page_title: Alternatives to evolution by natural selection
section_title: Lamarckism
hierarchical_section_title: Alternatives to evolution by natural selection / Alternative explanations of change / Lamarckism
caption_attribution_description: Portrait of Baron Georges Cuvier, holding a fish fossil Iconographic Collections Keywords: Georges Chretien Dagobert Cuvier; Chollet; Giraud
context_page_description: Alternatives to evolution by natural selection, also described as non-Darwinian mechanisms of evolution, have been proposed by scholars investigating biology since classical times to explain signs of evolution and the relatedness of different groups of living things.
  The alternatives in question do not deny that evolutionary changes over time are the origin of the diversity of life, nor deny that the organisms alive today share a common ancestor from the distant past; rather, they propose alternative mechanisms of evolutionary change over time, arguing against mutations acted on by natural selection as the most important driver of evolutionary change.
  This distinguishes them from certain other kinds of arguments that deny that large scale evolution of any sort has taken place, as in some forms of creationism, which do not propose alternative mechanisms of evolutionary change but instead deny that evolutionary change has taken place at all.
context_section_description: Jean-Baptiste Lamarck's 1809 evolutionary theory, transmutation of species, was based on a progressive (orthogenetic) drive toward greater complexity. Lamarck also shared the belief, common at the time, that characteristics acquired during an organism's life could be inherited by the next generation, producing adaptation to the environment. Such characteristics were caused by the use or disuse of the affected part of the body. This minor component of Lamarck's theory became known, much later, as Lamarckism. Darwin included Effects of the increased Use and Disuse of Parts, as controlled by Natural Selection in On the Origin of Species, giving examples such as large ground feeding birds getting stronger legs through exercise, and weaker wings from not flying until, like the ostrich, they could not fly at all. In the late 19th century, neo-Lamarckism was supported by the German biologist Ernst Haeckel, the American paleontologists Edward Drinker Cope and Alpheus Hyatt, and the American entomologist Alpheus Packard. Butler and Cope believed that this allowed organisms to effectively drive their own evolution. Packard argued that the loss of vision in the blind cave insects he studied was best explained through a Lamarckian process of atrophy through disuse combined with inheritance of acquired characteristics. Meanwhile, the English botanist George Henslow studied how environmental stress affected the development of plants, and he wrote that the variations induced by such environmental factors could largely explain evolution; he did not see the need to demonstrate that such variations could actually be inherited. Critics pointed out that there was no solid evidence for the inheritance of acquired characteristics. Instead, the experimental work of the German biologist August Weismann resulted in the germ plasm theory of inheritance, which Weismann said made the inheritance of acquired characteristics impossible, since the Weismann barrier would prevent any changes that occurred to the body after birth from being inherited by the next generation.
  In modern epigenetics, biologists observe that phenotypes depend on heritable changes to gene expression that do not involve changes to the DNA sequence. These changes can cross generations in plants, animals, and prokaryotes. This is not identical to traditional Lamarckism, as the changes do not last indefinitely and do not affect the germ line and hence the evolution of genes.
caption: Georges Cuvier, shown here with a fossil fish, proposed catastrophism to explain the fossil record.
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