neoLamarckism

Neo-Lamarckism refers to a family of evolutionary theories that emerged in the late nineteenth and early twentieth centuries, aimed at reviving and revising Lamarck's concept of inheritance of acquired characteristics within the Darwinian framework. Proponents argued that traits acquired during an organism’s lifetime—due to use or disuse, environment, or behavioral modification—could be transmitted to offspring, thereby enabling lineages to adapt directly to changing conditions. The field was heterogeneous, proposing mechanisms ranging from germline changes and cytoplasmic inheritance to environmental conditioning of developing embryos.

Neo-Lamarckism coexisted with Mendelian genetics and natural selection, and it was one of several challenges to a strictly gene-centered view of evolution before the Modern Synthesis clarified the primacy of genetic inheritance and population-level processes. In the early to mid-twentieth century, the approach fell out of favor as genetic and evolutionary theory solidified.

A notable figure associated with neo-Lamarckian ideas is Paul Kammerer, whose experiments with midwife toads were popular at the time but later subjected to criticism and discredited on methodological grounds. Despite the decline of neo-Lamarckism as a general theory, the term remains in historical discussions of evolution.

In contemporary biology, epigenetics has shown that some environmentally induced changes in gene expression can be inherited for a few generations in certain species. These observations do not provide a general mechanism for the inheritance of acquired traits or long-term evolution, but they do illustrate how heritable variation can be influenced by the environment. Neo-Lamarckism, therefore, is regarded largely as a historical category rather than a valid framework for evolution.