Posted on 02/24/2006 4:12:32 AM PST by PatrickHenry
Charles Darwin would undoubtedly be both pleased and chagrined.
The famous scientist would be pleased because a study published online this week provides the first clear evidence that natural selection, his favored mechanism of evolution, drives the process of species formation in a wide variety of plants and animals. But he would be chagrined because it has taken nearly 150 years to do so.
What Darwin did in his revolutionary treatise, “On the Origin of Species,” was to explain how much of the extraordinary variety of biological traits possessed by plants and animals arises from a single process, natural selection. Since then a large number of studies and observations have supported and extended his original work. However, linking natural selection to the origin of the 30 to 100 million different species estimated to inhabit the earth, has proven considerably more elusive.
In the last 20 years, studies of a number of specific species have demonstrated that natural selection can cause sub-populations to adapt to new environments in ways that reduce their ability to interbreed, an essential first step in the formation of a new species. However, biologists have not known whether these cases represent special exceptions or illustrate a general rule.
The new study – published online in the Proceedings of the National Academy of Sciences – provides empirical support for the proposition that natural selection is a general force behind the formation of new species by analyzing the relationship between natural selection and the ability to interbreed in hundreds of different organisms – ranging from plants through insects, fish, frogs and birds – and finding that the overall link between them is positive.
“This helps fill a big gap that has existed in evolutionary studies,” says Daniel Funk, assistant professor of biological sciences at Vanderbilt University. He authored the study with Patrik Nosil from Simon Fraser University in British Columbia and William J. Etges from the University of Arkansas. “We have known for some time that when species invade a new environment or ecological niche, a common result is the formation of a great diversity of new species. However, we haven’t really understood how or whether the process of adaptation generally drives this pattern of species diversification.”
The specific question that Funk and his colleagues set out to answer is whether there is a positive link between the degree of adaptation to different environments by closely related groups and the extent to which they can interbreed, what biologists call reproductive isolation.
Funk and his colleagues saw a way to address this question by extending a method pioneered by two scientists in a now classic study of species formation in fruit flies published in 1989. The original method measured the way in which reproductive isolation varies with time. It proved to be very powerful and a number of other researchers applied it to additional species. Funk and his colleagues realized that if they used the results of these studies and added an ecological dimension then they would have an approach capable of measuring the link between natural selection and reproductive isolation.
“We thought that the idea itself was important, that this is a really powerful approach to a very major question,” says Funk, “but we thought that there was no way in the world that we were actually going to get statistically significant results.”
The reason for his doubt was the incompleteness and lack of uniformity of ecological data. “There are all these species out there and so few of them are known in intimate detail, so any kind of ecological characterization, through no fault of ecologists, will be limited in accuracy and precision,” Funk says.
Nevertheless, the researchers decided to do the best they could with the information available. So they collected information from the published literature on three basic ecological variables: habitat, diet and size. Then they used this information to calculate the differences in ecological adaptation between the hundreds of pairs of related species in the original studies.
When they compared these differences in adaptation with the degree of reproductive isolation for each pair and then added them up, the researchers found that the overall association was positive with a surprisingly high level of confidence: The odds that the association is simply due to chance are only one in 250, substantially higher than the standard confidence level of one chance in 20 that scientists demand.
“The fact that the association is statistically significant despite the crudeness of our estimates suggests that the true biological association is very strong,” Funk says. “Darwin’s famous book was called ‘On the Origin of Species,’ but it was really about natural selection on traits rather than species formation. Since our study suggests that natural selection is a general cause of species formation, it seems that Darwin chose an appropriate title after all.”
[Omitted contact info which is at the end of the article.]
Thanks! interesting theory, even if a little 'far out' with the interstellar ships.
"...all at once ..."
This is the "fizzle" as compared to an "explosion".
There are those who believe, as did Velikovsky, that things as complex as houseflies can simply pop into existence given the right conditions. The same term applies.
Must be careful with this term since it's not necessarily linked to evolution in many of its manifestations.
