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.
Name one successful random mutation that resulted in a new species that you can prove from accepted scientific observation practices. No, extinct animal A that is similar to living animal B proves nothing because no change was observed.My response (in 211) was this:
"If you were provided with information showing exactly this [observed speciation], would it change your mind in the slightest?"In other words, I asked you if I'd be wasting my time to deal with you as if you seriously cared about the evidence. Are you an intellectually curious person who wants to learn, or are you evidence-proof? Here's your answer:
You are so dedicated to evolution that you cannot even see how ridiculous it is to claim that because it has been done in a lab it could happen naturally. It is the same as declaring that because computers exist, one HAS been accidentially formed in a volcano.
Clumsy little tapdance. You have (rather awkwardly) sidestepped the challenge that you yourself have posted. Of course, in view of the information that I already provided (see the links in post 216) I don't blame you for feeling a bit trapped. But the appropriate response would have been: "Oh. Thanks for the information." But as I've often remarked: Creationism is never having to say you're sorry.
Seems to me a more compelling speciation event would be more than showing the reproductive mechanism is broken. How about some physical change beyond genetic variation?
In other words, how about something observed that satisfies the "folk" definition of species (tell them apart by looking at them) or "phenetic" definition (by ordinary means)?
I agree that the experiments show that these creatures adapt to their environment, over generations, including not even producing offspring that will be de-selected from the environment.
In other words, they genetically tend towards traits that will survive in the environment to the point they genetically don't bother to even produce offspring that are not adapted, should they have an opportunity to mate with the other population.
How is the evidence of more than broad variation inside the same phenetic species?
Doesn't it still take a leap of faith to believe these events show a fruit fly population off on its way to becoming bumblebees?
Anyway, how many such changes should we be observing to account for all the species of all the creatures in the world? In other words, is the world old enough to support these theories?
(Enough of this dry scientific stuff -- I'm off to DU to see how they are handling the news of Saddam's capture!)
At least you pose some qualifiers in your discourse. And, at one level, selective breeding cannot be argued against. Look at how we managed, over thousands of generations on several continents, to create breeds (most of our present domesticated sheep) of sheep who cannot shed their wool, so that their wool might grow very long. These sheep will eventually die if left unshorn long enough. And the merino sheep was bred to have lots of skin (think of a bloodhound's face with his wrinkles) so that the surface would support even more follicles of valuable wool. At the same time, other breeds of sheep became valued for their twinning propensity and their heavy body shapes--mutton sheep. Twinning among sheep used to be rare--now it is very common. The shepherd has to really work with the ewe to get her to accept both lambs, though, but this is also ancient lore.
The breeds of sheep are fascinating, because they are very ancient. I'd think they'd have managed with fruit flies long before this, given the fervor of evolution-origin priesthood , since the fly's brief generation is the blessed toy of geneticist experimentors. It has been for almost two centuries. Given the 24-hour generation of fruit flies, that's lots of generations. A good bit of time, and a good bit of space, lots of right conditions.
But, as you said and has been often said, there is never time enough.
When I visit museums of natural history, and all the eons of dead species are presented before me, it's a lonely feeling. There's so few of us species left, compared to what was.
Yes. Exactly. "We few, we happy few."
To me, looking at things from an evolutionary point of view, human life is far more valuable if it's the result of evolution than if it isn't. If the gods can end our existence whenever they like, and then with a snap of their divine fingers start it up all over again, and if they can repeat such whimsical actions as often as they wish, then we're little more than cheap toys, to be discarded without a thought, then re-acquired again at no expense. What's so special about human life in a setup like that?
Evolution teaches that we find ourselves at what is presently the end of a long line -- a very long line -- of fortuitous mutations that have survived innumerable extinction events and natural calamities. This implies that our kind will never happen again. I think that makes us very special, very rare, very precious. That's the perspective I gain from understanding evolution.
