Development is a gene’s chosen route to perpetuity. By building and developing phenotypes, genes have been able to exploit uncharted niches that a simple naked replicator could not. An organism’s life history is an evolved solution for inhabiting a niche more successfully than any other competing organism. Niches are not constant, but have opened up through geological time, providing organisms opportunities to infiltrate them. Some niches have become extinct, trapping species and leaving their embalmed remains in the paleontological record. Others have been modified over time, drawing along with them species that have managed to keep up with the changes. At any one point in history, even established, well-functioning niches are not static-they change, as with the seasons. In order to fully exploit a niche, organisms must not only evolve to infiltrate them, but they must change over time within them. Thus, natural selection has created a unique complement of genes for each species whose expression necessarily varies over time. Hence, capsules of inert selfish genes are not the ultimate focus of selection, but developmental patterns of gene expression entrenched in dynamic life cycles. Moreover, organisms do not just track or respond to changes within the environment; they act on niches, altering them and pushing their boundaries as an outcome of their own developmental processes. In this sense, organisms are not solely products of selective forces in the environment; rather, they forge their own niches from the inside out, constrained by characteristics in the physical world in which niches are necessarily embedded. Like balloons self-expanding in confined spaces of different shapes, phylogeny involves the creation of organisms that exist at the boundaries of internal and external pressures. Phylogeny is simultaneously an inside-out and outside-in process of development-and so is ontogeny. If

organisms are conglomerates of adaptive solutions to developmental problems, some of these have been of their own making as they pushed forward the frontiers of their niches.