Posted on 06/17/2003 7:05:07 PM PDT by Pharmboy
H. E. Hoekstra
Evolution has allowed some rock pocket mice,
pictured on light and dark rocks, to produce
distinct fur that helps disguise them.
In the deserts of the Southwest, among the towering saguaros and the spiny cholla cactuses, rock pocket mice hop and dash in search of a meal of seeds. But while these mice may seem to scamper haphazardly across the desert floor, their arrangement in nature is strikingly orderly.
Nearly everywhere these mice are sandy-colored, well camouflaged as they scurry across beige-colored outcrops. But in some areas, ancient lava flows have left behind swaths of blackened rock. There the same species of rock pocket mouse has only dark coats, having evolved an entirely distinct and, for their surroundings, equally well-disguised pelage.
Now, in a recent study in The Proceedings of the National Academy of Sciences, researchers report identifying the gene responsible for the evolution of dark coat coloration in these mice, pinpointing the DNA sequence changes that underlie this classic story of evolutionary change, the cute and furry counterpart to the famous case of the peppered moth.
Researchers say the study is the first documentation of the genetic changes underlying an adaptive change where the evolutionary forces were natural. Scientists point out that other well-known cases involve evolution caused by humans; some have suggested that those changes may be atypical of natural evolutionary change, since they have typically involved intense, directed pressures destroying most of a population, like the spraying of pesticides or the application of antibiotics.
"This work is very important," said Dr. Mike Majerus, an evolutionary geneticist at Cambridge University, who was not part of the study. "Here man is just not involved. The sandy and lava flow substrates are entirely natural phenomena."
Other well-studied examples of human-driven adaptive change include the evolution of pesticide resistance in insects after widespread spraying and the increase in the numbers of dark-winged forms compared with light-winged forms of the peppered moth in the United States and England after industrialization turned air sooty and polluted.
Dr. Michael W. Nachman, a population geneticist, along with colleagues at the University of Arizona, Dr. Hopi E. Hoekstra and Susan L. D'Agostino, studied mice living on Arizona's Pinacate lava flow in Arizona and on light-colored rocks nearby. The researchers were able to take advantage of decades of meticulous work in which other scientists identified some 80 genes that affected coat color in laboratory mice.
On close examination, the light-colored rock pocket mice could be seen to have a type of hair coloration similar to standard, sandy-colored laboratory mice. In this pattern, known as agouti, the hair is black at the base, yellow in the middle and black again at the tip. The dark-colored rock pocket mice had completely dark hairs.
Researchers knew that mutations in a few well-known coat coloration genes in laboratory mice could cause such complete darkening of the hair, and they began by looking at two genes known as agouti and Mc1r. When they looked at DNA sequences in light and dark mice, changes in the agouti gene did not appear to be associated with light-colored fur versus dark-colored. Still, the researchers found that a certain cluster of mutations at Mc1r could be found in every dark-colored mouse.
"It's a textbook story," Dr. Nachman said. "Now we have all the pieces of the puzzle together in a natural setting."
Dr. Nachman noted that while the new study points to the Mc1r gene as the key to turning mice dark on the Pinacate lava flow, the team also found that dark mice on another lava flow in New Mexico did not share those mutations.
"So the same dark color has evolved independently in the two different populations," he said, "through different genetic solutions to the same evolutionary problem." Dr. Nachman said changes in another gene, perhaps the agouti gene, could be responsible for dark coloration in the New Mexico's Pedro Armendaris lava flow.
One could easily imagine that coloration would be of no consequence to the rock pocket mice, as they are nocturnal, darting about under the desert night sky. But researchers, working early in the last century, released light and dark mice on light and dark backgrounds in an enclosure at night and found that owls, a major predator of mice, could easily spot a mouse on a mismatched background.
Dr. Nachman noted, however, that these early researchers did not use rock pocket mice in their study, but instead used a species in which the dark and light forms were actually much less distinct.
As a result, he said, "we think the owls are discriminating even more strongly in our species." He said tiny bits of rock pocket mouse were often found in pellets at owl roosts.
Dr. Majerus said many kinds of animals showed light and dark forms, from deer mice to squirrels and chipmunks. There are even black ladybugs.
"A lot of the dark forms show an association with a particular type of substrate they're on, or the frequency of burning and charring of the trees in the woodlands," he said, noting that it would be interesting to do genetic studies in other animals, to see how many genetic solutions these other animals have come up with to turn dark.
But while many dark forms are abundant and can be studied at scientists' leisure, Dr. Majerus said that of the peppered moth was slowly disappearing.
