Posted on 12/09/2003 7:47:21 AM PST by PatrickHenry
In what has been described as the "perfect experiment," evolutionary biologists at the University of Chicago replaced a single gene in fruit flies and discovered a mechanism by which two different "races" begin to become different species, with one group adapted to life in the tropics and the other suited to cooler climates. The tropical group was more tolerant of starvation but less tolerant of cold. The temperate group was less able to resist starvation but better adapted to cool weather.
The altered gene also changed the flies' pheromones, chemical signals that influence mating behavior. As a result, the researchers show in the Dec. 5 issue of Science, the two groups of flies are not only fit for different environments but may also be on their way to sexual isolation, a crucial divide in the emergence of a new species.
"This study directly connects genetics with evolution," said Chung-I Wu, Ph.D., professor and chairman of ecology and evolution at the University of Chicago and director of the study. For the first time, we were able to demonstrate the vast importance in an evolutionary context of a small genetic change that has already occurred in nature."
"We had the luxury," added co-author Tony Greenberg, Ph.D., a postdoctoral student in Wu's laboratory, "of watching the essential event in Darwinian evolution, the first step in the origin of a new species. We were quite impressed, that this simple alteration played such a dramatic role, both adapting flies to a new environment and changing their sex appeal. Once two groups become sexually isolated, there's no turning back."
The scientists used a new technique to knock out one gene from fruit flies and then replace it with one of two slightly different versions of the same gene.
They focused on a gene called desaturase2 that plays a role in fat metabolism. Flies from Africa and the Caribbean, where there is tremendous competition for food but cold temperatures are not a problem, have one version of ds2. Flies from cooler climates, where there is less competition for food but greater temperature variation, have a smaller, inactive version of ds2.
The same gene plays a role in the production of cuticular hydrocarbons -- waxy, aromatic compounds that coat the abdomen of female flies. A male fly, in a romantic mood, strokes the female's abdomen with his feet, which have sensors that recognize specific hydrocarbons, like a perfume.
In a previous report, Wu's laboratory found most males with the temperate version of the ds2 gene preferred females with the same gene; tropical males preferred tropical females.
"Developing increased cold tolerance was an important step for flies that migrated out of Africa to Europe and Asia," Wu said. The change in pheromones, which altered patterns of sexual attraction, "was a by-product of adaptation to colder weather."
Fruit flies have a migratory history similar to humans. They originated in Africa, spread to Europe and Asia and went on to populate the world. As with humans, there is greater diversity within African flies than between flies from Africa and other continents.
Although fruit flies have been a favorite model for the study of genetics since the early 20th century, recognition of consistent differences between tropical and temperate flies came only in 1995. The discovery, however, "has allowed a lot of analysis of the evolution of adaptive traits," Wu said.
"But this was the first time we have been able to study the process from the very beginning," he added, "to watch the first steps as one species begins to split into two, then seals the bargain by increasing sexual isolation. This is the essence of biodiversity."
Additional authors include Jennifer Moran from the Wu lab and Jerry Coyne of the University of Chicago. The National Institutes of Health and the National Science Foundation funded the study.
And you have utterly failed to give an "agenda-free" explanation for the facts I listed in 231. You don't like evolution, you don't like me and what you imagine is my agenda, and you don't like answering questions.
However, I'll answer yours. There are so many species revealed in the fossil record because there's been so much time. Actually, when life was new on earth, there weren't all that many species at any one moment. But over time, as speciation occurs, and the unfit die off, etc., you start to develop a record of life's history. And it's a very long history. Most of our close relatives (speaking in terms of earlier species) are gone now. But we're still here. So there are many fossil species of pre humans, but only one species of us. That's not so very difficult.
Now, care to take a crack at what I've been asking you?
Another apocryphal story, this one about how Galileo first got the idea for the solar system: Galileo and his wife were locked in a passionate embrace one evening. At the climactic moment she exclaimed: "Oh, Galileo ... the earth moved!"
The rest, as they say, is history.
Maybe, but if you think the earth is only 6,000 years old, I wonder what kind of engineering you practice.
re: Just look at the evidence: the apparent age of the earth, the fossil record, the observed DNA relationships among species previously thought to be related when all we had was fossil evidence, the fact that mutations occur, the fact that in every generation the unfit generally don't breed, the speciation events that have been observed in the short time we've been looking, the slowly-increasing number of transitional fossils that are being discovered (which are necessary if evolution is true, but which -- forgive my agenda-driven remark here -- are an embarrassment for creationism). )))
This is a question? At first reading, I thought it a sermon...
"Speciation events"--(g)--something like a gene pool party?
Farmers already understand breeding for type. They've done it for thousands of years in isolation from one continent to the next. They've not come up with new sheep, although it would appear to be the best laboratory for it to have happened if it can happen. It is a huge leap to go from breeding for type to new species. Chihuahuas and Great Danes .
And geneticists can't seem to do it with fruit flies, either, without tinkering with the software inside the cell.
