 Wolpert’s theoretical approach differed from predecessors in its relation to genetic information. Positional information was proposed as a “universal mechanism” for “translation of genetic information into spatial patterns of differentiation” (Wolpert 1969: 1). The concept was designed to integrate gene-based and organicist approaches to development. Cells “interpret” changes in their positional information, so as to change the pattern of gene activation in a cell. Changing patterns of gene expression drive cell differentiation in a developing organism. This in turn effects spatial distribution of cell forces (e.g., contraction, motility, cell-cell contact), which drives organism-level morphogenesis. However, by 1975, Wolpert’s thinking about development had undergone a conceptual shift (Keller 2002). Between 1971 and 1975, Wolpert’s ideas were “geneticized”, after which he accepted the idea of a genetic program for development and the embryo as “computable” from an egg. In this way, the idea of a morphogen gradient establishing positional information for cells was put under genetic control (see  Section 9).