Evolution2

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evolution2



INTRODUCTION


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
to interpret2).
Evolutionary and revolutionary in more than one sense of each word.
Every theory mentioned in the following reading, in fact falls back to
Darwinism.
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
inherited.

4 Evolution is an ongoing process which must span many moons to become
detectably apparent.

5 Complexity of a species may not necessarily increase with the
evolutionary process - it may not change at all, even
decrease.

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
evolution14.
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
colonize an island, and over the course of time evolve differently from
their relatives on the mainland. Madagascar is one such example - in fact
approximately 90 percent of the birds living there are endemic to that
region. Thus as predicted, it follows that speciation is concurrent with
the theory of biological evolution19.
WALLACE'S CONTRIBUTIONS


There is rarely a sentence written regarding Wallace that does not
contain some allusion to Darwin. Indeed, perhaps the single most
significant feat he preformed was to compel Darwin to enter the public
scene20. Wallace, another English naturalist had done extensive work in
South America and southeast Asia (particularly the Amazon and the Malay
Archipelago) and, like Darwin, he had not conceived of the mechanism of
evolution until he read (recalled, actually) the work of Thomas Malthus -
the notion that "in every generation the inferior would be killed off and
the superior would remain - that is the fittest would survive". When the
environment changed therefore, he determined "that all the changes
necessary for the adaptation of the species ... would be brought about; and
as the great changes are always slow there would be ample time for the
change to be effected by the survival of the best fitted in every
generation". He saw that his theory supplanted the views of Lamarck and
the Vistages and annulled every important difficulty with these theories21.
Two days later he sent Darwin (leading naturalist of the time) a four-
thousand word outline of his ideas entitled "On the Law Which has Regulated
the Introduction". This was more than merely cause for Darwin's distress,
for his work was so similar to Darwin's own that in some cases it
parallelled Darwin's own phrasing, drawing on many of the same examples
Darwin hit upon. Darwin was in despair over this, years of his own work
seemed to go down the tube - but he felt he must publish Wallace's work.
Darwin was persuaded by friends to include extracts of his own findings
when he submitted Wallace's work On the Law Which Has Regulated the
Introduction of New Species to the Linnaean Society in 1858, feeling doubly
horrible because he felt this would be taking advantage of Wallace's
position. Wallace never once gave the slightest impression of resentment
or disagreement, even to the point of publishing a work of his own entitled
Darwinism. This itself was his single greatest contribution to the field:
encouraging Darwin to publish his extensive research on the issues they'd
both developed22.
He later published Contributions to the Theory of Natural Selection,
comprising the fundamental explanation and understanding of the theory of
evolution through natural selection. He also greatly developed the notion
of natural barriers which served as isolation mechanisms, keeping apart not
only species but also whole families of animals - he drew up a line
("Wallace's line") where the fauna and flora of southeast Asia were very
distinct from those of Australasia23.
HARDY-WEINBERG PRINCIPLE


Prior to full recognition of Mendel's work in the early 1900's,
development of quantitative models describing the changes of gene
frequencies in population were not realized. Following this "rediscovery"
of Mendel, four scientists independently, almost simultaneously contrived
the Hardy-Weinberg principal (named after two of the four scientists) which
initiated the science of population genetics: exploration of the
statistical repercussions of the principle of inheritance as devised by
Mendel. Read concisely the Hardy-Weinberg principle might be stated as
follows: Alternate paradigms of genes in ample populations will not be
modified proportionately as per successive generation, unless stimulated by
mutation, selection, emigration, or immigration of individuals. The
relative proportion of genotypes in the population will also be maintained
after one generation, should these conditions be negated or mating is
random24.