"Transitional"(once more I observe that this term is a characterization by scientists, not a fact --by casually naming them so, you think the naming carries a persuasive weight to which I must genuflect. Despite your pouting at my heresy, I made this observation twice before; I'll make it here again. There is no proof of transitions--only a surface appeal and enormous assumptions. I'll go farther and say that it isn't even an indication--)
Farm animals are complex, but fruit flies are certainly a potential means to demonstrate what happens in nature. I observed that they have been the toys of scientists, scientists in isolation in different continents, for thousands, maybe millions, of generations of fruit flies. No new flies, yet--maybe there aren't even any in this article. A close reading of the article, when you filter out the enthusiasm (and egos), will show only the expectation, not the new species.
Seems like these favorable speciation conditions should have yielded something new with fruit flies without the Intelligent Design of the research scientist.
This is an observation--that the researchers have assumed the role of Guiding Intellect in regards to speciation-- I made which you, busy with huffing and puffing, did not address, though I made it more than once. This makes it three times.
You even anticipated this objection by listing it with others in a very early post, but do not bother to discuss it. Does anticipation of an objection carry with it an automatic dismissal? A derisive attitude only intimidates freshmen... You make all kinds of leaps and assumptions, and when called on them, proceed to insinuate that your opponents are superstitious--witch doctors or something.
You know, the "Skeptical Enquirer" may have a tiny circulation, but it doesn't mean it doesn't amuse widely. I've had copies sent to me by many evangelical athiests.
And even were a new species to happen once, could it then happen over and over again for our vast array of creatures and flora?
Oh, time, again. Om.
DNA evidence is certainly an exciting potential for the piously observant evo-geneticist. So far, they've been able to demonstrate interrelatedness and connectedness to an unaguable level. Amazing how we are genetically tied to other primates--astonishing.
There's still that *leap*, though, and the fossil record between primates is curiously scanty compared to, say, ole eohippus and Seabiscuit.
And then there's that mule problem--the bothersome barnyard cul de sac. Isolate two mules, and you'll soon have no mules, not more mules. Even under highly favorable conditions, all organisms have their mortality and fragility and fertility problems. Just try to keep animals healthy and breeding without even trying to create a new species--a whiff of bad weather, a few bacteria--goners.
Time brings death.
You have to remember that species is a human category, and is rather fuzzy. Biologists are forever arguing about it. But in general, behavioral or even geographic isolation is sufficent for speciation. An example: blue-winged and golden winged warblers, which have different but overlapping ranges. In the overlap region, one sees first and second generation hybrids, which are so different from both parents that they were given their own species names before we found out what was going on. The parent species and the hybrids are interfertile, without very much behavioral isolation. Yet we consider them two species within one superspecies.
It's very arbitrary. The northern junco, for example, has well-defined subspecies that are also quite different. Probably because the hybrids tend to vary rather continuously rather than having well-defined plumages, we consider the slate colored junco of the east, the pink-sided junco of the Black Hills, and the Oregon junco of the west all part of the same species. I live in Nebraska, and my yard is full of mutts that can't easily be fit into one of the canonical subspecies.
A large number of American duck species are interfertile. Mallards and Pintails, which are so different any experienced hunter can distinguish them at hundreds of yards, form perfectly fertile hybrids. The American Ruddy Duck has been introduced to Europe and has been hybridizing with the white tailed duck; Spanish game wardens are shooting anything that looks like a ruddy X white-tailed to try to preserve the white-tailed duck gene pool. Black ducks and mallards have fertile hybrids, and currently the black duck population is being overwhelmed by mallard genes.
The point is, if two groups are behaviorally or geographically isolated, it can keep them distinct just as easily as if they could not produce viable offspring. And it would often be almost impossible, in practice, to find out if two species that don't want to mate would give fertile offspring if they did mate. Moreover, it would make no sense to consider the mallard, pintail and wigeon the same species.
They have a recent common ancestor. Look at the DNA of a group of closely related species, and you find that the DNA sequences form what looks like a tree; that is, if you make a diagram of the minimum number of changes it takes for the sequence of one species to change to the sequence of another species, and do this for all pairs, the diagram looks like a tree. I'm not sure if anyone's done this for the chickadees/titmice.
Ontological scientists (of Big Bangs and evo-genetics) never need feel the horrible accountability of human error. They just go on to the "next best theory" without the uncomfortable knowledge that their errors led to genuine harm. They enjoy, as I said, the full scope and preciousness of their imaginations. You can trust them, put your childlike faith in them--I do not.
In teaching a course in the chemical basis of evolution this semester, I've had the opportunity to put modern molecular theories of evolution to the test. My students turned in 4 separate projects involving maximum parsimony analysis of four distinct ribosomal proteins over at least 20 species. Guess what? All four trees were in excellent agreement with the evolutionary expectations. These students are freshman chemists and biochemists, and are not in general aware of the standard phylogenies. Moreover, I urged them to look for the unexpected. One of them, for example, found a whole bunch of human pseudogenes for one of the proteins. But no refutation of evolution, not even a little one.
