Darwin's Theory, What Scientific Evidence Best Supports Evolution By Natural Selection?
What scientific evidence best supports evolution by natural selection?
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Here's an interesting article:
New evidence that natural selection is a general driving force behind the origin of species
Co-authors Patrik Nosil, front, and Daniel Funk
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.
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.”
Source: Vanderbilt University
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.”
Source: Vanderbilt University
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If you mean getting a different looking animal from the cross breading of the 2 animals i would say the human being and dogs and maybe horses..there are many others but these would show the biggest difference over a short span of time...but i would not call it evolution as thought of by the scientists of today more like breeding for the desired effects or traits...which is not a hundred percent all the time..
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Well, the most obvious is the fossil records which show changes through species. If you just talk about humans, fossil records of earlier human/ape hominids show characteristics like skull, jaw, spine, dental and other bodily structure changing through the species,. I.e very early hominids have small, ape like skulls whereas going up through the other species of hominids they gradually and visibly increase in size so later hominids have larger skulls that barely resemble modern ape skulls and look more like human skulls. You can also look at traits of other animals which follow the exact same trend.
You can also use DNA and other chemical similarities between species to prove evolution. Everyone knows that apes share like 98% of the same DNA as us, but its not just apes, even animals that bare almost no resemblance to us share a huge amount of the same DNA. Humans have genes for even reptilian features, although they just aren't active, so they don't show.
You can also look at facts like all life on earth has the ability to create complex molecules from only carbon and a few other elements. In fact 99% of all proteins, carbohydrates, fats and other nutritional molecules made by ALL life on earth are made of only 6 of the 92 common elements. All life from single cell bacteria right up to mammals start off life as a single cell and divide and grow by almost identical mechanisms.
There is loads of other evidence for evolution, those were just one or two of the basic general evidence. If you want more here's some from wikipedia: en.wikipedia.org
You can also use DNA and other chemical similarities between species to prove evolution. Everyone knows that apes share like 98% of the same DNA as us, but its not just apes, even animals that bare almost no resemblance to us share a huge amount of the same DNA. Humans have genes for even reptilian features, although they just aren't active, so they don't show.
You can also look at facts like all life on earth has the ability to create complex molecules from only carbon and a few other elements. In fact 99% of all proteins, carbohydrates, fats and other nutritional molecules made by ALL life on earth are made of only 6 of the 92 common elements. All life from single cell bacteria right up to mammals start off life as a single cell and divide and grow by almost identical mechanisms.
There is loads of other evidence for evolution, those were just one or two of the basic general evidence. If you want more here's some from wikipedia: en.wikipedia.org
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