The traditional view of the march of life toward ever increasing complexity, culminating in the emergence of homo sapiens some 50, years ago, is a misinterpretation of how evolution actually works. Intelligence, in particular, should not be seen as the culmination of the evolutionary process. In evolutionary terms, the higher animals are in no way better adapted than bacteria or plants.
Our line of hominids is the outcome of one of Nature's myriad random experiments, and until quite recently we remained just a curiosity among the millions of animal species. There are many intelligent animals. Consider the cuckoo which lays its egg among other eggs in a nest of a different bird species. The cuckoo egg hatches before the others, and the first thing the newborn cuckoo does, is to kick the other eggs out of the nest, thus eliminating competition for its foster parents' care.
But this is hard-wired intelligence, pure instinct. In all probability, the young cuckoo has no sense of purpose. Simon Conway Morris, one of the heroes in Gould's book, points to functional convergence among different species as support for his view that regardless of genetic makeup, evolution does have a trend. Birds and bats are quite different groups, yet they have evolved wings for flight. Fish and dolphins have similar shapes, etc.
Also, since Gould's book was written, many more fossils have been found and analysed. The Cambrian Explosion may have been a little more gradual and less explosive than previously thought, and the view that a large number of fundamentally different forms of life went extinct in short order has been criticized. Gould, who was a brilliant writer and speaker with a large audience, has been vilified as "the Sagan of the geosciences".
Carl Sagan was an astronomer with a gift for making science understandable and exciting to the general public. He held the opposite view from Gould on the prospects for intelligent life in our galaxy. In addition, Gould, as a confirmed atheist and socialist, predictably triggered some strong animosity among religious and political opponents. I must confess that during most of my adult life, I have accepted Darwinian theory without much thought, taking comfort in the implied view that evolution must have led to the emergence of countless intelligent and conscious creatures in the universe.
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Gould's view of the history of life as a fundamentally random process has certainly given me pause. They argue persuasively, that far from the gradual, more or less predictable, progress of life from simple bacteria to homo sapiens that most of us have come to associate with Darwinism, complex life on Earth is in fact a result of a wildly improbable sequence of accidents. The good news is that simple bacterial life seems likely to occur on innumerable worlds. We might yet discover alien forms of life in our own Solar system. Ward and Brownlee are encouraged by the early development of life on Earth shortly after our planet's surface had solidified and cooled down to the boiling point of water.
Also, the recent discovery of extreme microbes near deep-sea volcanic vents indicates that solar energy may not be necessary for life.
These "archeans" seem to be a more primitive life form than bacteria and may have survived repeated sterilizations of the Earth's surface. Once bacterial life is established, it is extremely difficult to stamp out. Ward thinks that there is a distinct possibility that alien bacterial life exists in the Solar system. He is critical of the fact that NASA's Genesis mission, which brought a sample of solar wind to the Earth in , was not adequately protected from potentially infecting us with dangerous microbes.
Wonderful Life:The Burgess Shale and the Nature of History
In contrast, the evolution of complex life, such as animals, has been possible only due to an improbable chain of favorable circumstances. Earth life as we know it would not have been possible if our sun had not been of the right size to burn steadily for billions of years, and the Earth located far enough from the galactic center to be reasonably safe from cosmic radiation from energetic events and nearby supernovae. A little closer to the Sun and the climate would be too hot.
A little farther out and our planet would be frozen. Water probably was brought to the Earth by comet impacts. Throughout its history, our planet has been pummeled by asteroid and comet impacts.
Wonderful life : the Burgess Shale and the nature of history / Stephen Jay Gould
Our moon was created from the collision of a Mars-sized planetoid with the Earth. During the heaviest bombardment, which occurred early in Earth's history, its surface may have melted repeatedly. Any oceans would have been vaporized. As recently as 65 million years ago, the Earth was hit by an object that created a km diameter impact crater and caused the extinction of the dinosaurs.
A more severe extinction event occurred million years ago, when 90 percent of all marine species died out. Yet, the Earth may have been fortunate. Simulations indicate that there would be many more objects crossing the Earth's orbit if the giant planet Jupiter had not been available at just the right distance from the sun. Jupiter absorbs or deflects comets and asteroids through its strong gravitational pull, sending some of them off into interstellar space, others on a collision trajectory with the sun.
When sedimentary rocks are subducted deep into the mantle, carbon dioxide is returned to the atmosphere. This tends to warm a planet that would otherwise become progressively colder. Of course, this "Goldilocks theory" that the Earth is just right for complex life while few other planets are likely to be similarly favored is far from universally agreed upon.
Wonderful Life: The Burgess Shale and the Nature of History - Stephen Jay Gould - Google книги
It is awfully risky to base a statistical argument on a sample of one. Until recently we had no idea that there is primitive life powered by volcanic vents on the sea floor, and life itself may find ways to evolve which we cannot imagine. As long as there is a sense of direction and purpose to biological evolution, most of us are willing to accept it as a well-established fact.
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- Genetic Mechanisms of Speciation in Insects: Symposia held at the XIVth International Congress of Entomology, Canberra, Australia August 22–30, 1972, sponsored by the Australian Academy of Science and the Australian Entomological Society.
Although one of my nieces as a child said: Dad says that we come from apes, and apes came from dinosaurs. But where did the dinosaurs come from? Nah, I still think God did it. Even the Pope now embraces evolution. It is the view of evolution as a random process without direction or purpose that is creating resistance even among educated people.
But it is interesting that Mark Twain wrote: If the Eiffel Tower were now representing the world's age, the skin of paint on the pinnacle knob at its summit would represent man's share of that age; and anybody would perceive that the skin was what the tower was built for. I reckon they would, I dunno. Darwin was ambiguous on this matter. He acknowledged the existence of general laws that regulate life in a broad sense. Sign In. View the Study Pack. View the Lesson Plans. Plot Summary. Chapter 1, The Iconography of an Explanation.
Chapter 2, A Background for the Burgess Shale. The Burgess Drama, Act I.
https://ringdederough.ml The Burgess Drama, Act 2. The Burgess Drama, Act 3. The Burgess Drama, Act 4. Completion and Codiication of an Argument: Naraoia and Aysheaia, The Burgess Drama, Act 5. Remainder of Chapter 3.
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