THE EVOLUTIONARY GENETICS

Running head: EVOLUTIONARY GENETICS
Evolutionary genetics. "On the origin of species by Charles Darwin
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1EVOLUTIONARY GENETICS
Introduction
Evolution is defined as a process in which the population or species change over time.
The theory of evolution by the natural selection was formulated by Charles Darwin in this
book, “On the Origin of Species” in 1859 (Aldhebiani 2018). Charles Darwin was a British
naturalist who penned this influential yet controversial book. The theory deals with the
process by which the organisms evolve or change over time as a result of the changes that is
heritable like the physical traits and behavioural traits (Aldhebiani 2018). These changes
allow organisms to better adapt to the evolving environment and help them to survive and
reproduce. Alternatively it can be stated that during the course of time, the species evolve and
all the living organisms can trace their descents to a common ancestor. Darwin in this book
also highlighted the overall mechanism of evolution through the theory of Natural Selection.
This theory deals with heritable traits that help organisms or species to survive and to
reproduce and thereby increasing the overall population (Aldhebiani 2018). The following
assignment aims to highlight the main findings of Darwin as highlighted in his book “On the
Origin of Species”. In doing so, the paper will focus on the Theory of Natural Selection,
Survival of the Fittest and genetic drift. At the end, the paper will focus on certain
controversies associated with the Darwin’s theory of evolution and other importance of
Darwin’s theory in showing light towards the concept of gene, its inheritance pattern and
heritability of traits.
Galapagos Finches and Darwin theory
During the course of his survey expedition in South America, Southern trip of Africa
and Australia, Darwin got an opportunity to study local flora and fauna. Over the course of
his expedition, Darwin began to notice intriguing patterns in the distribution and the overall
features of the organisms like finches in the Galapagos islands, in the cost of Ecuador (Grant
and Grant, 2011). Darwin notices that islands in the vicinity of Ecuador had similar yet non-
identical finches. For example, finches that feed on large seeds, tend to have large yet tough
beak. On the other hand, finches those feed on insects have sharp yet pointed beaks. Darwin
also noticed that the Finches that are found in the Galapagos islands are similar to the species
of finches located t the out-skirts of Ecuador in comparison to the finches residing in the
other parts of the world (Grant and Grant, 2011). This change is size or the structure of the
beak depending on the nature o the food is explained by Darwin by the theory of adaptation

2EVOLUTIONARY GENETICS
and this lead to the evolution of the species and speciation further. This observation of the
changing beak size of the Galapagos finches and the concept of adaptation, leads to the
foundation of the Darwin’s book, On the Origin of Species (Grant and Grant, 2011).
Darwin Theory of Natural Selection
Darwin’s theory of Natural selection was proposed in order to explain the mechanism
of evolution. The theory helped in explaining the how the population evolved or undergoes
decent modification and thereby becoming suitable for the environment. Darwin’s concept of
natural selection was based on numerous keys that are based on several observations. The
first observation stated that traits are often heritable (Wright, 2014). Heritability is the
measure of how well the difference in the individuals’ gene account for the differences in
their traits. The second observation of Darwin the theory of Natural Selection include as more
off-springs are produced, in comparison to the capacity of the environment, there occurs
survival of the fittest. The third observation include, the off springs vary in their degree of
heritable traits (colour, size and shape) (Wright, 2014). The differing body size, beak size and
the nature of the feathers of the Galapagos finches are an example of the varying degree of
heritability and thus helping to bring diversity in the species of Galapagos finches. Origin of
whales as explained by Darwin in his theory of Natural selection further helps in the
understanding of the heritability of the genes and how it help in the process of evolution and
speciation (Wright, 2014).
Heritability and Evolution in Humans
Heritability as indicted by Darwin in his first observation is measured from the range
of zero to one. Heritability that is closed to zero, highlights that difference and variation in
traits among the individual is due to the environmental factors and have little influence of
genetic differences (Richards, 2016). Characteristics like different language spoken, religion
and political preferences have zero heritability and they do not have genetic control.
Heritability factor close to one indicates that all variability in the trait comes from the genetic
differences and has negligible contribution of the environmental factors (U.S National
Library of Medicine 2020). The evolution of ear in Homo sapiens is an example of
heritability that leads to the process of adaptations. Mammals like dogs, cats and horse and
swivel their ears towards the direction of the sound. Group of muscles known as auriculares
helps in promotion of ear muscle movements (Richards, 2016). This group mainly include

3EVOLUTIONARY GENETICS
auricularis anterior which help in the upward and forward movements of ear where as
auricularis superior help in downward and backward movement of ear. In humans, wiggling
of ear is regarded as a vestigial feature. This signifies that this feature (moving of ear) was
prevalent in the ancestor of human (Richards, 2016). During, the Stone age, the ancestors of
man used to participate in hunting and thus were required to wiggle their ears towards the
direction of the sound. With gradual evolution, the hunting habits in the human ancestors
reduced gradually and thus flexibility of the ear muscle reduced and gene responsible for the
movements of ear muscles became inactive. This inactive gene failed to get transmitted into
the new lineage (Richards, 2016). This lack of inheritance of the inactive gene during the
process of evolution decreases the capability of the humans to swivel their ears. Thus
providing an example of how heritably helps in the promotion of evolution abased on
adaptation to the changing environment. Based on these simple observations, Darwin
concluded that inside a vast group of population, some of the individuals will express
heritable traits that will help them to survive and reproduce. The off-springs who have
expressed helpful traits will survive and will produce more off-spring in order to carry
forward the legacy. Darwin also concluded that since the helpful traits are heritable, and since
organisms with helpful trait will leave more off-spring these traits tend to become common or
are expressed in the large fractions in the next generation. These helpful traits further help to
being the process of speciation and at the same time, help them to adapt with the changing
environment (Richards, 2016).
Evolution of whales
The theory of evolution under Natural selection was also highlighted by Charles
Darwin in his book, “On the origin of Species”. This theory is further defined as Survival of
fittest. Darwin’s explanation of the theory of evolution through natural selection can further
be explained by the origin of whales. Darwin stated that how the process of natural selection
helps in the transformation of land mammal into whale (Tarizzo, 2012). The transition of
early whales from land to the water bodies mainly occurred through a series of steps that are
predictable (Tarizzo, 2012). Random genetic change like genetic drift and genetic shift
resulted in placing of the nostrils at the further back on the head of land whale. These genetic
drift and shift resulted in increase in the aquatic adaptations in whales as they are now not
required to surface their head to breathe in water. This was followed by more genetic drift
and genetic shift and this result in the evolution of the new species known as water whale