Through application of the Hardy-Weinberg principle the precise
conditions under which change does not occur in the frequencies of alleles
at a locus in a given population (group of individuals able to interbreed
and produce fertile offspring) can be formulated: the alleles of a locus
will be at equilibrium. A species may occur in congruous correspondence
with its population counterpart, or may consist of several diverse
populations, physically isolated from one another25.
In accordance with Mendelian principle, given two heterozygous alleles
A and B, probability of the offspring retaining prominent traits of either
parent (AA or BB) is 25 percent, probability of retaining half the traits
of each parent (AB) is 50 percent. Thus allele frequencies in the
offspring parallel those of the parents. Likewise, given one parent AB and
another AA, allele frequencies would be 75 percent A and 25 percent B,
while genotype frequencies would be 50 percent AA and 50 percent AB - the
gametes generated by these offspring would also maintain the same ratio
their parents initiated (given, of course a maximum of two alleles at each
locus).
In true-to-life application however, where numerous alleles may occur
at any given locus numerous possible combinations of gene frequencies are
generated. Assuming a population of 100 individuals = 1, 30 at genotype AA,
70 at genotype BB. Applying the proportionate theory, only 30% (0.30) of
the gametes produced will retain the A allele, while 70% (0.70) the B
allele. Assuming there is no preference for AA or BB individuals for mates,
the probability of the (30% of total population) AA males mating with AA
females is but 9% (0.3 x 0.3 = 0.09). Likewise the probability of an BB to
BB match is 49%, the remainder between (30%) AA and (70%) BB individuals,
totalling a 21% frequency. Frequency of alleles in a population in are
commonly denoted p and q respectively, while the AB genotype is denoted
2pq. Using the relevant equation p pq q = 1, the same proportions
would be obtained. It can therefore be noted that the frequencies of the
alleles in the population are unchanged. If one were to apply this equation
to the next generation, similarly the genotype frequencies will remain
unchanged per each successive generation. Generally speaking, the Hardy-
Weinberg principle will not favour one genotype over another producing
frequencies expected through application of this law.
The integral relevance for employment of the Hardy-Weinberg principle
is its illustration of expected frequencies where populations are evolving.
Deviation from these projected frequencies indicates evolution of the
species may be occurring. Allele and genotype frequencies are typically
modified per each successive generation and never in ideal Hardy-Weinberg
equilibrium. These modifications may be the result of natural selection,
but (particularly among small populations) may simply result from random
circumstance. They might also arise form immigration of individuals form
other populations where gene frequencies will be unique, or form
individuals who do not randomly choose mates from their wide-ranged
species26.
COMPARISON: LAMARCK vs. DARWIN


Despite the lack of respect lamarckian theory was dealt at the hands
of the early evolution-revolutionaries, the enormous influence it had on
numerous scientists, including Lyell, Darwin and the developers of the
Hardy-Weinberg theory cannot be denied. Jean Lamarck, a French biologist
postulated the theory of an inherent faculty of self-improvement by his
teaching that new organs arise form new needs, that they develop in
proportion to how often they are used and that these acquisitions are
handed down from one generation to the next (conversely disuse of existing
organs leads to their gradual disappearance). He also suggested that non-
living matter was spontaneously created into the less complex organisms who
would evolve over time into organisms of greater and greater complexity.
He published his conclusions in 1802, then later (1909) released an
expanded form entitled Philosophie zoologique. The English public was
first exposed to his findings when Lyell popularized them with his usual
flair for writing, but because the influential Lyell also openly criticized
these findings they were never fully accepted27.
Darwin's own theories were based on those of older evolutionists and
the principle of descent with modification, the principle of direct or
indirect action of the environment on an individual organism, and a
wavering belief in Lamarck's doctrine that new characteristics acquired by
the individual through use or disuse are transferred to its descendants.
Darwin basically built around this theory, adding that variation occurs in
the passage each progressive generation. Lamarck's findings could be
summarized by stating that it is the surrounding environment that has
direct bearing on the evolution of species. Darwin instead contested that
it was inter-species strife "the will to power" or the "survival of the
fittest"28. Certainly Lamarck was looking to the condition of the sexes:
the significantly evolved difference of musculature between male and
females can probably be more easily explained by Lamarckian theory than
Darwinian. There was actually quite a remarkable similarity between the
conclusions of Darwin's grandfather, Erasmus Darwin and Lamarck - Lamarck
himself only mentioned Erasmus in a footnote, and with virtual contempt.
The fact is neither Lamarck nor Darwin ever proposed a means by which
species traits were passed on, although Lamarck is usually recalled as one
of those hopelessly erroneous scientists of past it was merely the basis
for his conclusions that were hopelessly out of depth - the conclusions
were remarkably accurate29.
DARWIN'S INFLUENCES


