Biological Theory’s new issue, 20(3), starts with a “Classics in Biological Theory” article, where Phillip R. Sloan revisits Niels Bohr`s public lecture “Light and Life” delivered in 1932  at the Second International Congress on Light Therapy meeting in Copenhagen. In his address, Bohr discusses the implications of quantum mechanics for biological questions amid the “mechanism-vitalism” debate. This article gives a detailed summary of this historical discussion and the controversies that surrounded Bohr’s arguments and considers the relevance of Bohr’s insights for contemporary discussions of biological reductionism and the place of the human knower in the scientific process.

Luigi Garaffa discusses the role of phenotypic plasticity as an evolutionary factor, analyzing the hypothesis of plasticity-led evolution and the controversies it has generated. The article examines the explanatory range of plasticity-led evolution and mutation-led evolution, and their ability to explain the origin of phenotypic variation, using the North American spadefoot toad as a key example. The author concludes that models based on plasticity-led evolution can be regarded as an autonomous explanans and that the plasticity-led evolution hypothesis could pave the way for a reassessment of the role of development in evolutionary processes.

Michael J. O’Brien, Blai Vidiella, Salva Duran-Nebreda, R. Alexander Bentley, and Sergi Valverde describe how American archaeology has evolved from focusing on reconstructing past cultures through the description and chronological ordering of items found in the archaeological record (culture history) to incorporating evolutionary theory and new methodologies since the 1980s. Accepting the development of a genetics-based theory of cultural transmission and the introduction of phylogenetic methods into anthropology and archaeology enabled the distinction between simple historical continuity and heritable continuity, establishing the concepts of tradition and lineage as key roles in the reconstruction of cultural phylogenies.

Also in the issue, Walter Veit, Samuel J. L. Gascoigne, and Roberto Salguero-Gómez explore the debate over whether organisms evolve towards greater complexity and propose that this can be quantitatively assessed through life history strategies, which reflect the goal-directed nature of living systems. They outline an agenda for future research, focusing on developing mathematical measures of complexity and conducting comparative analyses across species to understand the evolutionary forces influencing changes in teleonomic complexity.

Finally, Enrico Petracca provides a review essay on the book Evolution Evolving by Kevin Lala, Tobias Uller, Nathalie Feiner, Marcus Feldman, and Scott Gilbert. He stresses that the book marks a tipping point in the debate over the “extended evolutionary synthesis” (EES), as it provides a critical mass of arguments and evidence in favor of EES.