand that a small dog is still a DOG, and a mutated child is still a CHILD. It has not evolved into a different SPECIES.
> I have written repeatedly that the theory of evolution is an exercise in...IMAGINATION.
QAll science is based on the ability to imagine. That's the first step in producing a hypothesis. Sadly, too many people either cannot imagine, and thus stick with the dogmas that were pounded into them, or they cannot constrain their imagination within reality, and become New Agey goofballs. Science lies in between.
> It is in fact, ANTI-science
Wrong. Imagination is vital to science. Without it, no progress is possible.
> a small dog is still a DOG, and a mutated child is still a CHILD. It has not evolved into a different SPECIES.
Not yet...
Today a child. Tomorrow a child. The next day a child....
So, where does the adult come from?
I don't know. My problem is that we have no proof of what those things are. Just because something "looks" like something else does not mean that one thing came before or after the other or that they are related. All it means - literally - is that one thing "looks" like another or that they have traits on common. The only way that evolution might be proven is to show the process in action, which we have not been able to do. If evolution is an ongoing process, then at some point within our recorded history, some species somewhere should be recorded as having mutated into another completely different species - if not in one pass then at least over a few generations. There is no such record that I am aware of. So as far as I can tell, evolution, to whatever extent it exists, is not a regular, on-going process.
Don't be taken in by assumptions. Because one thing looks like or has traits in common with another, does not mean they are related or have any common ancestor.
My problem with evolution in a nutshell is that its adherents refuse to recognize that it is a belief system which they stick to with a fervor which prevents the possibility of conceiving error or of amending a belief or changing it completely. I remember how doctors and scientists fought so long and hard against the simple process of doctors washing their hands after examining corpses and before delivering babies. That was a major revolution in hygiene which many members of the medical profession fought ardently. It went against their "belief" system. I have no tolerance for belief systems in science. Theories are fine, but subject to change always until there is physical proof.
from a human. a human is a human is a human. a child is not a different species from an adult and a small dog is not a different species from a large one.
Imagination is NOT science. It is helpful to science certainly but imagination is equally useful in poetry, art, sculpture or even cooking. Science is based on proof, not on imagination. You cannot postulate an entire theory of creation on imagination and call it science. That is both ridiculous and factually incorrect.
Most theories are like that. You use your imagination to try to explain the facts. The theory of evolution has plenty of facts, but not all of all the facts. And again, most theories are like that.
I have to go, folks, so I'll see you all later. Just so you don't think I'm ducking out on the debate, lol.
There is only one God.
Your missing the point. Evolution predicts that its own processes occur so slowly, that you wont find any evidence for the evolution. Rather than admit that no one observed this species turning into that species, its easier to arrange some similar looking fossils into perceived evolutionary order and say "There, that looks good ... we have a series." Slap the ole' good science seal of approval and you have your airtight "proof."
Its like taking a tangerine, an orange, and a grapefruit and putting them in size order and claiming evolution has occured.
Imagination is NOT science. Science is ONLY demonstrable proof - a result that can be reproduced or predicted. Otherwise psychics would be our greatest scientists.
A shark is a shark is a shark. Those are not different species. They are still SHARKS, lol. Send me a flare when a shark turns into a ring tailed baboon.
> Those are not different species.
Yeah, good one! And humans and chimps are the same species (a primate is a primate is a primate)! And housecats and tigers and puma are the same species! And hawks and pigeons and albatrosseses are the same species!
Biology class with you as teacher would take, what... fiften, twenty minutes?
If I tell you what it is will you stop trying to beat science over the head with how little of it you personally know or understand? Here's a web page describing that when you go back down the tree of life following the carnivore branch in the fossil record to where you don't see cats or dogs or bears or weasels or civets or raccoons anymore, you get to a thing called a miacid. This not only is the common ancestor of the later diversified forms, but it looks surprisingly like the last common ancestor (called a condylarth) of the ungulates (horses, deer, etc.).
This similarity as one looks back in time between carnivores and ungulates is a prediction of evolution. Being mammals, these groups also have a common ancestor. The fossil record indeed shows this.Figure 10. Comparison of skulls of the early ungulates (condylarths) and carnivores. (A) The condylarth Phenacodus possessed large canines as well as cheek teeth partially adapted for herbivory. (B) The carnivore-like condylarth Mesonyx. The early Eocene creodonts (C) Oxyaena and (D) Sinopa were primitive carnivores apparently unrelated to any modern forms. (E) The Eocene Vulpavus is a representative of the miacids which probably was ancestral to all living carnivore groups. (From Vertebrate Paleontology by Alfred Sherwood Romer published by The University of Chicago Press, copyright © 1945, 1966 by The University of Chicago. All rights reserved. This material may be used and shared with the fair-use provisions of US copyright law, and it may be archived and redistributed in electronic form, provided that this entire notice, including copyright information, is carried and provided that the University of Chicago Press is notified and no fee is charged for access. Archiving, redistribution, or republication of this text on other terms, in any medium, requires both the consent of the authors and the University of Chicago Press.)
We see this convergence in case after case. As you trace birds and dinosaurs back, they grow together until there are specimens whose classification is controversial. The same thing happens with mammals themselves, where they branch from reptiles. That's what evolution says we should find and we do.
> Science is based on proof, not on imagination.
Without the imagination, the proof would not only never be found, it'd never be sought. Hmmm... rather like Creationism...
> There is only one God.
...
... and Muhammad is his prophet.
Dogs and wolves are in the process of speciating far enough apart so as to be unable to interbreed. Subspecies of dogs also appear to be in the process of speciating to a degree so as to make interbreeding impossible.
But here they aren't using the same names anymore. That means you can play "Guess which banned militant idiot THAT clueless noob is?"
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