Not a leap of faith. A rational inference. There's a big difference, because a leap of faith is done in the absense of evidence.
Anyway, how many such changes should we be observing to account for all the species of all the creatures in the world? In other words, is the world old enough to support these theories?
I assume that demonstrating some observed instances of speciation isn't sufficient for your exacting requirements. Why not? In a short span of years, we can see that speciation does indeed happen. This is something that the creationists have been claiming never happens naturally. Now it's seen to happen naturally.
So what do the creationists do? Do they admit they were wrong? Of course not. They move the goalposts and say "Not enough evidence!"
So, with your exacting demands for ever more evidence, tell me ... what's your evidence for creationism?
From a science point of few, specialness is irrelvant. You are certainly getting close to another of my pet themes--the hubris of scientists. The more unaccountable (as Rightwingprofessor alludes with his "it's unexplorable, therefore don't expect to know anything but what I tell you to know" ) the field of study, whether BigBang in astronomy, or formulating competing fairy tales as to the origins of human life--the more hubris. The more "scope for the imagination" as Anne of Green Gables said.
The evidence should lead to a reasonable conclusion, but you are reasoning from the other direction with an agenda of your own--that agenda being the ascendence of the scientist. Perhaps even a sort of science priesthood.
It's so easy to avoid those pesky qualifiers (or hide them under heaps of exhuberant self-congratulation) when no one may gainsay you, one way or the other. What cannot be disproven also may not be proven.
I find the claims of the UofChicago, as presented in this article, to be outlandish in the extreme.
If I might share, and this not be too much of a Sunday School bore...
Was discussing with my youngest why there is a God, and why I know this. This is not a discussion of evolution, exactly, though it does involve nature.
I pulled down a leaf and explained how this leaf was a factory, turning sunshine into fuel (sugar and cellulose), taking water and minerals from the soil and converting them into something entirely new. I explained that human beings can build factories, but cannot make them live and breathe. With all the brilliance of the scientists, they cannot create a single leaf . Artists may render the image of a leaf, botantists study and understand them (mostly). But we can't make one. Not a single one.
Perhaps we can penetrate the DNA and change what has already programmed the software of that tree, and call ourselves "special" and beyond the reach of that capricious (?) divinity.
We still can't make a single leaf. Yet it is.
From your first link, it apparently depends on what the definition of speciation is:
What a biologist will consider as a speciation event is, in part, dependent on which species definition that biologist accepts
All I am saying, is that a more compelling speciation observation would satisfy the "folk" or "phenetic" species concept -- ie something physically changed -- rather than the "biological species concept" (BSC). Seems to me that in a few thousand years of human history, some creature would have been observed evolving new traits. Something beyond the reproductive ability being broken.
Otherwise, if evolution is moving that slowly, is the world really old enough to have evolved all these species without an intelligent hand?
So, with your exacting demands for ever more evidence, tell me ... what's your evidence for creationism?
See my last question above.
Fine. Please strip away whatever agenda you imagine I bring to the table. Assume that scientists are every bit as ignorant and irrational as witch-doctors in the rain forest.
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).
Those are the observed facts. Please avoid all ideological agendae. Now give us your "reasonable" interpretation of the data.
We can't make a planet either. Is astronomy bunk?
Yes, evolution moves slowly, too slowly to satisfy your "folk definition" of speciation (what would that be -- a goldfish giving birth to a cow?); and yes, the earth is old enough to accomodate the theory of evolution. How old do you think the earth is? I gather from your previous post that you think your "evidence" for creationism lies in the fact that there hasn't been sufficient time for the evolution of life on earth. What makes you think that there hasn't been sufficient time?
The scientists I have known, and know, are driven by the same things that drive everyone. Ambition. No one wants to die in oblivion. There is this need to set one's self apart, to distinguish the self. With academic scientists this manifests in variations on publications and other media "face time". There is also the survival hunter-gatherer instinct--writing and qualifying for grants.
