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.]
Anyone who gets involved in these threads who is unfamiliar with panspermia probably shouldn't get involved in these threads.
For the most part we really don't know enough about biology yet to pin down the processes that brought it into existence. I'd give it half a billion years or so before we have the confidence to speak with absolute certainty on the matter.
Keep talking.
None of this stuff has to have any control at all ~ it just "is".
Everybody beleives that some things just are.
I was curious what muaw had to say to. Maybe reading up on it? ;)
http://en.wikipedia.org/wiki/Panspermia
http://www.daviddarling.info/encyclopedia/D/dirpans.html
I have a question for you. How is Panspermia related to Exogenesis?
The chances of "undirected" panspermia seem to be very minute, if any.
I like you idea (if I'm stating it appropriately) that panspermia caused the "Cambrian Explosion". I just don't think you have completely thought out what a fizzle that really was.
Philip Jose Farmer had a better handle on it than Delaney or Tolkien.
So, if there's something meaningful in the Hobbitt, you'd best C&P it 'cause otherwise I'll never see it through all that glaze.
Hmmmmmmmmm. Well, the dwarves sent old Bilbo up a tree to see how far they were from the end of the trail. But Bilbo was too thick to realize that they were near the end of the trail. All he saw was trees.
Neither suggest any motive or direction for any of it.
You realize that the concept was well discussed in science fiction of the 1920s and 1930s.
I saw your suggestion regarding Wikipedia. Frankly, I rarely use that site preferring instead the popular science press - Scientific American, Discover, and Science News. If a piece looks interesting and readable, I'll go to the library to read the journal.
I haven't read much science fiction, so you are more of an expert than me.
That's very ambitious to go to the library to read the journals. Very admirable to go right to the source. Are any of the journals online?
At the time they'd not been able to research what went on at the microscopic level. More recently some of the researchers report that the hard stuff began much earlier. Doesn't make it a "fizzle", just that it happened at a different scale, and much earlier. I've not been terribly impressed with the macro-critters ever since I read a piece where the guy took some of the wierdest stuff and flipped it over showing that it was quite recognizable. BTW, I have an interesting selection of shells from the New Cut on the Ohio (at Madison) as well as fossil sponges made out of silicon. Always wondered what happened to those sponges.
A long term, continual stream of viral bodies could have provided the genetic input necessary to turn all that bacterial slime into critters.
That is, in fact, the human condition.
This stuff changes though.
I have several serious libraries nearby so it's easier to just go to the library, besides, I have to walk a couple of hours every day for purposes of health.
The "third" proposal is that life is just a consequence of all the natural laws we already know about, so it happens everywhere ~ I know it has a name but it escapes me at the moment.
Is that any different than Abiogenesis and Evolution?
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