Since you have great library facilities available, get this book "Invertebrate Paleontology and Evolution" by E.N.K. Clarkson, 4th edition. It is highly readable. It will help you understand about those sponges (BTW, many still have Si spicules).
You're an interesting guy. You must live near a University if you have serious libraries nearby. Walking has all kinds of health benefits.
What is the significance of your name, muawiyah? Is it an American Indian name?
That's why it is "Directed Panspermia". The ships could protect the bugs on their way, which would be a very long distance and a very long time. Bugs or viruses floating in space (undirected) wouldn't last long.
No, it's an Arabic name I happened to pick up in college years ago. I've found it to be a very useful pen name.
This is in the Washington DC suburbs. We have Library of Congress available 20 minutes away, but the university libraries here are OK, as are the public libraries.
We probably have that one around here somewhere. Last year I moved out several thousand books that we no longer needed because they were out of date or were on-line.
It's why we use "Abiogenesis" - life arising from non-life. Whether it's a pop! or many baby steps (more likely) is the same. It is only related to evolution in that successful Abiogenesis gives something for evolution to operate on. The Pasteur/Spontaneous Generation aspect is unrelated to either Abiogenesis or Evolution.
Let me say right here I didn't think so until a couple of years ago a guy ran an electric current through a strand of DNA.
Also read Penrose's Emperors New Clothes too.
A good case can be made that we are just machines ~
My original question still stands.
How did the "bacteial slime" get here?
When will they make a spell checker that will correct my mistakes, whatever kind they are.
The point I was making, though, is that simply because we have life on Earth is no reason to rule out life elsewhere.
Here's a thought experiment for you. Let's say there's a gazillion genes out there in the ocean already "designed/capable" for/of various purposes ~ that is, they are "parts" and they're ready to go.
If those new "parts" get installed in the genome of a cell (let's call it a "critter"), does that result in an evolutionary change, or rather something more like putting a supercharger in a '57 Chevy (and not the one up on blocks we discussed in another thread earlier)?
Remember, that supercharger has to fit, and that may take an additional mounting bracket to match up the Chevy head with the new device, and it's guranteed to improve performance (if not MPG).
Evolution, by definition, does not necessarily result in an improvement in performance, just adequacy given conditions. We certainly cannot say that Chevy evolved! At the same time there appears to be a general trend in critters over the last couple of hundred million years to be smarter and to work more efficiently in adverse conditions. For example, Polar Bears are rather quick witted and certainly live under nasty conditions, yet, voila, they have hair that's "hollow" and conducts light to their skin! One really does have to ask how it was Polar Bears happened to pick up that gene! Other critters have it as well. These guys don't necessarily share a recent common ancestor either.
So, are we looking at evolution or new parts from a vast storehouse of "new parts".
We must imagine that this is the case everywhere else in the Universe.
Used to be ~ last year I suppose ~ most biologists believe that viruses were created after the bacteria ~ not that they arrived after them.
Now, there's an idea afoot that bacteria arose out of an RNA world, or from viruses.
Recently there was an astronomy report that there was a vast region of space discovered that had complex chemicals in it typical of bacterial cells. Didn't mean cells had actually been found, but the stuff to make them had been found in space.
"Used to be ~ last year I suppose ~ most biologists believe that viruses were created after the bacteria ~ not that they arrived after them.
Now, there's an idea afoot that bacteria arose out of an RNA world, or from viruses."
This has long been a friendly controversy among microbiologists. It appears some viruses are degenerate, but the work with self-replicating RNA shows that it could have been before cells. 10-20 years from now, we'll have a much better picture and I predict that both will be right.
I would like a reference to the "vast" areas of space with chemicals "typical of bacterial cells", please.
BTW, not looking it up at this late time of day, but there was a recent discussion of a "scientific nature" about the possibilities of a crysalized insect egg actually making it all the way across the galaxy in a meteor.
I gather the purpose of the discussion was to pursue the limits.
Will try to remember it.
Might try the NASA site on the net.
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