The explanatory paradigm of biology – the population-genetic, neo-Darwinian Modern Synthesis – which has been established in the middle of the 20th century, has recently been plunged into a crisis. Currently a growing number of biologists call for an expansion of evolutionary theory by a more developmentally orientated account, a so-called ‘Extended Synthesis.’ The novelty of this theory is widely discussed by biologists, historians of science as well as in public. Despite this broad interest in the current dynamics of modern biology, philosophers of science have yet neglected most widely investigating the challenges and problems going along with such a theoretical expansion and integration of conventional and progressive explanatory approaches. Meeting these challenges is the central aim of the proposed research project. Therefore, first, the conceptual foundations and the standards of causal and mechanistic explanation are systematically assessed in those novel fields that are said to drive the current revolutionary change in evolutionary theory, i.e. evolutionary developmental biology (evo-devo), epigenetics, and niche construction theory. Based on this investigation, second, a number of previously neglected inter- and intradisciplinary conflicts are identified, which currently counteract theoretical integration. Subsequently, third, it is analyzed due to which criteria and given which explanatory contexts the more developmentally orientated Extended Synthesis explains better than the neo-Darwinian Modern Synthesis. Thus, this biophilosophical project not only contributes to a better understanding of the current theoretical change in biology. Moreover, it offers solutions that meet the challenges of theoretical integration and explanatory pluralism. In addition, it gives a new impetus to specifying the anthropological relevance of the current expansion of evolutionary theory by explanations that focus on ontogenetic processes and organism-environment interactions.