Evolution Essay, Research Paper
`We act
like animals, we eat like animals, and we are animals. The many theories of
evolution such as Darwin’s theory of evolution prove to us that we choose to
believe that we are not animals when we really are. Evolution is the sequencial
process of change over periods of time, which shapes and establishes the
formation of modern man.
In referring to evolution, the word means various changes. Evolution refers to
the fabrication and development of life on earth. "Organic evolution"
is the concept that all living beings evolved from simple organisms and have
changed throughout the periods of time to create many and various types of
species. Organic evolution is better known as the "theory of
evolution." There are three main theories of evolution, which are, the
early theories proposed by Comte de Buffon, Baron Cuvier, and Lamarck, the
synthetic theory, and the Darwin theory.
In the 1700s, French naturalists, Comte de Buffon and Baron Cuvier concluded
with the studies of fossils and comparative anatomy that life on earth had
endured many changes through a long period of time. In the early 1800s, another
French naturalist named Lamark, proposed the first complete theory of
evolution. He observed through is observations, depending on the extent to which
the use of the structure, that an animal’s body structure is able to change
during its life span. He also noted that organs and muscles, which were used
often, tended to become larger and stronger. On the contrary, the organs and
muscles, which were used seldom, tended to become smaller and diminish. With
these observations, Lamarck concluded that these characteristics were
hereditary.
Proposed during two decades, the 1930s and 1940s, the synthetic theory involved
a group of scientists. The group of scientists included two American
biologists, Russian Theodosius and German Ernst Mayr, and the British
geneticist and statistician Ronald A. Fisher. Together, they proposed the
synthetic theory which combined Darwin’s theory of natural selection with the ideals
of genetics.
In 1808, French naturalist Chevalier de Lamarck contemplated a theory of
evolution, although, his theory of evolution did not gain any recognition until
1858. In 1858, British naturalist Charles R. Darwin furnished his theory of
evolution, also known as Darwin’s theory. Along with Darwin’s theory of
evolution there early theories and the synthetic theory. In 1858, Charles
Darwin furnished his theory of evolution and the majority of scientists accept
the Darwin theory today. The Darwin theory states that all species evolved from
either many or few common ancestors or descendants under circumstances of
natural selection. Three chief resources aided Darwin to develop his widespread
theory of evolution. One, his personal observations, two, the geological theory
of British scientist Sir Charles Lyell, and three, the population theory of the
British economist Thomas Robert Malthus. Aboard the H.M.S Beagle from 1831 to
1836, Charles Darwin made many of is observations in his quest to propose his theory
of evolution. On the coast of South America, Darwin came under the possession
of many specimens of plants and animals. On the Galapagos Islands, off the
coast of Ecuador Darwin discovered many differences between species on the
islands and with the species on the mainland. For example, Darwin noted that
certain fossils of extinct species were closely similar to living species in
the same geographical area. Darwin also observed that each island possessed its
own form of tortoise, mockingbird, and finch. He also discovered various forms
of these species were closely similar but differed in structure and eating
habits from island to island. In addition, Darwin discovered varieties of
differences between species on one island and another island. With each
observation, Darwin come to the question of possible links between distinct but
similar species.
British economist Thomas Robert Malthus aided Darwin in creating the theory of
natural selection. Malthus proposed how human populations remain in balance. He
debated that any increase in the availability of food for basic human survival
could not equal the geometrical rate of population growth. In addition,
limitations such as famine, disease, or war, play a major role in deciding the
population growth. With this proposal, Darwin quickly applied Malthus’s
proposal in circumstances of plants and animals. In 1838, Darwin designed a
projection of a theory of evolution through natural selection.
Natural selection is a process in which the organisms suited best for their
environment tend to reproduce the most and leave the most descendents. With the
limitation of food for each species, competition is formed in which all livings
beings must compete for the supply of food, water, space, and other resources.
Individual plants and animals whose adaptations of suited best for a certain
environment tend to have an advantage in the competition for survival. Species
with this advantage tend to leave a larger number of offspring than the less
fortunate species. As a result, the size of the species which is best adapted
to its environment increases from generation to generation. The term fitness
refers to the ability of an organism to reproduce. Scientists use this term to
create the concept "survival of the fittest." Natural selection
contains the ability to affect an individual’s ability to reproduce. These
abilities consist of appearance, body chemistry, physiology, and behavior.
