Evolution Essay Example

Darwin presented his own theory of evolution, called Darwin's theory, which gained recognition in 1858. Alongside early theories and the synthetic theory, Darwin's widely accepted belief states that all species evolved through natural selection from common ancestors or descendants.

Darwin developed his theory by relying on three main resources: personal observations, Sir Charles Lyell's geological theory from Britain, and Thomas Robert Malthus' population theory from Britain as well. During his time on the H.M.S Beagle from 1831 to 1836, he made numerous observations along the coast of South America where he encountered various plant and animal specimens.

On the Galapagos Islands off the coast of Ecuador, Darwin discovered significant differences between species compared to those found on the mainland.He observed that certain fossils of extinct species closely resembled living species within the same geographic area. In addition, each island had its own distinct form of tortoise, mockingbird, and finch. Despite similarities in structure and eating habits across different islands, there were also notable differences among various forms of these species. Darwin's observations extended beyond variations within individual islands; he also identified dissimilarities between species on one island versus another. Each observation prompted him to question potential connections between separate but similar species.

British economist Thomas Robert Malthus played a crucial role in supporting Darwin's development of the theory of natural selection. Malthus proposed a theory regarding how human populations maintain equilibrium by arguing that food availability for human survival could not keep pace with exponential population growth rates. Factors such as famine, disease, and war significantly impacted population growth dynamics.

In 1838, Darwin utilized Malthus's concept and extended it to plants and animals, ultimately formulating a theory of evolution

through natural selection. Natural selection is the process in which organisms best suited to their environment have a higher chance of reproducing and passing on their traits. Competition arises due to limited resources like food, water, and space.The struggle for survival favors those organisms that have adaptations suited to their environment, allowing them to produce more offspring and leading to the growth of well-adapted species. The concept of "fitness" refers to an organism's reproductive ability and serves as the foundation for the principle of "survival of the fittest." An individual's appearance, body chemistry, physiology, and behavior can all influence their reproductive capability through natural selection. Physiology pertains to how an organism functions. For natural selection to be effective, two biological requirements must be met: firstly, individuals within a population must exhibit variations in inherited characteristics such as height, weight, and eye color; secondly, some of these variations should impact chances of survival and reproduction. Consequently, individuals with higher fitness generally transmit more copies of their genes compared to those with lower fitness. Over time, species evolve genes that enhance survival and reproduction in their specific habitat. There are three types of natural selection: directional selection leads to the emergence of new features that aid a species' adaptation to its environment, resulting in continuous evolution towards more complex traits; stabilizing selection occurs when a species is already well-adapted to its environment; on the other hand, sexual selection plays a role in choosing mates based on specific traits or behaviors.Stabilizing selection, the most common form of natural selection, favors individuals with average characteristics as they have higher reproductive success. Conversely, individuals deviating significantly from the average tend

to have fewer offspring. This phenomenon can be observed in the survival rate of human babies based on birth weight - babies with an average weight have better chances compared to those weighing either more or less than average. Stabilizing selection reduces variation within a population and diminishes complex characteristics.

Sexual selection often falls under stabilizing selection as it involves preferences for certain behaviors or physical traits in mates. It can lead to the development of intricate sexual rituals, like bright coloring attracting potential mates. Birds of different species often display a greater range of color variations in their feathers among males, which is believed to be influenced by sexual selection.

Genetic drift refers to the random alteration of genes within populations resulting from the random assortment of chromosomes received by egg and sperm cells from each parent. The presence of only half of the parent cell's chromosome set in reproductive cells indicates that eggs or sperm carry only half of the parent's genes. Consequently, certain parental genes may not be replicated or passed on to offspring.Genetic drift, a process that leads to random changes in traits over time, can impede a species' ability to adapt to its environment by gradually altering the genetic composition of a population. Evolution can occur through two main mechanisms: natural selection and mutation. Natural selection favors beneficial traits for survival and reproduction, while mutation introduces random variations in the genetic characteristics of a species or population. A population consists of individuals who belong to the same species and inhabit a specific habitat or area. Mutations are changes that occur in genes, which serve as the fundamental units of heredity and have

the capacity to modify inherited traits. Chromosomes are thin structures that contain genetic characteristics and DNA, which carries coded information for hereditary traits. Most animals and plants possess complete sets of paired chromosomes; for instance, human body cells have forty-six chromosomes (or twenty-three pairs). During cell division or reproduction, each offspring inherits half of its chromosomes from each parent. and their contents remain intact while discussing mutations arising from environmental factors like chemicals or radiation that can alter DNA genes and introduce errors during DNA replication in cell division. Modified genes duplicate themselves at the end of cell division, with only mutated genes capable of generating new hereditary traits.Mutations have a vital role in driving evolution and facilitating the development of new species. Unfavorable mutations often lead to traits like albinism, where mutant genes fail to produce normal skin pigment. Animals and plants with albinism face challenges in survival and reproduction compared to those without it. Organisms with mutated genes generally struggle to thrive and reproduce successfully because natural selection eliminates many unfavorable genes; organisms with these genes often do not survive long enough to reproduce. However, certain mutations can be beneficial for organisms as they enable them to better adapt to their environment. For example, plants in dry climates may possess a mutant gene that allows them to develop longer and deeper roots than nearby plants, increasing their chances of survival by accessing more water from the soil. These advantageous mutations significantly contribute to evolutionary change.

