transformism

Transformism is an umbrella term used in biology to denote the idea that organisms can change their form over time, giving rise to new species. It stands in contrast to the view that species are fixed and immutable and is associated with pre-Darwinian debates about origins of diversity. The term originated in European natural history and was widely used during the 18th and 19th centuries to describe theories of structural transformation in living beings.

Historical development: Early transformists argued that organisms transform in response to their environments or through internal forces. Jean-Baptiste Lamarck is the most prominent proponent, proposing that traits acquired during an organism’s lifetime could be inherited by offspring, leading to progressive transformation. Other transformists emphasized innate tendencies or life-forces guiding development, rather than random variation alone.

Relation to evolution: When Charles Darwin and Alfred Wallace proposed natural selection as the mechanism of descent with modification, emphasis shifted from transformation by acquired traits to differential reproduction and accumulation of variations. In the early 20th century, some neo-Lamarckian and orthogenetic ideas attempted to integrate inheritance of acquired characteristics with selection, but advances in genetics and population biology gradually favored Darwinian descent with modification as the primary framework.

Modern usage: Today, transformism is largely a historical label in biology. Contemporary evolutionary theory describes common descent with heritable variation and natural selection, underpinned by genetic mechanisms. The term is mainly used in historical summaries of pre-Darwinian and nineteenth-century debates about how organisms change over time.

See also: Evolution, Lamarckism, Natural selection, Common descent.