Physiology is how an organism functions. In order for natural selection to
function properly, two biological requirements must be encountered. One,
individuals of a population require difference in their hereditary
characteristics. An example of the requirement for difference in their
hereditary characteristics, human beings differ in almost every aspect of their
appearance with include height, weight, and eye-color. In addition, humans also
differ in brain size, thickness of bones, and the amount of fat in their blood.
Secondly, for natural selection to function properly, some of the inherited variations
must affect chances for survival and reproduction. As a result, the fittest
individual tends to pass on more duplications of their genes to their offspring
than the less fittest individuals. In the later periods of time, a species
creates genes that increase its ability to survive and reproduce in its
habitat.
Natural selection consists of three types of selections. One, directional
selection. Two, stabilizing selection. Finally, sexual selection. Direction
selection creates new features that aid a species to adapt to its environment.
Directional selection produces a never ending change in the species toward the
more complex characteristic. Under the circumstance that a species is already
greatly adapted to its environment, stabilizing selection initiates. With
stabilizing selection, individuals with average characteristics produce the
most offspring. On the contrary, individuals that differ the most from the
average tend to produce the least offspring. For example, stabilizing selection
of human beings is the survival rate of human babies according to their birth
weight. On average, when an infants weight is average, the baby tens to survive
better that those who are either heavier or lighter than the average weight. On
the opposite side of directional selection, stabilizing selection gets rid of
complex characteristics, which in turn, decreases the amount of variation in a
population. The most common form of natural selection can most likely be
stabilizing selection. Species who favor mates who display certain types of
behavior or have certain physical features tend to fall under the category of
sexual selection. Complicated sex rituals can be created through sexual
selection. For example, bright coloring can attract a mate. Another example, is
that many males of different species of birds have more variety of colors in
their feathers than females. Genetic drift represents the random change of
genes in populations. Genetic drift is enabled by the random way that egg and
sperm cells receive some chromosomes from each parent. The circumstance that
reproductive cells consist of only half a set of chromosomes as the parent
cell, leads to the conclusion that only half of a parent’s genes are present in
an egg or sperm. As a result, some of the parent genes will not be replicated
and passed on to its offspring. In addition, genetic drift does not allow
species to evolve to accommodate to their environment. The cause of this
incapability occurs because genetic drift causes random changes in the cycle of
characteristics. Over a long period of time, genetic drift is able to gradually
alter the genetic features of a population.
As time goes on, evolution can change in two distinct manners. Evolution can be
altered through the most common aspect of natural selection. On the contrary,
evolution can also be altered through mutation. Mutation outputs random
differences in the genetic features of a species or a population. A population
is an accumulation of individuals, which are of the same species and live in
the same habitat or area. Mutation is an altered gene. A gene is the basic and
main unit of hereditary. Inherited characteristics of an organism is altered
from mutations.
Chromosomes are threadlike structures, which transport hereditary
characteristics. DNA, the coded information that determines hereditary
characteristics, is carried in large numbers by chromosomes. The majority of
animals and plants contain a full set of paired chromosomes. Human body cells,
for instance, have forty-six chromosomes, or twenty-three pair. During cell
division or reproduction, each offspring receives half the set of chromosomes
from each parent. Mutations can most likely be caused by environmental factors,
with factors such as chemicals or radiation. Chemicals and radiation alter DNA
genes and even create errors during the replication of DNA during cell
division. Nearing the end of cell division, the gene has changed and duplicates
itself in the altered form. Only a mutated gene can introduce new hereditary
characteristics. Mutations are not only the building blocks of evolutionary
change, but also, are the building blocks of the development of new species.
The majority of mutations tend to create adverse traits, such as, albinism.
Albinism is a mutation that contains mutant genes, which lack the ability to
generate normal skin pigment. Animals and plants, which contain the albinism
gene, are unable to survive and reproduce as much and as well as the animals
and plants without the albinism gene. Thus stating, that organisms with a mutant
gene, will be unable to survive and reproduce as well as the organisms without
a mutant gene. On the contrary, many unfavorable genes are eliminated by
natural selection because most of the organisms containing the unfavorable
genes will die before they are able to reproduce. On the other hand, some
mutations benefit organisms in adapting better to their existing environment.