I've been around long enough to remember Carl Sagan and his TV appearances. I enjoyed them, but couldn't take him very seriously. Indeed, a lot he promulgated has been dismissed. Billions and billions. Sounds a whole lot like a geneticist/evolutionary when pressed to explain how these "leaps" take place when you and I have never witnessed the emergence of a new, multi-celled species, nor had a reliable account of it in the past!
Frustrated with the time problem in driving out the annoyingly superstitious, the scientists in this article have said, "Let's take matters into our own hands and shut 'em up once and for all." First of all, they have not yet succeeded in what your thread title claims. They believe they will probably "create" a new species, but have not as yet. Even if they do, intellect-driven microsurgical tamperings do not occur in nature.
Have you stop to consider that these scientists may well have demonstrated that new species emerge only when the DNA is directly tampered with, via an ambitious intellect? Wouldn't that be a kick in the ole head, though?
As far as transitional species go, a sheep is an awful lot like a goat. (Forgive my constant references to sheep. I have an interest in textiles and fibers.) Both have been domesticated for thousands of years in isolated places. As yet, we have no new sheep or goats nor even a sterile goat-mule (that I know of. I recently found out that donkeys can sometimes be crossed with zebras to make a mule). Similarities between species bring a surface appeal to your argument--but there's still that huge leap I referred to.
And more than insinuations of superstition to evo-skeptics will bridge that gap.
Why are there so many more species in the past than are in our present? The mosaic was once so much more brilliant. You call them "transitional", but what a huge assumption is in your casual naming! No mammals are seen in certain fossil records, so perhaps it is not unreasonable to assume they did not exist with that record. It is not reasonable, however, to insist that such is absolute proof. Only an indication.
One branch of science I follow, as best I can understand, is pharmaceudicals, for investment purposes. When you read the literature the scientists put out for medications, it is heavy and ponderous with modifiers and qualifiers. That's because their science is absolutely accountable. If they are wrong about what they claim, they'll kill people ... but literature about the origins of humans and other complex mammals is so frothy.
No bothersome "maybes" and "indications are". Just--"We now have stamped out superstition forever."
Those [listed in 231] are the observed facts. Please avoid all ideological agendae. Now give us your "reasonable" interpretation of the data.What you've done is give me more "agenda" stuff (scientists are driven by ambition, they want grant money, etc.). You don't like Carl Sagan, although you've cited no errors on his part. You don't like the term "transitional species," although you don't offer any other explanation for what they are. You don't like the scientists in the pharmaceutical industry. Fine. We're developing a splendid collection of things on your personal "I don't like" list. Which doesn't help us resolve the issues here.
Now then, back to the unanswered question: What are your (presumably) agenda-free conclusions about the facts I mentioned in post 231?
I happen to like the scientists in the pharm industry because they are sufficiently humble. They are humble because they know they can kill people and other people will know full well that that is exactly what has happened, when it happens. I believe I said as much--they know better than to leave their claims unqualified by possible disaster.
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.
You affect an indignation I do not think you feel--a defensive mechanism, and a posturing gesture of injury not made. I addressed fully your questions.
You, however, did not respond to a question I asked twice.
Why were there so many species eons ago---and so few species today?
How fast does speciation occur? How many speciation events or other mutations were required to go from "primordial goo" to human? How old is the earth?
Thats all I'm asking. Basically, does anyone have numbers to estimate how long it should take to evolve a human. Just seems to me that it's a very long time, since we don't see much evolvin' going on.
But then I'm an engineer and I like dealing with numbers.
Stellar structure and the carbon cycle was understood long before the hydrogen bomb was invented (or discovered as the Platonists assert.)
Likely Apocryphal Story: Hans Bethe was strolling with his wife one evening when she said "Don't the stars look beautiful tonight?"
Hans supposedly responded "Yes, and I am the only person in the world who knows how they do it."
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