The terms fact and theory can be applied to evolution, just as they are to gravity.[1] Misuse and misunderstanding of how those terms are applied to evolution have been used to construct arguments disputing the validity of evolution.
In the study of biological species, the facts include fossils and measurements of these fossils. The location of a fossil is an example of a fact (using the scientific meaning of the word fact). In species that rapidly reproduce, for example fruit flies, the process of evolutionary change has been observed in the laboratory.[18] The observation of fruit fly populations changing character is also an example of a fact, using the scientific meaning of the word fact. So evolution is a fact, at least using the scientific meaning of the word fact. These facts require an explanation, just as the observations of gravity did.
In biology, there have been many attempts to explain these observations over the years. Lamarckism, Transmutationism and Orthogenesis were all non-Darwinian theories that attempted to explain the observations of species and fossils and other evidence. However, the Theory of Evolution is the explanation for all relevant observations regarding the development of life, based on a model that explains all the available data and observations. Thus, evolution is not only a fact but also a theory, just as gravity is both a fact and a theory.
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