Page "Morphogenesis" Paragraph 3

Some of the earliest ideas on how physical and mathematical processes and constraints affect biological growth, and hence natural patterns such as the spirals of phyllotaxis, were written by D ' Arcy Wentworth Thompson and Alan Turing.

These works postulated the presence of chemical signals and physico-chemical processes such as diffusion, activation, and deactivation in cellular and organismic growth.

The fuller understanding of the mechanisms involved in actual organisms required the discovery of DNA and the development of molecular biology and biochemistry.