In 1831 a young Charles Darwin received the scientific opportunity of
lifetime, when he was invited to take charge f the natural history side of
a five year voyage on the H.M.S. Beagle, which was to sail around the world,
particularly to survey the coast of South America. Darwin's reference
material consisted of works of Sir Charles Lyell, a British geologist (he
developed a concept termed uniformitarianism which suggested that
geological phenomena could be explained by prevailing observations of
natural processes operating over a great spans of time - he has been
accused synthesizing the works of others30) who was the author of geologic
texts that were required reading throughout the 19th century including
Principals of Geology, which along with his own findings (observing the a
large land shift resulting from an earthquake), convinced him of geological
uniformitarianism, hypothesizing for example, that earthquakes were
responsible for the formation of mountains. Darwin faithfully maintained
this method of interpreting facts - by seeking explanations of past events
by observing occurrences in present time - throughout his life31. The
lucid writing style of Lyell and straightforward conclusions influence all
of his work. When unearthing remains of extinct animals in Argentina he
noted that their remains more closely resembled those of contemporary South
American mammals than any other animals in the world. He noted "that
existing animals have a close relation in form with extinct species", and
deduced that this would be expected "if the contemporary species had
evolved form South American ancestors" not however, if thereexisted an
ideal biota for each environment. When he arrived on the Galapagos islands
(islands having been formed at about the same time and characteristically
similar), he was surprised to observe unique species to each respective
island, particularly tortoises which possessed sufficiently differentiated
shells to tell them apart. From these observations he concluded that the
tortoises could only have evolved on the islands32.
Thomas Robert Malthus was an English economist and clergyman whose
work An Essay on the Principal of Population led Darwin to a more complete
understanding of density dependent factors and the "struggle in nature".
Malthus noted that there was potential for rapid increase in population
through reproduction - but that food cannot increase as fast as population
can, and therefore eventuality will allow less food per person, the less
able dying out from starvation or sickness. Thus did Malthus identify
population growth as an obstacle to human progress and pedalled abstinence
and late marriage in his wake. For these conclusions he came under fire
from the Enlightment movement which interpreted his works as opposing
social reform33.
Erasmus Darwin, grandfather of Darwin, was an unconventional,
freethinking physician and poet who expressed his ardent preoccupation for
the sciences through poetry. In the poem Zoonomia he initiated the idea
that evolution of an organism results from environmental implementation.
This coupled with a strong influence from the similar conclusions of
Lamarck shaped Darwin's perception on the environment's inherent nature to
mould and shape evolutionary form34.
METHODS OF SCIENTIFIC DEDUCTION

Early scientists, particularly those in the naturalist field derived
most of their conclusions from observed, unproven empirical facts. Without
the means of logically explaining scientific theory, the hypothesis was
incurred - an educated guess to be proven through experimentation. Darwin
developed his theory of natural selection with a viable hypothesis, but
predicted his results merely by observing that which was available.
Following Lyell's teaching, using modern observations to determine what
occurred in the past, Darwin developed theories that "only made sense" -
logical from the point of view of the human mind (meaning it was based on
immediate human perception) but decidedly illogical from a purely
scientific angle. By perusing the works of Malthus did Darwin finally hit
upon his theory of natural selection - not actually questioning these
conclusions because they fit so neatly into his own puzzle. Early
development of logical, analytic scientific theory did not occur until the
advent of philosopher Rene Descartes in the mid-17th century ("I think
therefore I am"35). Natural selection was shown to be sadly lacking where
it could not account for how characteristics were passed down to new
generations36. However, it did present enough evidence for rational
thought to be applied to his theory. Thus scientists were able to develop
fairly accurate conclusions with very limited means of divination.
Opposition from oppressive Judeo-Christian church allowed little room
science. Regardless, natural selection became the basis for all present
forms of evolutionary theory.37
LIMITS TO DARWIN'S THEORY


Darwinism, while comparatively rational and well documented
nevertheless upheld the usual problem that can be found in many logical
scientific conclusions - namely deliberate ignorance of facts which might
modify or completely alter years the conclusions of years of research.
Many biologists were less than convinced with an evolutionary hypothesis
that could not explain the mechanism of inheritance. It was postulated by
others that offspring will tend to have a blend of their two parents
characteristics, the parents having a blend of characteristics from their
ancestors, the ancestors having a blend of characteristics from their
predecessors - allotting the final offspring impure, diminished desirable
c

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