Ideas aimed at explaining how organisms change, or evolve, over time date dorsum to Anaximander of Miletus, a Greek philosopher who lived in the 500s B.C.Eastward. Noting that human babies are born helpless, Anaximander speculated that humans must have descended from some other blazon of animal whose young could survive without any assistance. He ended that those ancestors must be fish, since fish hatch from eggs and immediately begin living with no help from their parents. From this reasoning, he proposed that all life began in the sea.

Anaximander was correct; humans can indeed trace our ancestry back to fish. His idea, however, was not a theory in the scientific meaning of the word, because it could non exist subjected to testing that might support it or prove information technology wrong. In science, the word "theory" indicates a very high level of certainty. Scientists talk almost evolution equally a theory, for instance, but every bit they talk about Einstein'due south caption of gravity every bit a theory.

A theory is an idea about how something in nature works that has gone through rigorous testing through observations and experiments designed to prove the idea right or wrong. When information technology comes to the evolution of life, various philosophers and scientists, including an eighteenth-century English language doctor named Erasmus Darwin, proposed different aspects of what later on would become evolutionary theory. But development did not reach the condition of beingness a scientific theory until Darwin'south grandson, the more famous Charles Darwin, published his famous book On the Origin of Species. Darwin and a scientific contemporary of his, Alfred Russel Wallace, proposed that evolution occurs because of a phenomenon called natural choice.

In the theory of natural selection, organisms produce more than offspring than are able to survive in their surround. Those that are improve physically equipped to survive, abound to maturity, and reproduce. Those that are lacking in such fettle, on the other hand, either do non accomplish an historic period when they tin reproduce or produce fewer offspring than their counterparts. Natural selection is sometimes summed up as "survival of the fittest" because the "fittest" organisms—those most suited to their surround—are the ones that reproduce most successfully, and are virtually likely to pass on their traits to the next generation.

This means that if an surroundings changes, the traits that enhance survival in that environment volition as well gradually alter, or evolve. Natural selection was such a powerful thought in explaining the evolution of life that it became established as a scientific theory. Biologists have since observed numerous examples of natural selection influencing evolution. Today, it is known to exist but one of several mechanisms by which life evolves. For example, a miracle known as genetic drift can besides cause species to evolve. In genetic migrate, some organisms—purely by adventure—produce more offspring than would be expected. Those organisms are not necessarily the fittest of their species, but information technology is their genes that get passed on to the adjacent generation.

Theory of Evolution

Charles Darwin is more famous than his contemporary Alfred Russel Wallace who also developed the theory of evolution past natural pick.

biologist

Noun

scientist who studies living organisms.

evolution

Noun

change in heritable traits of a population over fourth dimension.

genetic drift

Noun

random variations in the frequencies of genes within populations, particularly minor populations.

hypothesis

Noun

statement or suggestion that explains certain questions about certain facts. A hypothesis is tested to make up one's mind if it is accurate.

Noun

process by which organisms that are better -adapted to their environments produce more offspring to transmit their genetic characteristics.

organism

Noun

living or one time-living affair.

theory

Noun

caption that has not been proven as fact.

  • Credits

    Media Credits

    The audio, illustrations, photos, and videos are credited beneath the media nugget, except for promotional images, which generally link to another folio that contains the media credit. The Rights Holder for media is the person or group credited.

    Director

    Tyson Brownish, National Geographic Order

    Author

    National Geographic Social club

    Production Managers

    Gina Borgia, National Geographic Society
    Jeanna Sullivan, National Geographic Gild

    Program Specialists

    Sarah Appleton, National Geographic Guild
    Margot Willis, National Geographic Society

    Last Updated

    June seven, 2019

  • User Permissions

    For information on user permissions, delight read our Terms of Service. If you lot have questions almost how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you attain out to them, y'all will need the page title, URL, and the appointment you accessed the resources.

    Media

    If a media asset is downloadable, a download push appears in the corner of the media viewer. If no button appears, you lot cannot download or save the media.

    Text

    Text on this page is printable and can be used according to our Terms of Service.

    Interactives

    Any interactives on this folio can only exist played while y'all are visiting our website. You cannot download interactives.