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."
The above shows the sophistry of evolution. On the one hand you admit that the coloring of the mice was selected from already existing genetic information in the species. Then you claim it is a mutation. One contradicts the other. All species have a wide genetic pool and all that selection does is decrease the size of the genetic pool of the species and this is not an advantage but a disadvantage. For example, if humans were to plant these places and change the land the genes for browness would no longer be in the genetic pool of these mice and they would dissappear. This is the problem with selection as an agency of evolution, it does not create, it destroys part of the genetic pool of the species and makes it less likely to survive when the environment changes again.
Whoohooo! Sorry I missed being there!
Why yes, we do..... in a very, very large one, with an almost uniform temperature of of 2.7 degrees Kelvin, and it's getting "bigger" every day........
;-)
Thus, this famous argument by the evolutionists actually supports the anti-evolutionists' position--which is that mutations are deleterious. The evolutionists need to think through their position a lot more carefully. The doctrine of natural selection actually supports the creationists' case.
By the way, the notion that microevolutionary changes (variation) can ever add up to macroevolutionary changes (speciation) has not been thought through very well at all by the evolutionists.
To illustrate: A person looking at bats and rats might be tempted to say that a bat is a rat with wings. That person might very well ask how this presuppositional rat (actually, just a bat, not a rat in any sense whatsoever, even if it looks "ratty") acquired these wings.
Since we know that microevolution (variation) occurs, he might very well assume that it just took a lot of microevolutionary changes to produce the wing. But this is impossible for the very reasons of natural selection. (The mainstream evolutionists are sure that this is not the case, because they doggedly refuse to question their presupposition! But they need to start facing the scientific issues more honestly, more objectively. See below.)
***
If we look at the bat's wing, it has the simplistic appearance of a flap of skin on a long, thin bone which reaches out from an upper body appendage somewhat like a rat's foreleg. But the question is, How did the "thumb" of the rat's foreleg develop this elongation and skin covering?
Or maybe I should say that this is the typical evolutionists' question. A better scientist would have asked, Did the "thumb" of the rat's foreleg develop this elongation and skin covering?
Anyway, if we assume that it did happen, and if we go on to ask ourselves how it did, we should notice that it didn't. But the diehard evolutionists don't notice this. They just invoke the presuppositional notion that a macroevolutionary change (i.e., yielding wing formation) took place through a summation of microevolutionary changes. This is their answer to the "How did it happen?" question. But it's no answer, really, because it is not at all scientific. It's just presuppositional. Unfortunately for them, it doesn't work. Their presupposition is demonstrably false.
So, we have our answer to the "Did it happen?" question. The answer is, It didn't.
(Why do I say that? It's because a half-formed wing is useful neither for flying nor running. This is devastating to the "gradual evolutionary change" theory. Natural selection will destroy the critter ever time it tries to cross species. In other words, every time it even tries to form a transition form, it will be destroyed by natural selection. This is why there are no incontrovertible transition forms in the fossil record.
To put it all in perspective, the concept of natural selection actually supports the anti-evolutionists. It explains that there are thermodynamic barriers between species.
Even S.J. Gould noticed the problem posed by the lack of transition forms in the record--which is precisely why he invoked his "hopeful monster" theory." He noticed that one can't gradually add up micro changes to get a macro change. The micro changes would have to happen all at once. [This was also his basic explanation as to why there are no transition forms in the fossil record. I have to give him credit for noticing what the creationists have been saying about that all along!] There has to be a quantum jump from one species to another. Somehow, one species has to "jump" over the thermodynamic barrier to form a new species.
Unfortunately, Gould's theory is even more patently absurd than classical theory. It is statistically preposterous. [It's like saying an alligator lays an egg which hatches a chicken.] And because it is statistically preposterous, it is thermodynamically disallowed. One does not jump over thermodynamic barriers. These barriers are by the very nature of thermodynamics infinitely high.)
Hmmm...organisms just happen to "drop" into completely different environments. Is this what happens in nature?
Maybe so, but this kind hangs out under leaves, never tree trunks.
Correlation doesn't equal causation. Besides, it's my understanding that the moth population doesn't correspond directly to the amount of local pollution or sootiness.
