Researchers Trace Evolution to Relatively Simple Genetic Changes

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.”

You are exemplifying the very arrogance of which I wrote. Stop talking down to me. There is no "science" on your side as you can PROVE nothing. You have no proof. You have a theory. It may be a good one, but others have theories too and frankly they have as much proof, or lack of proof as you do.

The scientific method is quite clear and is the same one that has been used for hundreds of years. A scientific fact is something that is observable, or that can be proven with consistent results by experiement or which has a consistently predictable result. Gravity for example. We know SCIENTIFICALLY that gravity exists because we are able to experiment upon it consistently and see consistent physical results. We know that the apple always falls down from the tree and not up. These are all FACTS. There are NO FACTS behind evolution - only suppositions and assumptions. That's what makes it a THEORY. You folks don't seem to understand what the difference between a scientific fact and a theory is.

You asked for an human observed example of speciation. I provided that.

Of course no human has been able to observe a lizard turn into a bird because it happens in many, many steps. Even speciation can take thousands of years. No animal has turned into a completely different animal in one generation. And no proponent of evolution has ever argued that it happens instantly. You have placed that false argument in the mouths of your opponents to further your own lack of argument.

And so you have no PROOF. You cannot create an experiment to prove evolution - real evolution, not some mutation within a plant or animal - but a genuine change to a creature that would be recognizable as a totally different species. You cannot predict such a thing. You don't understand how it happens. You cannot explain the mechanics of it. You have no direct observation of it. You have none of these things that go into making a scientific fact. What you have is a theory. That's all. The problem with enshrining a theory is that it actually prevents the progression of science because it prohibits the possibility of being wrong, or of radically revising the theory. It becomes an article of FAITH.

Incidentally, what you're saying about observation is not true. Certainly no human may have witnessed the metamorphosis of a specific species into another species within a given time span as (if evolution is correct) it might take millennia. However, the larger point is that if evolution is a general and on-going process SOME species SOMEWHERE would have mutated into another species at some point within recorded human history. Someone would have noticed a grasshopper turning into something resembling a bird. I know of NO observations by anyone within recorded history of any species transforming into anything other than some variation of what the original species was. A plant is a plant is a plant. A fish is a fish is a fish, etc. Thus, this cannot be an on-going process as some species SOMEWHERE even right NOW would be evolving. Or are you saying that evolution only occurred a convenient several million years ago and no longer occurs?

Lol, apologies accepted. This topic gets overheated unfortunately and it's easy for every one to get arrogant, probably even me. Hopefully I am not too obnoxious either :) I am not necessarily totally against evolution (although I don't believe in gradual evolution in general), however I am very much against the enshrinement of theories that have no proof or that cannot be proven, for whatever reason.

Small beneficial mutations are proof of macroevolution. Millions of these mutations over many years cause speciation. Speciation means that the descendents of the same species can no longer interbreed and produce offspring.

And a human did observe speciation in the example I gave you.

And geneticists have explained exactly how genetic recombination occurs. And how errors in genetic recombination occur.

I love it when you scientists turn into 2 year olds talking street jive when you don't have a cogent response. nanny nanny boo boo, you're a doo doo head. I'll tell you the way I told my 2 year olds. Saying it louder don't make it right.

quack quack.

I was enjoying the conversation until you de-evolved to your infantile ancestry. Or maybe the devil made you do it. More likely it was way past your bed time.

> Or He could have just snapped His fingers as He did with the Big Bang.

Then you;re suggesting that God is either a liar or a prankster. There's no other way to explain the geological and fossil records.

> Evolutionists will eventually be humbled about their little theories one way or the other.

Indeed. Evolution constantly turns out to be far more elegant, extravagant and universal than previously imagined.

Yes, I should definitely work on the tone of my posts if I ever want to convince anyone. I believe in evolution because I see random recombination often in my work with bacteria that I use to make large scale DNA preps of plasmids (circular DNA). I can extrapolate that when I multiply it by millions, billions of years. I can also tell that probably the majority of mutations are harmful to the organism. But some aren't. And when you take a small chage and multiply it by billions of years, you get big changes.

But yes, I can totally dig someone not wanting to have something shoved down their throat without asking a lot of questions. That's how I feel about most government policies.

Well we will have to agree to disagree. As I say, a plant is a plant is a plant. Perhaps our problem is semantics. When people refer to evolution, they are not generally thinking of the process by which variations within a division of the plant or animal world occur (such as variations or mutations of a flower). What they are really referring to is a change from a lower order of creature to a higher order of creature, particularly man, and the idea that all life descended from increasingly primitive creatures as we go back in time. When I say that there is no proof of evolution, I am not referring to the mutations within a species of flower, or animal such as a dog or cat that all people recognize. I am referring to the process by which primeval ooze produced amoebas that somehow became shrimp that somehow became fish, that somehow became frogs, that somehow became reptiles that somehow became mammals, that somehow became primates, that somehow became man. That is where the proof is lacking and where the argument lies.

Perhaps some day then, YOU will provide the proof and that will be what we need to solve the question. Thank you for being so reasonable in terms of recognizing the tone of the argument. Too many pro-evolution people fail to recognize that there are substantial holes in their theory that are very obvious to people who are not committed to the theory and particularly to the religious. Those holes have to be addressed and just insulting people or trying to ignore the holes is not going to win people to the pro-evolution side. I'm sure you'll go far with your work.

The evidence is in the fossil record that shows the gradual change in morphology. The other proof is that certain enzymes and proteins are conserved almost unchanged from bacteria to mammals. One example of conservation from bacteria to plants is hydroxyisobutyrate dehydrogenase. That's what my old boss was working on. He sequenced the DNA that coded for the enzyme, and he found the code in a chain of organisms from simple to complex. This suggests a common ancestry. Also, in your DNA there are large stretches of genes that don't code for anything any more because they are turned off. They had a purpose when your ancestor was something completely different.

More compelling evidence can be found in embryology. The human starts as one cell, becomes a group of cells, the group of cells becomes a fish-like organism, and then an amphibian like organism, and then it is almost indistinguishable from a mouse embryo, then it grows and loses a tail, and finally starts looking like a human. Ontogeny recapitulates phylogeny. Meaning the development of the individual resembles the development of the species.

I am referring to the process by which primeval ooze produced amoebas that somehow became shrimp that somehow became fish, that somehow became frogs, that somehow became reptiles that somehow became mammals, that somehow became primates, that somehow became man. That is where the proof is lacking and where the argument lies.

Indeed! Sometimes when we don't have the answers we are looking for it's best to just take some time out to pay respect to the Creator:

Sorry for butting in, but you seem to be of the conviction that (a) theories can be proven and (b) that theories graduates to 'fact'. I'd recommend that you google around a little and read up on the terminology of science. You see, theories are never proven (they can only be disproven, or falsified), and they don't ever graduate to 'fact' (when an explaination has reached the status of a theory, it cannot climb higher). Of course, scientific terminology can and do conflict with popular uses of some words, and that seems to be the problem in your case.

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