So while there is nearly unanimous praise for the increasingly clean air in industrialized regions of the United States and Britain, there may be, at least for some scientists, a downside. "We've got about 15 or 16 years," Dr. Majerus said, "before those black forms, if they continue to disappear at the current rate, disappear completely."
Not at all. Whether nor not Haeckel's drawings were precise by modern standards matters not one bit. 'plusone' seemed to be making the point that minor micro-evolutionary anatomic variation such as beak size and shape in a finch is unrelated to major macro-evolutionary anatomic differences like the presence or absence of wings. I disagree. It is a difference of degree and not kind. Different types of vertebrate embryos are indistinguishable from each other early on, unless chromosomal and genetic analysis is performed. Change one gene sequence, you get a bigger beak. Change another, or a few more, and you get no wings, or grow a leg from out of the forehead. What basis is there to think that these are different processes?
-ccm
When it makes them invisible to hunters?
Hmmm.... well, you know what I mean.
I will "add or correct" this...
A "bunch of micros" do not make a Macro. "Micro-Evolution" is simply adaptation within the existing gene pool of an established species. If the existing gene pool of desert mice allows for both Tan-colored Mice and Dark-colored Mice, then you should expect the Tan-colored Mice to dominate within their environment, and the Dark-colored Mice to dominate within their environment.
That's Natural Selection, which is entirely Scientific.
It's an entirely different matter to drop the Desert Mice -- Tan, or Dark -- into the middle of the Pacific Ocean and expect them to survive. Why? Because Desert Mice don't have Gills. Micro-Evolution -- adaptation within the existing gene pool -- runs into a Brick Wall when asked to "adapt" to an environment for which the Organism in question simply does not have the necessary Genes.
In order to alter the "adaptation-potential" for the species in question, to allow adaptation to environments for which the Organism in question simply does not have the necessary Genes, it becomes necessary to invoke Macro-Evolution -- a fundamental alteration of the Genetic Code of the organism itself. Because Micro-Evolution -- adaption within the existing gene pool -- just won't cut it. You can propose all the Micro-Evolutionary changes you want, adaptions within the existing gene pool, and Desert Mice still can't swim the Pacific Ocean without Gills.
In order for Desert Mice to have Gills, the Genetic Code of the organism itself must change. Micro-Evolutionary adaptions within the existing gene pool won't cut it.
IOW, a bunch of "Micros" do not add up to a "Macro". Micro-Evolution is simply adaptation within the existing gene pool. If you want to change the adaptability of the Organism to encompass environments not currently survivable within the Species Gene Pool, you have to alter the Genetic Code of the Organism itself.
Which is why, in both Neo-Darwinism and Punctuated Equilibrium, you need Genetic Mutation -- to alter the Genetic Code of the Organism itself.
Except that Genetic Mutation doesn't, well, work -- somewhat akin to throwing a wrench into a finely-tuned engine, it tends to create more problems than it solves.
Except that Genetic Mutation doesn't, well, work -- somewhat akin to throwing a wrench into a finely-tuned engine, it tends to create more problems than it solves.
TENDS to create more problems than it solves, yes. But that's different than saying mutations ALWAYS create more problems than they solve, which they clearly don't. (See: Examples of beneficial mutations.)
This article is obviously a hoax. There are no cute mice.
"Gene twisting" has such a ring to it, so much more picturesque than the terms scientists use, e.g. "point mutation", "alternate intron/exon splicing", etc.
No, they don't.
Perhaps the only thing more annoying than a Creationist who does not understand the debate (which is, sadly, to be expected), is an Evolutionist who does not understand the debate (which, given the current state of Publik Skooling, is ALSO to be expected, I suppose).
And listen up, Grasshopper -- as evidenced by the laughably-ridiculous nonsense you posted above, you clearly DO NOT understand the debate.
Let's imagine an Organism with the Genetic Code (and therefore, the adaptability-potential) to adapt to Biomes A, B, C, and D. And let's say that you drop this Orgamism into Biome E. It's ALWAYS going to Die. All the "Micro-Evolutionary" changes, within its existent Gene Pool, from A to D and back again won't save it... it does not even possess the genes to survive in Biome E, whether the "A" subspecies or the "B" variant or the "C" variant or the "D" variant. Look at the Human Species, for example -- we can be "Caucasoid" (white) or "Negroid" (black) or "Mongoloid" (yellow-red) or "Australoid" (brown), but we don't have gills. All adaptations within the existent Homo Sapiens genetic code (white, black, yellow, red, brown, whatever) are "micro-evolutionary" adaptations -- differentiation within the existing Genetic Potential of the Species. But in order for Humans to have GILLS -- if we wanna be "Aqua-Man of Atlantis", or what have you -- we require a fundamental alteration of the Human Gene Pool itself -- Genetic Mutation. "Micro-Evolutionary" adaptations within the existing Gene Pool will always run into a Brick Wall -- whether white, black, yellow, red, or brown, HUMANS DON'T HAVE GILLS.
