Click on images to see animations.
My enhanced version of NASA's image.
Original image from NASA.
Monday, March 5, 2007
Tuesday, February 6, 2007
The Fact of Evolution
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.
*********************************************
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?"
********************************************
I think he's wrong about who would press the key first though, because I think I would be the first to press it.
Monday, February 5, 2007
Why?
Evolution provides the answer to why things are the way they are. If you never learn evolution then you'll never know the answer to the question of why.
Humans are mammals. Mammals are endothermic (they generate heat). Heat is needed to sustain the chemical reactions for life. Up to 90 percent of the metabolic energy used in mammals is used to generate heat.
Lizards are ectothermic. They get most of their heat from their environment. They bask in the sun in the morning to warm up. Lizards also lose excess heat to their environment. Raymond Cowles demonstrated in the 1930s that a lizard can not wear a fur coat because it would interfere with their heat exchanging capabilities with their environment. A fur coat can not keep a lizard warm because they can’t get warm in the first place with a coat on. Since mammals produce their own heat they use hair to insulate themselves from heat loss.
A lizard uses 10 times less energy than a mammal of the same size. A lizard eats 10 times less food than a mammal of the same size.
The prevalent conditions on Earth for the past 40 million years have been cold and the period is referred to as "Ice House" conditions. The Polar caps first formed 40 million years ago.
Mammals have proliferated during the past 40 million years and now have a ubiquitous presence on Earth today. The Cenozoic is known as "the Age of Mammals", because of their rapid evolution to fill niches that were vacated during the KT mass extinction.
The endothermic capabilities of mammals make them the perfect inhabitants of cold Earth. As the Earth warms up mammals will need to evolve into new forms to cope with the increasing heat. If the heating is too rapid then species will not have time to evolve and will become extinct. Anthropogenic (human) activities are accelerating the change in climate and the effect is known as Anthropogenic Global Warming.
The climate has always changed on Earth but the rate of change has never been affected by a species to the extent that humans have. If the polar caps melt then the 40 million year “Ice House” will come to an end. This would be an entirely artificial climate produced by humans. We are destroying the habitability of Earth for mammals.
Humans are mammals. Mammals are endothermic (they generate heat). Heat is needed to sustain the chemical reactions for life. Up to 90 percent of the metabolic energy used in mammals is used to generate heat.
Lizards are ectothermic. They get most of their heat from their environment. They bask in the sun in the morning to warm up. Lizards also lose excess heat to their environment. Raymond Cowles demonstrated in the 1930s that a lizard can not wear a fur coat because it would interfere with their heat exchanging capabilities with their environment. A fur coat can not keep a lizard warm because they can’t get warm in the first place with a coat on. Since mammals produce their own heat they use hair to insulate themselves from heat loss.
A lizard uses 10 times less energy than a mammal of the same size. A lizard eats 10 times less food than a mammal of the same size.
The prevalent conditions on Earth for the past 40 million years have been cold and the period is referred to as "Ice House" conditions. The Polar caps first formed 40 million years ago.
Mammals have proliferated during the past 40 million years and now have a ubiquitous presence on Earth today. The Cenozoic is known as "the Age of Mammals", because of their rapid evolution to fill niches that were vacated during the KT mass extinction.
The endothermic capabilities of mammals make them the perfect inhabitants of cold Earth. As the Earth warms up mammals will need to evolve into new forms to cope with the increasing heat. If the heating is too rapid then species will not have time to evolve and will become extinct. Anthropogenic (human) activities are accelerating the change in climate and the effect is known as Anthropogenic Global Warming.
The climate has always changed on Earth but the rate of change has never been affected by a species to the extent that humans have. If the polar caps melt then the 40 million year “Ice House” will come to an end. This would be an entirely artificial climate produced by humans. We are destroying the habitability of Earth for mammals.
Monday, January 29, 2007
Crossbedded Jurassic Navajo Sandstone
Starting at GPS 37.13843N 112.56629W on route 89 in Southern Utah and driving south, I encountered massive crossbedded sandstone. The picture above is at the GPS point looking east (I waited for the truck for scale). The first two images are just south of this point on route 89. This is in Utah just 9 miles north of the Utah/Arizona border.
Below is an excerpt from the USGS report of an area 15 miles south of this spot. A lot of petrology books that I have read that introduce sedimentary rocks show the crossbedded Navajo Sandstone, so I recognized it as soon as I seen it.
Excerpt from USGS report on Mohave County, Arizona
SEDIMENTARY ROCKS Navajo Sandstone (Lower Jurassic)—White to light-red and yellow-gray, cliff-forming, medium-crossbedded to thickly-crossbedded, well-sorted, fine- to coarse-grained eolian quartz sandstone interbedded with dark-red, coarse-grained sandstone and siltstone in lower part. Age determination by Peterson and Pipiringos (1979) and Biek and others (2000). Lower part is commonly red, upper part commonly white. Includes lenses of interbedded dark purple-gray, thin-bedded, calcareous sandstone beds that formed freshwater deposits within and between coastal sand dunes. High-angle, crossbedded sandstone sets interbedded with low-angle, crossbedded sandstone and thin flat-bedded sandstone sets.
Excerpt from USGS report on Mohave County, Arizona
SEDIMENTARY ROCKS Navajo Sandstone (Lower Jurassic)—White to light-red and yellow-gray, cliff-forming, medium-crossbedded to thickly-crossbedded, well-sorted, fine- to coarse-grained eolian quartz sandstone interbedded with dark-red, coarse-grained sandstone and siltstone in lower part. Age determination by Peterson and Pipiringos (1979) and Biek and others (2000). Lower part is commonly red, upper part commonly white. Includes lenses of interbedded dark purple-gray, thin-bedded, calcareous sandstone beds that formed freshwater deposits within and between coastal sand dunes. High-angle, crossbedded sandstone sets interbedded with low-angle, crossbedded sandstone and thin flat-bedded sandstone sets.
Friday, January 26, 2007
Barringer Crater or Meteor Crater
I visited Meteor Crater in Arizona in June of 2006.
GPS position 35.02744893 -111.0229199
Here are two videos that I made of the guided tour and posted on youtube.
Barringer Meteor Crater Tour Intro
Barringer Meteor Crater Tour
Thursday, January 25, 2007
Currently Reading VERTEBRATE LIFE
I am currently reading VERTEBRATE LIFE 6th ed. I am reading Chapter 15: The Evolution of Birds and the Origin of Flight.
Archaeopteryx lithographica is the earliest known bird. In the fossil above the feathers are preserved due to the very fine grained sediment of lithographic limestone in which it was found in Germany.
Birds are dinosaurs.
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