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Evolution Essay, Research Paper
Theories explaining biological evolution have been bandied about since
the ancient Greeks, but it was not until the Enlightment of the 18th
century that widespread acceptance and development of this theory emerged.
In the mid 19th century english naturalist Charles Darwin – who has been
called the “father of evolution” – conceived of the most comprehensive
findings about organic evolution ever1. Today many of his principles still
entail modern interpretation of evolution.
I’ve assessed and interpreted the basis of Darwin’s theories on
evolution, incorporating a number of other factors concerning evolutionary
theory in the process. Criticism of Darwin’s conclusions abounds somewhat
more than has been paid tribute to, however Darwin’s findings marked a
revolution of thought and social upheaval unprecedented in Western
consciousness challenging not only the scientific community, but the
prominent religious institution as well. Another revolution in science of
a lesser nature was also spawned by Darwin, namely the remarkable
simplicity with which his major work The Origin of the Species was written
- straightforward English, anyone capable of a logical argument could
follow it – also unprecedented in the scientific community (compare this to
Isaac Newton’s horribly complex work taking the scientific community years
Evolutionary and revolutionary in more than one sense of each word.
Every theory mentioned in the following reading, in fact falls back to
DARWINIAN THEORY OF BIOLOGICAL EVOLUTION
Modern conception of species and the idea of organic evolution had
been part of Western consciousness since the mid-17th century (a la John
Ray)3, but wide-range acceptance of this idea, beyond the bounds of the
scientific community, did not arise until Darwin published his findings in
19584. Darwin first developed his theory of biological evolution in 1938,
following his five-year circumglobal voyage in the southern tropics (as a
naturalist) on the H.M.S. Beagle, and perusal of one Thomas Malthus’ An
Essay on the Principle of Population which proposed that environmental
factors, such as famine and disease limited human population growth5. This
had direct bearing on Darwin’s theory of natural selection, furnishing him
with an enhanced conceptualization of the “survival of the fittest” – the
competition among individuals of the same species for limited resources -
the “missing piece” to his puzzle6. For fear of contradicting his father’s
beliefs, Darwin did not publish his findings until he was virtually forced
after Alfred Wallace sent him a short paper almost identical to his own
extensive works on the theory of evolution. The two men presented a joint
paper to the Linnaean Society in 1958 – Darwin published a much larger work
(”a mere abstract of my material”) Origin of the Species a year later, a
source of undue controversy and opposition (from pious Christians)7, but
remarkable development for evolutionary theory.
Their findings basically stated that populations of organisms and
individuals of a species were varied: some individuals were more capable of
obtaining mates, food and other means of sustenance, consequently producing
more offspring than less capable individuals. Their offspring would retain
some of these characteristics, hence a disproportionate representation of
successive individuals in future generations. Therefore future generations
would tend have those characteristics of more accommodating individuals8.
This is the basis of Darwin’s theory of natural selection: those
individuals incapable of adapting to change are eliminated in future
generations, “selected against”. Darwin observed that animals tended to
produce more offspring than were necessary to replace themselves, leading
to the logical conclusion that eventually the earth would no longer be able
to support an expanding population. As a result of increasing population
however, war, famine and pestilence also increase proportionately,
generally maintaining comparatively stable population9.
Twelve years later, Darwin published a two-volume work entitled The
Descent of Man, applying his basic theory to like comparison between the
evolutionary nature of man and animals and how this related to socio-
political development man and his perception of life. “It is through the
blind and aimless progress of natural selection that man has advance to his
present level in love, memory, attention, curiosity, imitation, reason, etc.
as well as progress in “knowledge morals and religion”10. Here is where
originated the classic idea of the evolution of man from ape, specifically
where he contended that Africa was the cradle of civilization. This work
also met with opposition but because of the impact of his “revolutionary”
initial work this opposition was comparatively muted11.
A summary of the critical issues of Darwin’s theory might be abridged
into six concise point as follows: 1 Variation among individuals of a
species does not indicate deficient copies of an ideal prototype as
suggested by the
platonic notion of Eidos. The reverse is true: variation is integral
to the evolutionary process.
2 The fundamental struggle in nature occurs within single species
population to obtain food, interbreed, and resist predation. The struggle
between different species (ie. fox vs. hare) is less consequential.
3 The only variations pertinent to evolution are those which are
4 Evolution is an ongoing process which must span many moons to become
5 Complexity of a species may not necessarily increase with the
evolutionary process – it may not change at all, even
6 Predator and prey have no underlying purpose for maintenance of any
type of balance – natural selection is opportunistic and irregular12.
THE THEORY OF BIOLOGICAL EVOLUTION: CONTRIBUTING ELEMENTS
The scientific range of biological evolution is remarkably vast and
can be used to explain numerous observations within the field of biology.
Generally, observation of any physical, behaviourial, or chemical change
(adaptation) over time owing directly to considerable diversity of
organisms can be attributed to biological evolution of species. It might
also explain the location (distribution) of species throughout the planet.
Naturalists can hypothesize that if organisms are evolving through
time, then current species will differ considerably from their extinct
ancestors. The theory of biological evolution brought about the idea for a
record of the progressive changes an early, extinct species underwent.
