Darwin’sTheory of Evolution
Themost exciting concept of how different species came to existence isthe theory of evolution. This evolution theory was put forward byCharles Darwin in 1859. In his book, the Originof Speciesby natural selection, he states that animals and plants developedthrough a gradual process from their original forms for over millionyears(Wood, 2005).The theory explains that different species went through processes ofmutation, natural selection, and environmental adaptation. CharlesRobert Darwin was one of the scientists who believed that all typesof life forms are related because they descended from a simple commonancestor (Wood,2005).Thus, he went ahead and formulated a theory of natural selection,which explains how an individual’s ability to reproduce, competeand survive determines their existence and changes in a givenenvironment (Wood,2005).
Whena random mutation takes place within the genetic code of a particularorganism, and it survives, the favorable variation is preservedbecause it helps the organism to stay alive. “Thistheory deduces that life developed from non-life the development oflife from non-life and stresses a purely naturalistic ‘descent withmodification’ that creatures evolved from more simplistic ancestorsnaturally over time (Wood,2005).” He went ahead to explain this theory that a change in geneticcomposition in a population occurs because of different reproductivesuccess. The beneficial mutation traits will be passed on to the nextgeneration resulting to an organism that has different features fromtheir ancestor due to gene alteration. He claimed that changes innature take place after a long period, but rapid environmentalchanges can make the modifications to take a lesser period (Wood,2005).
Thistheory was also referred to as “survival of the fittest” byHerbert Spencer when he first read Charles Darwin book on the originof species (Wood,2005).The theory explains how variations in species appear randomly, andthen natural selection occurs, where species with the adaptive traitto the environmental condition survive and reproduce. The offspringof the successful species are more likely to inherit the successfuladaptation traits. This theory explains that inherited traits are thereason as to why we have a change in population sizes andcharacteristics. The population of species highly depends on theirability to survive and reproduce in a particular environment. Themore they reproduce, and the offspring survives, the more they willgive rise to many species that will also influence the population ofthe next generation. If by any chance a particular species withspecific traits an example the individuals with slit eyes reproduceonly two species, then the generation to come will have a lowpopulation density of species with slit eyes. Another example iswhere a member of a particular species develops an advantageoustrait, like wings and thus the species can fly. Then the offspringwill fully inherit this trait and pass it to the next generation. Theother species that do not develop the trait will slowly die andfinally get extinct, leaving only the other kind, which is dominantor there will be two species from similar ancestors with verydistinct features (Wood,2005).
Darwinin one of his research, while voyaging around the world he came tothe Galapagos Islands. He gave evidence of his argument by statingthat the finches of the Galapagos Islands are related to those inSouth America, but have very distinct features from each other. ThisIsland was cut off from South American during the earth landformation and lays about 500 miles away from the mainland (Wood,2005).Darwin argued that this might have been as a result of geographicisolation and subject to different environmental conditions.Anthropologists state that families of mammals called primates werediscovered about 67millon years ago they had grasping hands, complexsocial life, increased brain size, fire and were bipedal. Otherprimates that appeared in the fossil records were like those ofmonkey, apes, and man. Scientists classified species using theircharacteristics, which aided them to group them into families,genera, and species. Human and their ancestors are in the Hominidaefamily. Research shows that African apes are closely related to Homosapiens.
Inthe recent world, we have seen Homosapiensliving in different parts of the world with the diversecharacteristic. As a result of natural selection and the manyprocesses of evolution, human beings have developed various traits asthey settled in different parts of the world due to diverseinterests. Anthropologists found out that there is only one type ofHomosapiens,but they have very different characteristics in skin color, thetexture of their hair, the sizes of their body, blood types, thecolor of the eye, the shape of the eyes and the mouth. According toDarwin theory, different characteristics that people possess, may bedue to selective pressure within a particular environment andisolation. When species are isolated and subjected to differentenvironmental conditions and isolated, they tend to develop traitsthat are favorable for their survival in that niche.
Theinvasion of different diseases all around the globe has become agreat tragedy for the present Homosapiens.Every time a disease breaks out Homosapiensfight for survival through various means. Despite advanced knowledgein these species and presence of modern forms of medication, thetheory of natural selection, where the fittest survive was stillevident. Not every species survived when there was a diseaseoutbreak, but only those that developed a resistant genotype toillness and reacted positively to medication survived. The rest ofthe species increased as their population continued to thrive whilethe rest dwindled in size (Wood,2005).
Anotherdistinct trait that is used to support evolution is the skinpigmentation. According to the theory of natural selection, humanbeings with dark pigmentation have been made to survive and adapt tothe extreme ultraviolet ray, skin cancer and sunburns in theirenvironment. Most of the Homosapiensaround equatorial tropical zones have a dark skin to adapt toincreased sun intensity. As Homosapiensdiverged to different regions all over the world, some species movedto temperate regions where there is less sunlight, and they acquireda lighter skin due to selective pressures, while others moved toareas with intense heat and their gene adapted to those environmentalconditions (Wood,2005).Some obvious traits that are favorable for both the dark and lightskinned are the presence of Vitamins. Those with dark skin have ampleof Vitamin D, which helps in the normal growth of bones since theyare exposed to a lot of ultraviolet radiation compared to the lightskinned. This is another argument on how natural selection favoredthe light and darkened skinned Homosapiensin the temperate and equatorial regions respectively (Wood,2005).
Thegradual changes in species are evident in how the Homosapienshave been changing over the past years. It is claimed thatAustralopithecus was one of the early species of Homosapiensits fossils were found in East and South Africa. They existed 4million years ago and were bipedal. Other species that have beenassociated with the origin of Homosapiensare Homohabilis,who were tool makers. In the later years, other fossils of speciescalled Homoerectus werefound in different parts of the world including Africa, Asia, andEurope (Wood,2005).They had a larger brain associated with technology compared to theother species. These species were associated with the use of fire.Fossil records indicate that about 200,000, years ago, fossils ofhominids called archaic Homosapiens werediscovered (Wood,2005).One of these archaic species was named Neandertal, which issubstantially associated with clothing, religious rituals, fire, andstone tools.
Themodern Homosapienshave been dated to as early as 200,000, years ago. Their technologyhas been referred to as Upper Paleolithic (Wood,2005).Cave paintings and sculptures are highly associated with thisspecies. As they spread throughout the world, the Darwin theory ofevolution by Natural Selection played a role to ensure that theycould adapt and survive in their environment, and helped them indeveloping different physical characteristics (Wood,2005).
Thedevelopment of different traits short, tall, light and dark skinnedwith different eye color and texture and color of the hair that wereadopted in different ages allowed the human species to have distinctgenes over time. These characteristics were as a result of mutationdue to the different environmental conditions of each species. Italso led to variation in population sizes of the various races.
Wood, B. A.(2005). Humanevolution: A very short introduction.New York, NY: Oxford University Press.