In Human history, evolution is the change in hereditary genetic traits in a population through successive generations. It refers to the process by which an organism goes through genetic changes over a period of time and in reaction to its surroundings. Uninterrupted evolution throughout many generations leads to emergence of new species and varieties. Failure to evolve in reaction to changes in the environment, however, leads to extinction. There is a wealth of evidence pointing to human evolution. This evidence is found in several forms.
Collected human fossils make it possible for researchers to study the changes that took place in the size of the brain and body, diet, movement, and other features of earl y human species during the past 6 million years. Paintings, figurines and stone tools, footprints, and other hints of human activities in the primeval evidence indicate where and how early humans lived and when technological advancements were made. Studies of human genetics illustrate a close relationship between humans and other primates. It shows that we have a connection with all other organisms. Study also indicates the similarities in organisms embryos are evidence of evolution.
The fossil (Ancient Organism Remains) records provide important evidence that evolution took place. Human fossils of more than six thousand individuals varying from teeth to skeletons have been found. Advances in fossils and artifacts dating help to determine the age of remains. With new discoveries being made fast, this remarkable sample means that despite some ancient human species having one or a few fossils representing them, each of the reminders are represented by several fossils. From the fossils it is feasible to study how well an early human species was adapted for; walking upright, for living in hot, tropical habitats or cold, temperate environments.
It is possible to study differences of males and females body sizes. These differences draw a parallel to aspects of social behavior. From fossils also, it is possible to study how fast the children of early human species grew up. Contrary to popular opinion, there was not one line of human species each evolving to the next en route to the modern human being. The humans are a branch of a large and varied family tree. Fossil discoveries point out to the fact that the human family hierarchy has more branches and deeper roots than was thought earlier. There were ages in earlier periods when three or four early human species existed simultaneously, at times in the same place. Homo sapiens are the only surviving species in this previously diverse family.
Genetic data provide key evidence of human evolution. Organisms are similar in varying degrees. Similar organisms have variations that facilitate their adaptation to varying environments. Similarities are clear-cut when one compares organisms that evolved from a common ancestor, and until recent times, comparing physical attributes and behavior was the lone mode of determining the relationship of two or more organisms. Scientists however, can now examine DNA to find out whether organisms are related. Every organism has DNA, which has hereditary information. Scientists compare the DNA of organisms with the more similar the DNA, the more closely related the organisms.
The percentage of genes or DNA shared by organisms reflects their similarities. Organisms share more genes with more closely related organisms. As a result of years of evolution, human beings, classified as primates, exhibit shared genes with all organisms. Besides behavior and anatomy similarities, humans close biological ties with other primate species is evidenced by DNA similarities. Genetic variation between any individual humans is about 0.1%. The chimpanzee DNA compared to humans' indicates a variation averaging about 1.2%. The bonobo (Pan paniscus), closely related to the chimpanzees (Pan troglodytes), varies from humans to equal degree.
The genome variation with gorillas (of the African apes) is roughly 1.6% (Cooper et al. 2003). Interestingly, humans, chimpanzees, and bonobos show matching degree of difference from gorillas. The Asian great ape, the orangutan, is differentiated from humans and the African apes with a variance of approximately 3.1 % (Cooper et al. 2003). Humans and all of the great apes vary from rhesus monkeys in their DNA by about 7 % (Cooper et al. 2003). This shows that humans' closest biological species are chimpanzees and bonobos though humans and these apes did not evolve from any primates existing today. DNA proofs that humans and chimpanzees diverged from the same ancestor species that existed between 6 and 8 million years ago. DNA evidence together with fossils informs this conclusion.
Similarities of Embryos are also a pointer to occurrence of evolution. Embryos of numerous kinds of animals appear largely similar and it is hard to differentiate them. Many characteristics of one kind of organism appear in the embryo of another kind of organism. Fish embryos for instance and human embryos have gill slits. They develop into gills in fish while they disappear before birth in humans. Darwin, (1859) points out that a trace of the law of embryonic similarity occasionally lasts till a late age. This is evidence that organisms are alike and that they develop in a similar manner. It implies that they are linked, share common ancestors and started out the same, progressively evolving to develop different traits.
From the huge amount of proof for biological evolution that is accrued using the above test, we can conclude that evolution took place and still is taking place. Life forms, humans included, evolved from past species, and still keep on evolving. They are not static end-products. What make the topic of evidence of evolution exciting is that finding the meaning of being human entails finding how we became so. The topics gives an insight of how early humans adapted to a dynamic world hence evolving certain characteristics that define human species today.