FREE ESSAY ON EVOLUTION CHARLES DARWIN

EVOLUTION CHARLES DARWIN

EVOLUTION 
TABLE OF CONTENTS Page
INTRODUCTION ............................................... 2
DARWINIAN THEORY OF EVOLUTION .............................. 4
THE THEORY OF BIOLOGICAL EVOLUTION:
CONTRIBUTING ELEMENTS ....................... 7
WALLACE'S CONTRIBUTIONS ................................... 13
HARDY-WEINBERG PRINCIPLE .................................. 15 
COMPARISON: LAMARCK vs. DARWIN ........................... 16 
DARWIN'S INFLUENCES ....................................... 20
METHODS OF SCIENTIFIC DEDUCTION ........................... 23
LIMITS TO DARWIN'S THEORY ................................. 25
MORPHOLOGICAL & BIOLOGICAL CONCEPTS ....................... 27
BIO-EVOLUTION: POPULATION vs. INDIVIDUALS ................ 29
MECHANISMS FOR GENETIC VARIATION .......................... 31
GENETIC VARIATION AND SPECIATION .......................... 35
DARWIN'S FINCHES .......................................... 37
SPECIATION vs. CONVERGENT EVOLUTION ....................... 39
CONCEPT OF ADAPTATION ..................................... 41
PUNCTUATED EQUILIBRIUM ....................................43
VALUE/LIMITATIONS: THE THEORY OF BIOLOGICAL EVOLUTION .... 45
ALTERNATE EXPLANATIONS OF BEING ........................... 47
CONCLUSIONS ............................................... 48
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 find!
ings until he was virtually forced after Alfred Wallace sent him a short paper almos t
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 Da!
rwin'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, gener ally 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 k!
nowledge morals and religion10. 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 - never!
theless it is relatively co mpatible 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 finger s. 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 live!
r. Yet there is a virtual ly 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 or ganisms.
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 speciatio!
n 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 ev ery 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 contrib!
ution to the field: encoura ging 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 thi s 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 wi!
th his usual flair for writ ing, 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
fittest28. 
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 D
arwin'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 faith!
fully 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 cou ld 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 u!
ntil the advent of philosophe r Rene Descartes in the mid-17th century (I think therefore
I am35). 
Natural selection was shown to be sadly lacking where it could not account for how
characteristics were 
passed down to new generations36.