Evolution is the change in the inherited characteristics of biological populations over successive generations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.
We commonly hear natural selection referred to as “survival of the fittest.” This popular phrase has a very specific biological meaning. “Fittest” means that organisms must not only survive to adulthood, they must actually reproduce. If they do not reproduce, their genes are not passed on to the next generation. Evolution occurs only when advantageous genetic variations are passed along and become represented with increasing frequency in succeeding generations.
Darwin provided two key theories that guide much of modern psychological research—natural selection and sexual selection. These theories have great heuristic value, guiding psychologists to classes of adaptive problems linked with survival (e.g., threats from other species such as snakes and spiders; threats from other humans) and reproduction (e.g., mate selection, sexual rivalry, adaptations to ovulation). Advances in modern evolutionary theory heralded by inclusive fitness theory and the “gene’s-eye” perspective guide researchers to phenomena Darwin could not have envisioned, such as inherent and predictable forms of within-family conflict and sexual conflict between males and females.
However, evolution is the binding force of all biological research. It is the unifying theme. In paleontology, evolution gives workers a powerful way to organize the remains of past life and better understand the one history of life. The history of thought about evolution in general and paleontological contributions specifically are often useful to the workers of today. Science, like any iterative process, draws heavily from its history.
The four postulates presented by Darwin in On the Origin of Species by Natural Selection are as follows: 1) Individuals within species are variable. 2) Some of these variations are passed on to offspring. 3) In every generation more offspring are produced than can survive...
The Darwin-Wallace theory of evolution is based on gradualism--the idea that speciation occurs by the gradual accumulation of new traits. This would allow one species to gradually evolve into a different-looking one over many, many generations, which is the scale of evolutionary time.
This theory postulates in the later organisms deviations from the earlier ones; and that these deviations, in so far as they are improvements, perpetuate themselves and become generic marks of differentiation. This, however, imports a difficulty, since the origin of the first of these deviations is inexplicable. The differentia of mankind, whom Darwin, led by the force of analogy, deduces from a species of apes, consists in intellect and moral qualities, but comes into existence only by degrees.
The Galápagos Islands have species found in no other part of the world, though similar ones exist on the west coast of South America. Darwin was struck by the fact that the birds were slightly different from one island to another. He realized that the key to why this difference existed was connected with the fact that the various species live in different kinds of environments.
On returning to England, Darwin and an ornithologist associate identified 13 species of finches that he had collected on the Galápagos Islands. This was puzzling since he knew of only one species of this bird on the mainland of South America, nearly 600 miles to the east, where they had all presumably originated. He observed that the Galápagos species differed from each other in beak size and shape. He also noted that the beak varieties were associated with diets based on different foods. He concluded that when the original South American finches reached the islands, they dispersed to different environments where they had to adapt to different conditions. Over many generations, they changed anatomically in ways that allowed them to get enough food and survive to reproduce. This observation was verified by intensive field research in the last quarter of the 20th century.
The theory of evolution seeks to explain the origin of life on Earth and the origin of different species. Despite the fact that most of the scientific community has regarded it as fact for more than a century, a large number of people still dispute the theory of evolution, and various public controversies have resulted from this disagreement.
Charles Darwin’s insights about evolution have withstood 150 years of scrutiny.
But evolutionary theory has broadened and changed as his ideas have been melded with genetics.
Advances in science have allowed us to gain a better understanding and explaination of evolution. With people like Charles Darwin, we began to look at evolution as a means of explaining life. Genetics teaches us that over time the genome of organisms change. The genetic changes are a result of changes in environment and other factors, which is known as adaptation.