LamarckismEdit
Lamarckism is the historical label for a family of theories associated with the early 19th-century naturalist Jean-Baptiste Lamarck. At its core, it posited that traits acquired or lost during an organism’s lifetime—through use and disuse, need, or effort—could be transmitted to offspring, thereby shaping the course of evolution without requiring all change to arise from random variation and subsequent selection. This idea stood in deliberate contrast to the later Darwinian framework, which stresses variation that exists in heritable material and differential reproduction as the engine of adaptation. Lamarck’s views emerged into a scientific landscape that did not yet understand genetics, and they influenced how people thought about how organisms adapt to environments in a direct, almost purposeful way.
Over time, the dominant view in biology shifted toward genetic variation and natural selection as the primary drivers of evolution. The lineage of criticism for Lamarckian mechanisms grew as researchers demonstrated a robust germline–somatic separation: what happens in the body during life tends not to be passed on to the next generation in the way Lamarck proposed. August Weismann and others formulated what is sometimes called the Weismann barrier, arguing that hereditary information is largely separated from somatic experience. As a result, the specific mechanism of inheritance Lamarck described was largely set aside in favor of genetic explanations anchored in DNA, mutation, recombination, and selection. August Weismann and Weismann barrier are frequently cited in discussions of the topic.
Nevertheless, the modern scientific landscape preserves some interest in Lamarckian questions, even as it rejects the broad claim that acquired traits are a general source of heritable variation. The discovery of epigenetics opened a contemporary dialogue about non-genetic inheritance: certain marks on DNA or associated proteins can influence gene expression across generations, and parental effects can shape phenotypes in offspring. These findings are linked to epigenetics and transgenerational epigenetic inheritance, and they invite careful nuance rather than a wholesale return to nineteenth-century claims. The consensus remains that genetic information in the germ line is the primary substrate of long-term evolutionary change, with non-genetic inheritance providing context-dependent modifiers rather than a universal mechanism.
History and theory
Origins and core ideas
Lamarck’s influential writings, including the groundbreaking work that began with his studies of organic life, articulated a vision of evolution in which organisms actively respond to their environments through use, disuse, and functional necessity. He argued that organs or features could grow or shrink depending on how often they were employed, and that these acquired changes could be transmitted to offspring, thereby guiding future generations. This perspective offered a dynamic, organism-centered account of adaptation and stood in dialogue with contemporary ideas about the relation between organisms and their environments. For readers who want to trace the lineage of these ideas, see Jean-Baptiste Lamarck and the discussion of inheritance of acquired characteristics.
Mechanisms and evidence
Lamarckism rests on two linked propositions: (1) use and disuse influence the development of an organism’s features; and (2) changes acquired during life can be inherited by subsequent generations. The “acquired characteristics” notion implies a direct, almost teleological link between an organism’s activity and its descendants. In practice, however, this mechanism lacked a robust, empirically supported pathway, and it faced clear objections once genetics emerged as the framework for heredity. For a sense of the historical contrast, see Darwinism and natural selection.
The decline and the Germline idea
The germline–somatic distinction became central to the critique of Lamarckism. The traditional view is that only heritable information coded in germ cells is passed to offspring, and that somatic changes do not reliably propagate across generations. The work surrounding the Weismann barrier contributed to the perception that inheritance is largely genetic, not acquired, and it helped to consolidate the modern synthesis of evolution. For readers exploring the foundations of this shift, see August Weismann.
Neo-Lamarckism and epigenetic echoes
In the 20th century, some scholars revived Lamarckian ideas in a form called Neo-Lamarckism, hoping to reconcile inheritance with environmental responsiveness. While this revival acknowledged that organisms can respond to their environments in meaningful ways, it did not overturn the central role of genetics in heredity. In recent decades, discoveries in epigenetics and related areas have shown that certain non-genetic factors can influence phenotypes across generations in particular contexts, prompting ongoing discussion about how far such mechanisms can contribute to long-term evolution. See also transgenerational epigenetic inheritance for contemporary debates.