Scientific activities take place within the structured sets of ideas and assumptions that define a field and its practices. The conceptual framework of evolutionary biology emerged with the Modern Synthesis in the early twentieth century and has since expanded into a highly successful research program to explore the processes of diversification and adaptation. Nonetheless, the ability of that framework satisfactorily to accommodate the rapid advances in developmental biology, genomics and ecology has been questioned. We review some of these arguments, focusing on literatures (evo-devo, developmental plasticity, inclusive inheritance and niche construction) whose implications for evolution can be interpreted in two ways-one that preserves the internal structure of contemporary evolutionary theory and one that points towards an alternative conceptual framework. The latter, which we label the 'extended evolutionary synthesis' (EES), retains the fundaments of evolutionary theory, but differs in its emphasis on the role of constructive processes in development and evolution, and reciprocal portrayals of causation. In the EES, developmental processes, operating through developmental bias, inclusive inheritance and niche construction, share responsibility for the direction and rate of evolution, the origin of character variation and organism-environment complementarity. We spell out the structure, core assumptions and novel predictions of the EES, and show how it can be deployed to stimulate and advance research in those fields that study or use evolutionary biology.

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Evolutionary developmental biology (evo-devo) explores the mechanistic relationships between the processes of individual development and phenotypic change during evolution. Although evo-devo is widely acknowledged to be revolutionizing our understanding of how the development of organisms has evolved, its substantial implications for the theoretical basis of evolution are often overlooked. This essay identifies major theoretical themes of current evo-devo research and highlights how its results take evolutionary theory beyond the boundaries of the Modern Synthesis.

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We describe a new methodology for rapid 2D and 3D computer analysis and visualisation of gene expression and gene product pattern in the context of anatomy and tissue architecture. It is based on episcopic imaging of embryos and tissue samples, as they are physically sectioned, thereby producing inherently aligned digital image series and volume data sets, which immediately permit the generation of 3D computer representations. The technique uses resin as embedding medium, eosin for unspecific tissue staining, and colour reactions (beta-galactosidase/Xgal or BCIP/NBT) for specific labelling of gene activity and mRNA pattern. We tested the potential of the method for producing high-resolution volume data sets of adult human and porcine tissue samples and of specifically and unspecifically stained mouse, chick, quail, frog, and zebrafish embryos. The quality of the episcopic images resembles the quality of digital images of true histological sections with respect to resolution and contrast. Specifically labelled structures can be extracted using simple thresholding algorithms. Thus, the method is capable of quickly and precisely detecting molecular signals simultaneously with anatomical details and tissue architecture. It has no tissue restrictions and can be applied for analysis of human tissue samples as well as for analysis of all developmental stages of embryos of a wide variety of biomedically relevant species.