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.]
It doesn't matter if, say, a shoe salesman or an Oom Paul Kruger believes the world is flat or doesn't believe in evolution.
In our free society he can even argue with a scientist. It is a waste of time if the scientist argues back.
"The new study – published online in the Proceedings of the National Academy of Sciences",
The 1989 study should be in the reference section of the original article, but who can access it online.
Latin hyper-cubes?
Yes I do know that they are cross species reproduction and I also know that the mules and jennies are sterile. They therefore have no bearing on the discussion.
As for the dog breeding you suggest I have heard of successes of such pairing. (With the male being the smaller dog)
It is estimated that man was on the American contents 10,000 years (I read an article recently that upped that to 16,000 years) before the Europeans arrived with a conservative generation of 20 years that is 500 generations. That is not huge on the evolutionary time table but not insignificant. Name a significant trait that natural selection produced in humans on the North or South American Continent.
I'll be one volunteer to be a FReepSpeak spokesperson. I'll keep those idiots in line. ;)
(What is FReepSpeak btw?) LOL!
It is not a successful breeding because the offspring is sterile.
We aren't allowed to use a certain three-letter word that starts with "L".
The Chihuahua will become 'dog food'.
How many 3-letter words start with 'L'? Lie?
Creationists don't l-word. They may, every now and then, post a "frequently-repeated error," sometimes called (after the poster has received numerous corrections) a "compulsively repeated error." But they never l-word.
Those ~10,000 years of separation produced the differences between indigenous Americans and Asians that we see. 10,000 years is a lot less significant than you appear to think, on an evolutionary time scale. It took six million or so years to produce the differences we see between humans and chimpanzees - that's 600 times as long as the time scale you mention (at least 300,000 generations, probably more).
Speciation is such a slow process that we don't expect to observe blatant examples of it happening in observable time spans (such an observation would be evidence against our understanding of evolution). What we do expect to see are species in the process of evolution, which are observed all the time. Geographically extant ring species are prime examples of a 'freeze frame' of evolution in action. They're one species (sort of), that could easily become two species if a minor extinction event took place somewhere in the ring.
I just want to be clear. You are saying that natural selection is not predictive, right?
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).
Oh, yeah? Well then please explain why else the chihuahua would have asked the bull mastiff: "Did I hurt you honey?"
Very small body size in the Amazon; barrel chest and high lung capacity in the high Andes; cold adaptation, including slight relocation of forearm veins and arteries, in Tierra del Fuego.
The evos, though, fail to comprehend how much information is packed into DNA arrays, while at the same time underestimating the true degree of technical difficulty life represents, and they underestimate the time needed for what they call "evolution" to work.
I'm taking the position that life didn't just spring up on Earth and start evolving. Rather, it had already been long developed, but "drifted in" to Earth. Further, we simply do not yet have the slightest glimmering of how incredibly complex life really is.
They help keep you alive and thriving when all you have to eat is meat or fish, the night is 24 hours long (requiring you to see in the dark), and it's really cold!
Up until the Middle Ages the Polar Peoples were physically isolated from all but the most intrepid outsiders.
I assume you mean hinnies? It is generally true that mules are sterile but it is not universally true. According to this
Since 1527 there have been more than 60 documented cases of foals born to female mules around the world.
Whatever they are called, even one instance of fertile offspring proves that horses and donkeys are NOT different species (unless, of course, you believe in the sort of speciation that gives you nearly 7 million different species of salmon, to say nothing of tuna).
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