Such changes in DNA now can be detected and described with great precision. Genetic variations result from changes, or mutations, in the nucleotide sequence of DNA, the molecule that genes are made from. Studies in genetics and molecular biology-fields unknown in Darwin's time-have explained the occurrence of the hereditary variations that are essential to natural selection. As differences accumulate over generations, populations of organisms diverge from their ancestors.Ĭharles Darwin arrived at many of his insights into evolution by studying the variations among species on the Galápagos Islands off the coast of Ecuador.ĭarwin's original hypothesis has undergone extensive modification and expansion, but the central concepts stand firm.
If a particular offspring has traits that give it an advantage in a particular environment, that organism will be more likely to survive and pass on those traits. Furthermore, organisms in nature typically produce more offspring than can survive and reproduce given the constraints of food, space, and other environmental resources.
The term Darwin most often used to refer to biological evolution was "descent with modification," which remains a good brief definition of the process today.ĭarwin proposed that evolution could be explained by the differential survival of organisms following their naturally occurring variation-a process he termed "natural selection." According to this view, the offspring of organisms differ from one another and from their parents in ways that are heritable-that is, they can pass on the differences genetically to their own offspring. The word "evolution" first appeared in the English language in 1647 in a nonbiological connection, and it became widely used in English for all sorts of progressions from simpler beginnings. Many scholars from the ancient Greek philosophers on had inferred that similar species were descended from a common ancestor. This path is best understood as a product of evolution.Ĭontrary to popular opinion, neither the term nor the idea of biological evolution began with Charles Darwin and his foremost work, On the Origin of Species by Means of Natural Selection (1859). Along path leads from the origins of primitive "life," which existed at least 3.5 billion years ago, to the profusion and diversity of life that exists today.
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