The point is, you can do what's nearly a double blind analysis of DNA sequences that haven't been carefully examined before, and they'll come up with results corroborating standard evolutionary models. No child-like faith is needed, just a mind that hasn't been blinded by religious fanaticism.
Whose job is it to refute evolution (defined as mutations leading to ever new species), I'd like to know? Is it the default presumption, the abiding dogma here?
Rather, it may be someone's job to prove it. This article points to the possibility of a genetic model that demonstrates how it might happen and what it might look like . But to have a guiding intellect, in the form of microsurgical tampering with the DNA inside the cell of a fruit fly...it's just absurd to say that proves that evolution provides our origin...although it does add some fuel to the ID case. Amusing.
I've known few professors whose pet theories and vanities (and hopes of a plump new grant) were challenged to have much of a sense of humor about much of anything.
They start huffing and puffing and claiming a challenger "doesn't like me or Carl Sagan"... no fanatics, here!
As for chickadees, that was a throwaway I offered, . Sellers of evolutionism ideas ( and scientists are ultimately salesmen) might indeed stick to birds. They offer nice short generations, lots of offspring, and their own form of transportation (to achieve that important geo isolation) make them a likelier candidate to prove the theory. Maybe one day a leap can occur between an undeniable similarity and relatedness (which undeniably proves-- similarity and relatedness!), to a new reliably documented species.
You know, it might help your temper to take some time off from science and explore a sister subject, logic, in the philosophy department. There is so much silly about this reply I don't know where to start. I promise, I say this with no dislike whatsoever. I wouldn't have devoted so much digital ink if I were motivated by dislike.
But--a leaf exists, and so does a planet. They are both amazing things. My assertion: We are not capable enough of understanding either well enough to create either. Not exactly an outlandish statement.
But we think we understand them well enough to claim we know how they started. And, my, do those claims sound dogmatic !
No, nylon is not a petroleum distillate; it's a specific polymer. The bug in question attacks the junction between units of the polymer: Hence its name, "6-aminohexanoic-acid-oligomer hydrolase". It has nothing in common with the straight- and branched- chain hydrocarbons found in petroleum.
So, unless you have more data about this, (like for example, evidence that it exists elsewhere), your suggestion appears to be without merit.
If you had read the link I provided, you would realize that this particular enzyme is coded for by a gene that differs by exactly one base pair from a gene that codes for an enzyme necessary for carbohydrate metabolism. Sure sounds like a simple mutation.
BTW, it didn't "somehow evolved because nylon was made". It is quite likely that this particular mutation has occurred many, many times in the past, and was fatal (what's to prevent it? Even if prekaryotes had the elaborate gene-repair mechanism that eukaryotes do, no such mechanism is 100% perfect). It only managed to be nonfatal when, fortuitously, it found itself in a medium with nylon.
I don't know how old the earth is. But let's says it's 1 billion years old. Is that old enough for evolution to be responsible for all the world's species?
I'm looking for data about estimated rates of speciation. I found your previous links on biological species concept very informative, thought you might have more...
I'm trying to figure out if you're an inquisitive youngster, with a budding interest in geology and biology, or whether you're an adult who has spent a lifetime avoiding such information, and perhaps sneering at those who have made the effort to learn.
In either case, I suggest starting with something basic and introductory. For example: A Short History of Planet Earth for geology; and What Evolution Is for biology.
This article's title is simple a lie--within the article are only assumptions of possible new speciation.
Where's out new science-created fruit fly? bump
Found a nice long article about a scientist named Suzuki, too--he did similar attempts at new flies decades ago, without the microscopic gene-splicing, of course. You may be interested, but... No new flies.
You posted the original article--I suppose you expect Wu to stand behind the title? It could be possible that he did not write the headline, perhaps a journalist got too enthusiastic, but it comes from the U of Chicago hospital and I've found no qualifying since. They really should not have claimed such a breakthrough, or allowed this title to stand unqualified, on hopeful expectation alone.
But it is SO hard to get a good grant these days! Sometimes the temptation to embellish is well-nigh irresistable.
I'll check back in three more months to see if 90 more generations have produced the promised NEW speciation.
Any news yet? New flies on the fly? I googled, and only found the Old News--where Wu promised, but we don't yet get to see....
How dependable are the words and promises of scientists....? Will he deliver?
bump
Fruit flies have been used to instruct and study genetics since genetics first began as a science--three hundred years and more of taking advantage of the fruit fly's swift passage of generations (24 hours). These experiments are often in great geographical isolation, over centuries and different continents.
Yet, amazingly, there are as yet no new species of fruit fly to emerge from this ideal environment for speciation.
This thread is an object lesson in the hopelessness of laboratory reproduction of the notion of evolution. Not only was the claim of the original article bogus on its face, but nine months more have not produced the "new species".
Even delving into the DNA of the fruit fly, a highly artificial endeavor available only with the newest microsurgery techniques, have as yet failed to produce new species.
But hope and faith springs eternal.
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