In order for Humans to have Gills, "Micro-Evolutionary" adaptations within the existing Gene Pool just will not cut it -- you need a fundamental alteration of the Human Gene Pool itself -- Genetic Mutation.
Good grief, here I am a Fundamentalist Six Day Creationist, and I am having to explain f*cking basic evolutionary genetic science to a professing "evolutionist".
If there is a better evidence of the failure of Publik Skooling in America, I can't imagine what it would be.
What is that old saying? Something like, a journey of a thousand miles starts with a single step? Evolution is exactly like that, one little step after another, until an organism results that is no longer the same species as the original organism.There is a certain amount of 'free play' within the genetic structure
I can't imagine what you're referring to; what is the nature of the "free play"?
Every time a C/G base pair mutates into an A/T base pair, I would say new genetic information is created. DNA is a highly mutable substance; annoying for a molecular biologist trying to engineering new DNA molecules, but very consistent with the whole evolution thing.
Meaning that science only advances at a rate marginally faster than that of evolution. It's frustrating that my first (and only) scientific article essentially describes a negative result (examined, of course, in great detail) and was only published because it refutes the work of a leader in my field. Once upon a time, I thought I'd go into science and do something brilliant and significant...well, I'm wiser now...
Nice link, but it reads like a lot of people arguing with eachother. If I was interested in that, I'll handle my affairs personally, and argue the points myself.
Tell you what -- since you admit that "Genetic Mutation TENDS to create more problems than it solves, yes", howzabout you intrigue me with some example which conform to the following criteria:
Best, OP
I think you could use some definitions here. The term "genetic code" specifically refers to the codons that code for amino acids in a protein, e.g. the three bases "ATG" code for methionine, "CTG" for leucine, "TAA" for STOP, etc. This code is mostly invariant across all species; in individual cases, a messenger RNA can be mutated to recognize a different codon for a particular amino acid, but in general, new code is not being created. The theory of evolution, while being an excellent theory with everyday applications for molecular biologists, geneticists, biochemists, etc., mostly deals with events occurring after the genetic code developed.
I did not say that there is no evidence of new genetic sequences being generated in modern times.
Not only are they being generated constantly in nature, but scientists are obsessively rearranging and mutating DNA all the time. (It keeps us off the streets and out of trouble.)
Stellar objects, I presume? Do you store them in your freezer?
How early on? I've seen many pictures of mouse embryos; they look like mice. Ditto for chicken embryos (except they look like chickens, not mice).
What a disgusting misrepresentation of evolutionary theory. If an organism doesn’t have the necessary genes to adapt to its environment it dies, true. Mice thrown into the sea would no more evolve in response to the sea than you would evolve to a bullet fired at your head. Your entire post ignores basic genetics, in that fundamental changes to the genome occur during reproduction. After fertilization of the first cell, the genome of the individual is virtually set into stone.
Fish originally evolved in freshwater, then later evolved to living in seawater. Freshwater fish do not have the genes necessary to live and reproduce in full seawater. However their freshwater genes do allow them to survive for a time in slightly brackish water, something they might experience if they swam too far down the river towards the ocean. Through random mutations some of the offspring of these primordial freshwater fish were able to tolerate water of a slightly higher salinity. This gave them a selective advantage in that they could swim farther down the river than full freshwater fish. They could then exploit the new food sources in these newly accessible waters. Some of the offspring of these fish could tolerate water of even higher salinity because they possessed mutations that improved upon their parents’ genes. Repeat this process many times and you end up with fish that can take the full force of ocean saltwater.
In order to evolve to some hostile new environment, the organism must have the genes to survive in that kind of environment to some capacity. It may not survive well at first, but after many generations of selection, the offspring will survive better. Alternatively it could first evolve to a less extreme version of the hostile environment and then from there evolve again to a more demanding version, like in my example. Evolutionary theory never says that an organism will always adapt to an environment. A critical part of the theory consists of extinction, when the stressors are too great and all individuals in the population die without producing offspring. Only your strawman theory of evolution requires that mice thrown into the sea evolve.
Maybe because evolutionists keep changing the theory constantly?
Let's see you tell us all what THE theory of evolution says before you criticize what others say about it.
Every time evolutionists are asked for proof they give the very same unscientific article which has been thoroughly debunked in A Critique of 29 Evidences for Macroevolution as well as on several threads right here on FreeRepublic. There is tons of Evidence Disproving Evolution which evolutionists constantly ignore and which unlike their articles, is based on solid scientific facts.
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