The distinctive qualities and characteristics exhibited by Homo sapiens, such as language proficiency, advanced technological skills, and ethical judgment abilities, have long intrigued anthropologists. A recent important discovery

is the close connection between Homo sapiens and African apes. Africa is considered the "cradle of mankind," as Darwin suggested. Darwin also observed that living mammals in each major region are closely related to evolved species from that same region.It is likely that gorilla and chimpanzee-like apes once existed in Africa, making it more probable that our early ancestors resided on the African continent. However, some anthropologists disagreed with Darwin's perspective, stating that Africa was not a suitable environment for the origin of esteemed creatures such as Homo sapiens. In his book The Descent of Man, Darwin concludes that having free hands and a stable stance would have been advantageous for humans' early ancestors to become increasingly upright or bipedal. If hands and arms were constantly used to support the body's weight or primarily designed for climbing trees, they could not have developed the necessary precision for making weapons or accurately throwing stones and spears. Additionally, Darwin suggests a direct link between the evolution of unique locomotion in Homo sapiens and the development of stone weapons, as well as the origin of smaller canine teeth compared to those of apes. Bipedalism led Homo sapiens to develop a more sophisticated and socially interactive mindset which required increased intelligence. As their intellect grew, so did the sophistication and technology of our ancestors. In 1961, Yale University's Elwyn Simons published an important document on Ramapithecus (also known as a primate species), where only parts of an upper jaw were found as remains.Simons observed that the cheek teeth of Ramapithecus, including premolars and molars, resembled those found in humans rather than the pointed ones seen in apes. Additionally, the

canines of Ramapithecus were shorter and less sharp compared to those of apes. By reconstructing the incomplete upper jaw of Ramapithecus, Simons discovered that it had a humanlike shape with an arched roof at the mouth. Similar to humans, Ramapithecus walked upright on two feet, engaged in hunting activities, and lived within a complex social environment.

Considered by many anthropologists as the first hominid species, Darwin's theory of evolution suggests that Ramapithecus is a cultural animal - a primitive version of modern humans that emerged approximately 7 million years ago. Evidence reveals significant differences in blood proteins among humans, chimpanzees, and gorillas. This indicates an evolutionary event occurring 7 million years ago where a common ancestor diverged into three different directions simultaneously. Consequently, this event led not only to the evolution of modern humans but also modern chimpanzees and gorillas.

The debate surrounding Ramapithecus' evolutionary status was settled with the discovery of more complete fossils during the 1980s. While original fossils displayed certain human-like characteristics, they did not represent a fully developed human-like species. Unlike humans who possess U-shaped jaws, Ramapithecus had V-shaped jaws and lived a tree-dwelling lifestyle resembling orangutans.The text discusses several types of primitive Homo sapiens and their characteristics. It states that Phiolethecus, the first primitive ape, shares similarities with modern spider monkeys but has different skull, face, and teeth resembling those of gibbons. Phiolethecus is believed to have used its arms for swinging in trees. Proconsul, previously thought to be a separate genus but now classified as a subgenus of Dryopithecus, is an early African ape considered an ancestor of chimpanzees. Dryopithecus evolved into larger forms that preceded gorillas and was widely distributed

across Europe, India, China, and Africa. Unfortunately, its skeletal structure remains incomplete but has been reconstructed using jaw and tooth fragments. Oreopithecus is a four-foot-tall primate weighing around eighty pounds and is seen as a potential branch in the human family tree. It is considered an ancestor of either apes or monkeys based on its teeth and pelvis. Ramapithecus is recognized as the earliest primate directly preceding modern humans; it is distinguished by its small size and limited number of teeth.Australopithecus Africanus, appearing four million years after Ramapithecus, is the earliest known human ancestor. During this time, there were developments in technology such as the emergence of bipedalism and the creation of tools and weapons made from stone, bone, and wood. Australopithecus Robustus shares a habitat with Australopithecus Africanus in South Africa and has descended from it. Australopithecus Boisei lived in East Africa and was the largest among all australopithecines with larger teeth and jawbones. Unfortunately, this species became extinct.

Advanced Australopithecus stands out from other members of this group due to advanced characteristics and higher levels of intelligence. It is often considered both a true man and referred to as Homo habilis. In comparison to Homo sapiens' cranial capacity, Homo Erectus possessed a smaller and more primitive brain but still lived in social groups while using fire and showing potential for speech.

The Neanderthal Man had a similar cranial capacity to modern humans but made advancements in their way of life such as creating basic clothing and constructing advanced tools. On the other hand, the Cro-Magnon Man is renowned as the first fine artist on Earth. Evidence of their achievements can be seen through cave paintings,

stone engravings, and carved figures. They thrived across all inhabitable regions of the world.
Modern Man has acquired knowledge and evolved from the teachings of the Cro-Magnon. We have gained understanding about cultivating our own food, domesticating animals, exerting control over our environment, and developing cities and civilizations. Despite this progress, we must acknowledge that we act and eat similarly to any other animal. Various theories of evolution support this notion; even Darwin's theory presents evidence that we tend to deny our animalistic nature. Throughout history, our species has undergone astonishing transformations. As we approach the twenty-first century, it remains uncertain what further evolutionary developments await us".