The reconceptualization of the organism as a hierarchy of competing parts under Darwinian selection, advanced by Wilhelm Roux in Der Kampf der Theile im Organismus (1881), is now available in English. Its translation appears at a time when contemporary biology is rediscovering some of its central insights through the study of clonal diversification, tissue dynamics and somatic selection. Roux himself associated the neglect of his book in English-speaking countries with the unenthusiastic review in Nature by George John Romanes, a protégé of Charles Darwin who, although encouraged by Darwin to engage with the work, offered little endorsement. In contrast to prevailing views of the organism as a harmonious unity, Roux framed it as a population of interacting constituents: molecules, cells, tissues and organs, which vary in performance, compete for resources and adapt to changing conditions, paralleling the population-level analysis set forth in On the Origin of Species (1859).
Roux’s argument began with the problem of the apparent purposiveness of body parts, namely their capacity to modify themselves in response to functional demands (think about the training-induced enlargement of muscles, Wolff’s law in bones, vascular remodelling and neuronal plasticity). Whereas Darwin provided a naturalistic explanation of the external purposiveness of species-level adaptation through natural selection, the internal purposiveness of bodily parts remained in need of causal-mechanical elucidation. Roux proposed a solution under the rubric of ‘functional adaptation’, understood as persistent competition among parts, extending down to the molecular level. Within this framework, superior variants were presumed to proliferate and endure, while inferior ones succumbed, thereby biasing composition and form as conditions changed for the organism as a whole.
Roux’s program represented an early attempt to transpose Darwinian struggle into physiology and development. His argument presupposed that modifications acquired during the lifetime were heritable, such that functional improvements generated through intra-organismal competition might accumulate across generations and yield adaptation at the species level. In this way, he sought to link ontogeny and phylogeny, conceiving the training and adjustment of parts within the individual as a mechanism of evolutionary progress. Although this Lamarckian orientation might appear problematic to modern readers, it must be considered in the historical context in which the genetic basis of heredity remained unknown; Darwin and Haeckel both entertained Lamarckian elements alongside natural selection. No account is provided in the book of how such functionally induced modifications could be encoded and transmitted, apart from the appeal to differential maintenance of fitter parts.
Subsequent chapters elaborated examples in which functional stimuli such as load, stretch, tension, innervation or blood flow favoured the survival and persistence of defined sub-parts or cell lineages. Central to this account was the notion of ‘overcompensation’, namely the tendency of tissues to grow stronger than immediately required, indicating that selection was operating not on fixed properties of body parts but on their dynamic responsiveness to stimuli. Roux also rejected the then prevalent theory that increased blood flow alone accounted for activity-induced hypertrophy, arguing instead that tissues actively regulate their nutrition rather than passively absorbing nutrients delivered by circulation. His work culminated in a thesis on the essence of the organic, which he identified with the capacity of parts to adjust morphologically and functionally to altered conditions.
The English edition, prepared by David Haig and Richard Bondi, provides a lucid yet faithful rendering of Roux’s often verbose style, accompanied by an introduction and afterword that situate the text within nineteenth-century debates. Significantly, the translation is of the second edition, which incorporated revisions and responses to critics. This revision was substantial enough to warrant a change of title from Der Kampf der Theile (The Struggle of the Parts) to Der Züchtende Kampf der Theile (Cultivating the Struggle of the Parts). The choice of the later edition represents a historical compromise: although the second edition reflects Roux’s engagement with his critics, the first embodied a more programmatic and untempered formulation of his claims. Readers are therefore presented not only with Roux’s initial programme but also with its early reception history, an aspect that enhances the scholarly value of this volume.
Historically, the work illustrates an early extension of Darwinian theory to intra-organismal physiology and developmental dynamics. It anticipated twentieth-century selectionist frameworks in immunology and neurobiology. It also prefigured later discussions of multi-level selection and the autonomy of cellular lineages within tissues. Philosophically, it posed anew the question of biological individuality by treating component parts as bona fide individuals situated within nested hierarchies of organization and selection (a challenge to the view of somatic cells as fundamentally ‘de-Darwinized’). At the same time, Roux’s account of mechanical and functional forces shaping biological form foreshadowed subsequent debates over structure and function, emphasizing not only that structure conditions function but also that function can reshape structure.
The relevance of Roux’s arguments extends into present-day science, as increasing attention is directed toward somatic evolution in cancer, tissue dynamics and ageing, with significant implications for evolutionary medicine and oncology. Stripped of its Lamarckian elements, Roux’s framework resonates with current evidence that somatic cells vary and undergo clonal selection in tissues, as documented in skin and gastrointestinal epithelium, where competition and Darwinian dynamics continuously operate.
This volume succeeds both as a historical source and as a stimulus for contemporary debate. As a translation, it is faithful, readable and well supported by editorial material. As a historical document, it offers a window into the intellectual climate of late nineteenth-century Darwinism, with all its Lamarckian residues and mechanistic ambitions. As a conceptual resource, it reminds us that the organism can be understood not only as a harmonious whole but also as a collective of competing parts. For these reasons, the book will be of interest not only to specialists in nineteenth-century biology but also to philosophers of biology and practising scientists concerned with clonal dynamics and somatic evolution.
