Perspectives on Integrating Genetic and Physical Explanations of Evolution and Development: An Introduction to the Symposium.

In the 20th century, genetic explanatory approaches became dominant in both developmental and evolutionary biological research. By contrast, physical approaches, which appeal to properties such as mechanical forces, were largely relegated to the margins, despite important advances in modeling. Recently, there have been renewed attempts to find balanced viewpoints that integrate both biological physics and molecular genetics into explanations of developmental and evolutionary phenomena. Here we introduce the 2017 SICB symposium "Physical and Genetic Mechanisms for Evolutionary Novelty" that was dedicated to exploring empirical cases where both biological physics and developmental genetic considerations are crucial. To further contextualize these case studies, we offer two theoretical frameworks for integrating genetic and physical explanations: combining complementary perspectives and comprehensive unification. We conclude by arguing that intentional reflection on conceptual questions about investigation, explanation, and integration is critical to achieving significant empirical and theoretical advances in our understanding of how novel forms originate across the tree of life.