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Evolution Essay, Research Paper

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

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