For example, a plant in a dry climate may contain a mutant gene, which enables
its roots to grow longer and deeper that its surrounding plants. As a result,
the plant has a better chance for survival and more reproduction because its
roots are able to extend deeper into the soil and collect water. The favorable
mutations create the aspects for evolutionary change.
The distinct qualities and features of the Homo sapiens have appalled
anthropologists. Examples of these special qualities and features of the Homo
sapiens, which have appalled anthropologists, are features such as language,
high technological skills, and the ability to make ethical judgements. Despite
these qualities, the most significant and most recent quality, is the Homo
sapiens connection with the African apes is practically the same.
"The cradle of mankind…," as Darwin said,"…was Africa."
Darwin also stated ," In each great region of the world, the living
mammals are closely related to the evolved species of the same region. It is,
therefore, probable that Africa was formerly inhabited by extinct apes closely
allied to the gorilla and chimpanzee: and as these two species are now man’s
nearest allies, it is somewhat more probable that our early progenitors lived
on the African continent than elsewhere."
On the contrary, many anthropologists disagreed with Darwin’s opinion because
the Dark Continent, better known as Africa, was not a fit enough place for the
origin of a so noble of a creature as the Homo sapiens. Another conclusion made
by Darwin was this:
" If it be an advantage to man to have his hands and arms free and to
stand firmly on his feet,…then I can see no reason why it should not have
been more advantageous tot he progenitors of man to have become more and more
erect or bipedal. The hands and arms could hardly have become perfect enough to
have manufactured weapons, or to have hurled stones and spears with true aim,
as long as they were habitually used for supporting the whole weight of the
body…or so long as they were especially fitted for climbing trees."
This was written by Darwin in his book called The Descent of Man. The Descent
of Man was written to distinguish the evolvement of humans, bipedalism,
technology, and an enlarged brain. In this quote, Darwin is stating that the
evolution of the Homo sapiens unusual form of locomotion was directly linked to
the production of stone weapons. Furthermore, Darwin linked these evolutionary
changes to the origin of the canine teeth in humans. In addition, the canine
teeth of a human are unusually small compared to the canines of apes.
As bipedal creatures, Homo sapiens developed a more intense and interactive
social mind-frame. With the development of a more intense and interactive
social mind-frame, Homo sapiens required more intellect or mentality. As the
intelligence of our ancestors, Homo sapiens, increased, the greater was their
sophistication and technology.
In 1961, Elwyn Simons, at Yale University, published a monumental document,
which stated that a small apelike creature named Ramapithecus, which was the
first known hominid species. Hominid is also known as a primate. Parts of an
upper jaw were the only remains of Ramapithecus. He discovered that the cheek
teeth, which consist of the premolars and molars, are similar to the human
cheek teeth. The cheek teeth of Ramapithecus were flat and not pointed as ape
teeth are. In addition, Simons discovered that the canines were shorter and
blunter than the canines of apes. Yet another discovery Simons came to was that
the reconstruction of the incomplete upper jaw of Ramapithecus showed a
humanlike shape. The upper jaw of Ramapithecus, is an arch at the roof of the
mouth. Similar to humans, Ramapithecus walked upright on two feet, hunted, and
lived in a complex social environment. With the aid of Darwin’s theory of
evolution, Ramapithecus, the very first hominid species, became viewed by many
anthropologists has a cultural animal, which states that Ramapithecus is a
primitive version of modern humans.
The first human species is believed to have evolved only about 7 illion years
ago. Data indicated that the blood proteins of humans, chimpanzees, and
gorillas are equally different from each other. In other words, a type of
evolutionary event 7million years ago caused a common ancsestor to split in
three directions at once. This type of evolutionary event not only led to the
evolution of modern humans but also of modern chimpanzees and modern gorillas.
In the 1980s, discoveries of much more complete specimens of Ramapithecus
fossils, settled the dispute of the evolutionary event.
The original Ramapithecus fossils are undisputedly human like in various ways,
but the species of Ramapithecus was not human like. The jaw of Ramapithecus was
a V-shape, not a U-shape. In addition, Ramapithecus had lived a lifestyle in
trees, similar to its ancestors, the orangutans. Also Ramapithecus was not a
bipedal ape, which proved that it was less of a primitive hunter-gatherer.
The beginning of the apes and forward onto the human proceeds through fourteen
different types of primitive Homo sapiens. The first primitive ape,
Phiolethecus is similar to a modern-day spider monkey except for its skull,