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.]
Slippery slope! So you're versed in Systems Thinking! Cool! Peter Senge or Russ Ackoff?
cheeseburgars = cheeseburglars
Do you have any eamples of CRIDers attempting to prove anything? Thanks.
Funk and his colleagues saw a way to address this question by extending a method pioneered by Jerry A. Coyne, University of Chicago, and H. Allen Orr, University of Rochester in a now classic study of speciation in fruit flies published in 1989.This isn't the same as the abstract I linked earlier.Coyne and Orr were interested in exploring how the process of species formation develops over time. To measure this process, known as speciation, they developed an index of reproductive isolation. For a measure of time, they used the fact that genetic mutations accumulate over time. So if the percent difference in the genomes of species A and B differs by five percent while the difference between A and C differs by 10 percent, then the time since A and C diverged is about twice that since A and B split apart.
Extending the methodology of a classic, 1989 study
Coyne and Orr's approach provided a number of valuable insights into the speciation process, such as showing that a certain amount of time must pass before reproductive isolation evolves and that it isn't a sudden but a gradual process. Other researchers were impressed with the power of their method and applied it to a number of other groups of creatures. In Coyne and Orr's book, Speciation, published in 2004, the scientists listed eight different studies that applied their approach to flowering plants, birds in general, doves in particular, fruit flies, butterflies, frogs, fish in general, and a specific type of fish called darters. Together, the studies evaluated many hundreds of species.
"I got the idea that we could extend the analysis into a third dimension, ecological divergence," says Funk. He realized that applying this new approach to data from each of the eight studies would have two major advantages:
Freedom from bias. The studies that had been previously subjected to the Coyne and Orr analysis provided the researchers with an unbiased sample. Many of the individual case studies that have found a role for natural selection were picked for study because the investigators detected indications that this was the case and so, as a group, the cases suffer from a pro-natural-selection bias.
Eliminating the time factor. The results of previous speciation studies have been clouded by the effects of time. Regardless of the role that natural selection plays, random mutations are bound to increase the reproductive isolation between two groups over time. In earlier studies, it has been difficult -- if not impossible -- to disentangle the two effects. With the proposed approach, however, the authors could apply a widely used mathematical procedure, called regression analysis, to factor out time's effects and isolate the impact of natural selection.
Something known to biologists for centuries, and discussed extensively by Darwin.
I do not see how any odds are "against" evolution. Perhaps you could elaborate.
Some 5000 years ago!
Heretic! He did it at 9:00 AM Greenwich time, April 24, 4004 BC! That's 6002 years ago! (Give or take a month.)
...in the seventeenth century [1644], in his great work, Dr. John Lightfoot, Vice-Chancellor of the University of Cambridge, and one of the most eminent Hebrew scholars of his time, declared, as the result of his most profound and exhaustive study of the Scriptures, that "heaven and earth, centre and circumference, were created all together, in the same instant, and clouds full of water," and that "this work took place and man was created by the Trinity on October 23, 4004 B.C., at nine o'clock in the morning."
Andrew D. White, A History of the Warfare of Science with Theology in Christendom (D. Appleton and Co., 1897, p. 9).
http://www.lhup.edu/~dsimanek/ussher.htm
>>>
*My* version of the Bible says April 24th! Burn heretic burn!
April 24, October 23, what's the difference. Both days are on daylight savings time.
There's always Jack Chick....
"Manifold mendacities".....
Haha. Just fyi, the idea that viruses might account for some lateral genetic transfer had occured to me long ago. How much is unclear. What is clear is 1) viruses don't account for many of the forms variation we see (e.g. SNPs, chromosome doublings, halvings, crossover, merging) and 2) variation, of whatever nature, is, by itself, not an explanation of speciation.
It's almost as if birds and tree dwelling mammals had the same genes,
But *do* they have the same genes that express this property?
In fact, we (meaning everybody but the bacteria) have chromosomes shaped just like those found in viruses.
This is not true. Chromosomes are double-stranded DNA macro-molecules. Many virus genomes are composed of RNA. Others of single-stranded DNA. Some have double-stranded DNA. Furthermore they are generally much shorter than what we'd consider a macro-molecules.
No they aren't. I don't want to get tied up in minutia, but, while I agree that you characterized natural selection as post facto, the cheeseburger example wasn't. I took you to mean that, based on past experience, one can generalize a "Theory of McDonald's," from which one can predict that a never-before-visited McDonald's will serve cheeseburgers. That is not post facto.
Let's get back to it. Please anwer clearly. Do you think that natural selection is predictive or not?
"In fact, we (meaning everybody but the bacteria) have chromosomes shaped just like those found in viruses."
Would elaborate on this with some real references or links please?
No, no no. "Ever" is only 4000 years.
Did you read that passage carefully? Or were you in too much of a hurry to sling gratitous insults?
should-i-bother-reading-this-thread PLACEMARKER.
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