Through use of this fossil record paleontologists are able to classify
species according to their similarity to ancestral predecessors, and
thereby determine which species might be related to one another.
Determination of the age of each fossil will concurrently indicate the rate
of evolution, as well as precisely which ancestors preceded one another and
consequently which characteristics are retained or selected against.
Generally this holds true: probable ancestors do occur earlier in the
fossil record, prokaryotes precede eukaryotes in the fossil record. There
are however, significant “missing links” throughout the fossil record
resulting from species that were, perhaps, never fossilized – nevertheless
it is relatively compatible with the theory of evolution13.
It can be postulated that organisms evolving from the same ancestor
will tend to have similar structural characteristics. New species will have
modified versions of preexisting structures as per their respective
habitats (environmental situations). Certainly these varying species will
demonstrate clear differentiation in important structural functions,
however an underlying similarity will be noted in all. In this case the
similarity is said to be homologous, that is, structure origin is identical
for all descended species, but very different in appearance. This can be
exemplified in the pectoral appendages of terrestrial vertebrates: Initial
impression would be that of disparate structure, however in all such
vertebrates four distinct structural regions have been defined: the region
nearest the body (humerus connecting to the pectoral girdle, the middle
region (two bones, radius and ulna are present), a third region – the
“hand” – of several bones (carpal and metacarpal, and region of digits or
“fingers”. Current species might also exhibit similar organ functions, but
are not descended from the same ancestor and therefore different in
structure. Such organisms are said to be analogous and can be exemplified
in tetrapods, many containing similar muscles but not necessarily
originating from the same ancestor. These two anatomical likenesses cannot
be explained without considerable understanding of the theory of organic
The embryology, or early development of species evolved from the same
ancestor would also be expected to be congruent. Related species all share
embryonic features. This has helped in determining reasons why development
takes place indirectly, structures appearing in embryonic stage serve no
purpose, and why they are absent in adults. All vertebrates develop a
notchord, gill slits (greatly modified during the embryonic cycle) and a
tail during early embryology, subsequently passing through stages in which
they resemble larval amphioxus, then larval fishes. The notchord will only
be retained as discs, while only the ear canal will remain of the gills in
adults. Toothless Baleen whales will temporarily develop teeth and hair
during early embryology leading to the conclusion that their ancestors had
these anatomical intricacies. A similar pattern, exists in almost all
animal organisms during the embryonic stage for numerous formations of
common organs including the lungs and liver. Yet there is a virtually
unlimited variation of anatomical properties among adult organisms. This
variation can only be attributed to evolutionary theory15.
Biological evolution theory insists that in the case of a common
ancestor, all species should be similar on a molecular level. Despite the
tremendous diversity in structure, behaviour and physiology of organisms,
there is among them a considerable amount of molecular consistency. Many
statements have already been made to ascertain this: All cells are
comprised of the same elemental organic compounds, namely proteins, lipid
and carbohydrates. All organic reactions involve the action of enzymes.
Proteins are synthesized in all cells from 20 known amino acids. In all
cells, carbohydrate molecules are derivatives of six-carbon sugars (and
their polymers). Glycolysis is used by all cells to obtain energy through
the breakdown of compounds. Metabolism for all cells as well as
determination of definitude of proteins through intermediate compounds is
governed by DNA. The structure for all vital lipids, proteins, some
important co-enzymes and specialized molecules such as DNA, RNA and ATP are
common to all organisms. All organisms are anatomically constructed through
function of the genetic code. All of these biochemical similarities can be
predicted by the theory of biological evolution but, of course some
molecular differentiation can occur. What might appear as minor
differentiation (perhaps the occurrence-frequency of a single enzyme) might
throw species into entirely different orders of mammals (ie. cite the
chimpanzee and horse, the differentiation resulting from the presence of an
extra 11 cytochrome c respiratory enzymes). Experts have therefore
theorized that all life evolve from a single organism, the changes having
occurred in each lineage, derived in concert from a common ancestor16.
Breeders had long known the value of protective resemblance long
before Darwin or any other biological evolution theorists made their mark.
Nevertheless, evolutionary theory can predict and explain the process by
which offspring of two somewhat different parents of the same species will
inherit the traits of both – or rather how to insure that the offspring
retains the beneficial traits by merging two of the same species with like
physical characteristics. It was the work of Mendel that actually led to
more educated explanations for the value in protective resemblance17. The
Hardy-Weinburg theory specifically, employs Mendel’s theory to a degree to
predict the frequency of occurrence of dominantly or recessively expressing
offspring. Population genetics is almost sufficient in explaining the basis
for protective resemblance. Here biological evolutionary theory might
obtain its first application to genetic engineering18.
Finally, one could suggest that species residing in a specific area
might be placed into two ancestral groups: those species with origins
outside of the area and those species evolving from ancestors already
present in the area. Because the evolutionary process is so slow, spanning
over considerable lengths of time, it can be predicted that similar species
would be found within comparatively short distances of each other, due to
the difficulty for most organisms to disperse across an ocean. These
patterns of dispersion are rather complex, but it is generally maintained
by biologists that closely related species occur in the same indefinite
region. Species may also be isolated by geographic dispersion: they might
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