The evolution of life is a fact. No one doubts the fact that life has evolved through time. There are many theories of how life evolved. Darwin's theory of evolution is the most widely accepted theory. There is no such thing as a single "Theory of Evolution".
George McGhee, Jr is the first person, who I have seen, to get it right. Other people have stated that Evolution is both a theory and a fact, which is incorrect.
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In his book The Late Devonian Mass Extinction, George R. McGhee, Jr. writes (bolding and coloring added by me):
EVOLUTION IS a fact. It is an empirical observation, not a theory. Life has evolved in the past and is still evolving today. Visit the laboratory of any population geneticist or ecologist today and you will be shown evolutionary change in the organisms they studied in the modern world. Visit the laboratories or field sites of paleontologists and you will be shown the actual record of the evolution of life in the past.
Imagine a bright red key on the keyboard of a supermegacomputer that, if pressed, would erase the phrase "theory of evolution" from the literature everywhere. I would be the first to press that key. That phrase has caused enormous confusion, especially for the general
public. I would replace it with phrases like "theories of why evolution takes place" or "theories of how evolution works" instead, with emphasis on the plural, as that is what is really meant. In fact, the great majority of times you encounter the phrase "the theory of evolution" in the popular literature what is actually meant is "the theory of natural selection."
page 247
What is evolution? In Charles Darwin's time, a general definition would have been "descent with modification." And that is not a bad definition. It means that one generation of animals or plants produces the next generation of offspring, which in turn produces the next generation, and so on. This is the descent part. Upon close observation, however, you will notice that each generation is different from the one proceeding; that is, the generations are not simply exact copies of each other. This is the modification part. A more modern definition of evolution would be "any change in the gene frequencies of a population with time" (modified from Wilson and Bossert 1971). Both definitions are, however, essentially the same.
Why does evolution occur? This is where theory comes in, and there are many theories of what might cause changes in gene frequencies in populations with time. An older theory, familiar to most people, is the theory of the great French scientist Lamarck, which we might call the "theory of the genetic inheritance of acquired phenotypic characteristics." This is a little long, but it sums up the idea. And it is a very respectable scientific theory of why evolution takes
place, it has predictions, and it is subject to test (i.e., it is verifiable). It was tested and found not to work. That is the fate of most scientific theories, but without the constant proposing and testing of theories science would make no progress. Thus Lamarck's theory was, and is,
important to science.
When you encounter the headline "Scientists Debate the Theory of Evolution," the immediate implication is that evolution itself is being called into question. This is not the case, and journalists do a disservice to both science and the public in running such headlines. In most instances what is being debated is the applicability of one or more theories or models of how evolution actually takes place, such as the debate concerning the phyletic gradualist model of evolutionary change versus the punctuated equilibrial model. Or the debate between neutralist and selectionist models of evolution. The most widely subscribed-to theory of how evolution takes place is that of natural selection, first proposed by Charles Darwin. If he had not gotten around to proposing it, Alfred Wallace would have instead; thus it was clearly an idea whose time had come in the 1800s. What is natural selection? A precise, rather pithy definition is the
"differential change in genotypic frequencies with time, due to the page 248 differential reproductive success of their phenotypes" (modified from Wilson and Bossert 1971). The first part of the definition is simply a restatement of the definition of evolution itself. The real heart of the theory is differential reproductive success. If certain organisms in a population reproduce at a higher rate than other organisms, then the next generation will contain more of their genes than the previous one. And that change in gene frequencies, from generation 1 to generation 2, is by definition evolution. Thus natural selection could clearly drive evolution. The definition of natural selection does not specify what causes differential reproductive success; it simply holds that if it does occur, evolution will result. The next question is obvious: "What could determine the differential reproductive success of differing phenotypes, and why do different animals and plants reproduce at different rates?"
********************************************
I think he's wrong about who would press the key first though, because I think I would be the first to press it.
George McGhee, Jr is the first person, who I have seen, to get it right. Other people have stated that Evolution is both a theory and a fact, which is incorrect.
*********************************************
In his book The Late Devonian Mass Extinction, George R. McGhee, Jr. writes (bolding and coloring added by me):
EVOLUTION IS a fact. It is an empirical observation, not a theory. Life has evolved in the past and is still evolving today. Visit the laboratory of any population geneticist or ecologist today and you will be shown evolutionary change in the organisms they studied in the modern world. Visit the laboratories or field sites of paleontologists and you will be shown the actual record of the evolution of life in the past.
Imagine a bright red key on the keyboard of a supermegacomputer that, if pressed, would erase the phrase "theory of evolution" from the literature everywhere. I would be the first to press that key. That phrase has caused enormous confusion, especially for the general
public. I would replace it with phrases like "theories of why evolution takes place" or "theories of how evolution works" instead, with emphasis on the plural, as that is what is really meant. In fact, the great majority of times you encounter the phrase "the theory of evolution" in the popular literature what is actually meant is "the theory of natural selection."
page 247
What is evolution? In Charles Darwin's time, a general definition would have been "descent with modification." And that is not a bad definition. It means that one generation of animals or plants produces the next generation of offspring, which in turn produces the next generation, and so on. This is the descent part. Upon close observation, however, you will notice that each generation is different from the one proceeding; that is, the generations are not simply exact copies of each other. This is the modification part. A more modern definition of evolution would be "any change in the gene frequencies of a population with time" (modified from Wilson and Bossert 1971). Both definitions are, however, essentially the same.
Why does evolution occur? This is where theory comes in, and there are many theories of what might cause changes in gene frequencies in populations with time. An older theory, familiar to most people, is the theory of the great French scientist Lamarck, which we might call the "theory of the genetic inheritance of acquired phenotypic characteristics." This is a little long, but it sums up the idea. And it is a very respectable scientific theory of why evolution takes
place, it has predictions, and it is subject to test (i.e., it is verifiable). It was tested and found not to work. That is the fate of most scientific theories, but without the constant proposing and testing of theories science would make no progress. Thus Lamarck's theory was, and is,
important to science.
When you encounter the headline "Scientists Debate the Theory of Evolution," the immediate implication is that evolution itself is being called into question. This is not the case, and journalists do a disservice to both science and the public in running such headlines. In most instances what is being debated is the applicability of one or more theories or models of how evolution actually takes place, such as the debate concerning the phyletic gradualist model of evolutionary change versus the punctuated equilibrial model. Or the debate between neutralist and selectionist models of evolution. The most widely subscribed-to theory of how evolution takes place is that of natural selection, first proposed by Charles Darwin. If he had not gotten around to proposing it, Alfred Wallace would have instead; thus it was clearly an idea whose time had come in the 1800s. What is natural selection? A precise, rather pithy definition is the
"differential change in genotypic frequencies with time, due to the page 248 differential reproductive success of their phenotypes" (modified from Wilson and Bossert 1971). The first part of the definition is simply a restatement of the definition of evolution itself. The real heart of the theory is differential reproductive success. If certain organisms in a population reproduce at a higher rate than other organisms, then the next generation will contain more of their genes than the previous one. And that change in gene frequencies, from generation 1 to generation 2, is by definition evolution. Thus natural selection could clearly drive evolution. The definition of natural selection does not specify what causes differential reproductive success; it simply holds that if it does occur, evolution will result. The next question is obvious: "What could determine the differential reproductive success of differing phenotypes, and why do different animals and plants reproduce at different rates?"
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I think he's wrong about who would press the key first though, because I think I would be the first to press it.
1 comment:
Great work.
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