Nineteenth-century materialists considered life an emergent phenomenon of simple inorganic reactions, a necessary product of the laws of chemistry. Life was thus thought to be a predictable outcome of highly probable reactions. Biological chemistries are known to be elegant and precise in both place and time, parts of highly determined and exactly governed systems of reactions. Nevertheless, the boundary conditions for the reactions are set and controlled by specific chemical constraints. No maneuvering room seems left for an elan vital , a soul, or the body as a whole.
All life is chemically governed chemistry.
In the same fashion, developmental biology increasingly points to the molecule. Bodies unroll from single cells in a pattern dependent on the distribution of chemicals in the cytoplasm of those initial cells. The early molecular patterns set the initial patterns of tissue cells, and in turn, interactive movements of those early tissue layers shape the organs and thus the organism. Morphogenetic movements and cell differentiation are controlled by gradients of inductive chemicals produced by tissues. Some efforts to define the essence of humanity have also looked to biochemistry.