HPAVC/HPAVC CD-ROM.iso/pc/HOMEWORK.ZIP/GEOEVOB.TXT

Text File | 1998-07-25 | 7.2 KB | 98 lines

Review and Summary of
S. J. Gould's
The Evolution of Life on the Earth
By Scott Gilstrap


 Evolution of life on Earth, is not a progressive, constant development of species striving
 for perfection, as commonly believed.   Human existence is by lucky chance, not by design.
 Although, much of this article is well over my understanding, this seems to be his
 reoccurring theme.  Gould wants us (as a society), to take an entirely different approach
 to how we view evolution.  We should realize that we (as humans) are not the end product,
 but rather a fortuitous incident. Natural selection, defined by Darwin, represents the
 evolutionary change in the "struggle" from all living things, to reproduce.  The word
 "struggle", is often misinterpreted as "...overt combat, guns blazing."  Successful
 reproduction is achieved through means of adaptation, such as mating more frequent, and
 enhanced cooperation within a species.  Natural selection is therefore, a product of
 adaptation, not advancement, or progression.  As well, natural selection should not be
 considered the only cause of evolutionary change.  Even Darwin recognized this, and placed
 a caveat at the end of his introduction; "I am convinced that Natural Selection has been
 the most important, but not the exclusive, means of modification."
There are two major reasons why natural selection isn't capable of all evolutionary change.
First, there are other powerful causes that force change, both at the biological levels,
such as random change in DNA, and mass extinctions  which wipe out entire species for
reasons unrelated to the adaptive struggle.  Second, The chaos, and "webs and chains of
historical events" are so random, and minute, it would be impossible for replication, or
prediction.  Gould gives an example of this, by citing 4 events, that if they occurred
differently (or not at all), the human race would be non-existent.  1. If our inconspicuous
and fragile lineage had not been one of the few survivors of the initial radiation of
multicellular animal life in the Cambrian explosion 530 million years ago, then no
vertebrates would have inhabited the earth at all.  Only one chordate phylum, the genus
Pikaia, has been found among these early fossils. 2. If the lobe-finned fishes had not
evolved fin bones with a strong central axis capable of bearing weight on land, then
vertebrates might never have become terrestrial. 3. If a large extra-terrestrial body had
not struck the earth 65 million years ago, then dinosaurs would still be dominant and
mammals insignificant (the situation that prevailed for 100 million years previously). 4. If
a small lineage of primates had not evolved upright posture on the drying African savannas
just two to four million years ago, then our ancestry might have ended in a line of apes
that, like the chimpanzee and gorilla today, would have become ecologically marginal and
probably doomed to extinction despite their remarkable behavioral complexity. (Gould, 86)

 We must look beyond contemporary evolutionary theory to a more paleontological viewpoint.
 We must examine the actual version of our evolutionary pathway, which among all the other
 possible alternatives that did no occur, would seem unlikely to succeed.  We have gone
 through the "age of invertebrates", the "age of fishes", the "age of reptiles", the "age of
 mammals", and to the "age of man".  Our categorization of these ages seem to represent a
 progression of evolution, and mankind to be dominant.  Gould states in his article that
 this is a gross distortment of  the pathway of life, by placing such emphasis on the
 centering of mankind.  He states that this is truly, the "age of the bacteria - as it was
 in the beginning, is now and ever shall be."  Occasionally (albeit rare and episodic), a
 more complex creature evolves, and the range of evolutionary diversity increases.  However,
 bacteria represents the true success story of evolution.  They have weathered all tests,
 survived all of natures experiments, and have proven to be indestructible, adaptable, and
 amazingly diverse.  The Cambrian explosion, which took place 530 million years ago, was the
 "most remarkable and puzzling event in the history of life." (Gould 89)  This was a period
 of about five million years, when the evolution of new life forms went through a
 spectacular leap.  Many new and highly unusual life forms appeared at an unbelievable rate.
  Gould offers an "external" explanation, which is represented by an "ecological barrel" for
 multicellular organisms, which any of natures experiments found space in the barrel.  An
 "internal" explanation, he states, is based on genetics.    The animals transformation
 maintained flexible genetic structure, then became "locked in" to stable and successful
 designs.  Regardless, this explosion created a much broader range of life than exists
 today.  Many of these life forms simply went away shortly after the explosion, and only a
 few survived to become our modern phyla.  This would make it seem then that winners of this
 race is because of their virtue of greater complexity.  Gould cautions us from that line of
 thinking.  The victors received nothing more than a winning ticket in the "largest lottery
 ever played out on our planet" (Gould, 89)  Each surviving phyla are alive today by mere
 luck of the draw, not because of any progressive struggle for existence.  In fact, the
 history of animal life, is more based on reduction of possibilities, and stabilization of
 the lucky survivors, rather than the accepted belief of continuous expansion and progress
 in complexity.  Often, humans place overemphasis on surviving the dinosaur, because of some
 superiority.  This is highly unlikely.  Mammals and dinosaurs lived with each other for
 almost about 100 million years, mammals (which at the time where small rat sized creatures)
 had made no evolutionary attempt to evict the dinosaurs.  No one has ever successfully
 advanced an argument for general superiority of mammals, and simple luck seems the only
 answer.  One possible argument for the surviving of the mammals, are the fact that they
 were so small, having more places to hide, and nourish themselves.  Gould also states that
 small size wasn't a positive adaptation, but a sign of inability to dominate the dinosaurs.
  "Yet this negative feature of normal times may be the key reason for mammalian survival."
 (Gould 91).  Sigmund Freud once noted that "great revolutions in the history of science
 have but one common, and ironic, feature:  they knock human arrogance off one pedestal
 after another of our own previous conviction about our own self-importance." (Gould 91)
 The Darwinian revolution has never bore fruit yet, because of the unwilling of most of us
 to release the comfortable view of evolution as progress, defined to render the appearance
 of something with human-like consciousness.  Human beings, must except the fact that we are
 "but a tiny, late-arising twig on life's enormously arborescent bush - a small bud that
 would almost surely not appear a second time if we could replant  the bush from seed and
 let it grow again." (Gould 91)



Reference

S.J. Gould: The Evolution of Life on the Earth.  Scientific American, October 1994: 85-91.