Nope, I don't think it's worth the time.
Is this the new creationist tactic?
When in doubt....rhyme?
Except for that 25% of the time when they are:
First, Wells argues that the story is seriously flawed because "peppered moths in the wild don't even rest on tree trunks" (:138). He repeats this point throughout the chapter. However, it is both false and irrelevant, and only serves as a distraction to lead the reader away from the actual story of the moths. Contrary to Wells's assertions, data given by Majerus (:123) indicate that the moths do indeed rest on the trunks of trees 25% of the time. The rest of the time moths rest in branches (25%) or at branch-trunk junctions (50%). The facts have been pointed out repeatedly to Wells; his response has been mostly to claim that moths don't rest on "exposed" tree trunks (). But this is not what he said in the text of Icons, which remains flatly wrong. Moths are found all over trees, which is not a surprise () and it is mentioned in the references that Wells cites.
To clear up any confusion, no researcher doubts that the peppered moth rests in trees (; ), which means that the resting substrate is bark. Entire trees are stained by pollution -- the leaves, twigs, branches, trunks, and the surrounding ground () -- and so the colors of the moths are relevant no matter where on the tree they rest -- trunks, trunk-branch junctions, branches, twigs, and even the leaves. Wells's argument implies that predatory birds can only see moths that are on exposed trunks. By making this argument, however, Wells shows an apparent ignorance of the ecology of birds and woodland ecosystems. If you walk into any forest, you can see that the birds fly from tree to tree, branch to branch, and hunt at all levels of the forest. Woodland species of birds that prey on moths and other insects live and hunt in the canopy (the leafy part of the trees). These birds are not hunting from outside, soaring above the trees like hawks, as Wells's argument would require.
In the scientific literature, there is extensive discussion of the hunting behavior of birds, including those that hunt peppered moths. Ornithologists have shown the woodland ecosystem to be vertically stratified by competition between different bird species. This zonation means that there are skilled predators patrolling all levels of the forest: the trunks, trunk-branch joints, branches, and higher canopy (; ). Further, birds learn to distinguish their prey against various backgrounds and preferentially hunt prey in locations where they have found it in the past and that birds selectively prey on the more visible moths (, ). In other words, birds hunt the prey they can see and hunt it where it is, not where it isn't. Therefore, no matter where the moth rests in the tree, it is visible to predatory birds, and thus its differential camouflage is important.
- If the first place, I want to see an absolute expansion of the Species survivability-quotient in question. If the Control Group (the Normative Species) can survive in Biomes A, B, C, and D, and the Test Group (the Mutant Variant) can survive in Biomes C, D, and E -- you may have isolated a Variant which can survive in Biome E, but you have reduced the overall survivability of the Species (from 4 Biomes to 3 Biomes).
No, you've increased the survivability. If the mutants are a new subspecies, then the species as a whole has now gone from 4 to 5 different environments. If they're a new species altogether, then you went from 1 species in 4 environments to 2 species in 5 environments. But in another sense you've actually gone from 4 to 7! You've gone from (1 species in 4 environments) to (1 species in 4 environments plus 1 new species in 3 environments). No matter how you measure it, the end result for the original population's offspring as a whole is increased biodiversity.
Same thing with the sickle-cell anemia carriers. Taken as a whole, the human species is more robust because of them.
- Secondly, if at all possible, let's see some examples other than Viruses and Bacteria. Remember, the "Fall in Eden" Model predicts that Diseases are with you always, so (alleged) adaptability on the part of Viral Plagues is not a huge surprise to the Genesis Creationist. Can we have some higher animal examples, please? If you have any to offer?
As an adult human who likes her milk, cheese, & ice cream, I really appreciate my lactose-tolerance gene - a beneficial mutation that was probably first enjoyed by my European ancestors. And though I have lost weight, I am still resolutely multicellular. :-)
Also see this T.O. article that examines the Apo-AIM mutation in humans. This mutation gives the person more-efficient HDL cholesterol particles so they scavenge arterial plaques better than the standard type, and it also helps suppress arterial inflammations. The article explains how this mutation represents an increase in information (by all the popular creationist measures).
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