Dev Genes Evol (2011) 221:255–279 ulates that future technological developments will produce such things. Organisms are just highly structured physical systems. The aspect of structure and geometry has, however, been neglected in physical chemistry so far, ‘In structured systems…geometrical and mechanical features may play the dominant role’ (Lotka 1925, 15). ‘The laws of the chemical dynamics of a structured system…will be precisely those laws, or at least a very important section of those laws, which govern the evolution of a system comprising living organisms’ (Lotka 1925, 16). However, how structure arises from less-structured states is not at all addressed by Lotka. All concrete discussion of structural features of cells and organisms and their ontogeny are missing from his book. He jumped directly from chemistry to biology at the population level with some remarks on physiology of the adult organism. Curiously, this jump omitted precisely those parts of biology where a chemically motivated theory was most wanted among biologists. Later, Lotka shifted his mathematical work entirely to population growth and demography and, in 1934, published Analytical Theory of Biological Populations (Lotka 1934). What had happened meanwhile in chemistry? In 1910, Lotka was unaware of any oscillating reaction and in 1920 he mentioned some not well-documented laboratory curi- osities (Lotka 1920a). In 1921, however, William Bray at UC Berkeley published a paper which seemed to describe a reaction of the type Lotka was looking for (Bray 1921). Bray had worked on chemical reactions of hydrogen peroxide. In a solution containing iodate, iodine and hydrogen peroxide, the latter decomposes to oxygen and water. The rate of evolution of oxygen and iodine was found to vary periodically. Bray concludes ‘the writer believes the present example to be the first instance of a periodic reaction in homogeneous solution’ (Bray 1921). With his collaborators, Bray deciphered the basic reaction mechanisms (Bray 1921; Bray and Liebhafsky 1931). However, his work indeed remained a curiosity and most chemists and physicists believed that he had not really described a homogeneous reaction, but that the oscillations were an artefact due to dust particles or gas bubble formation. Theoretical arguments were put forward to show that chemical oscillations are not possible in a homoge- neous phase. Thus, in 1969 a physicochemist could still publish a paper stating: ‘There is no substantiated example of oscillation in a closed homogeneous chemical system and detailed balancing is sufficient to preclude it’ (Swartz 1969). Only in the 1970s was the Bray oscillator reinvesti- gated and was shown to indeed represent a case of an oscillation in a homogeneous phase (Sharma and Noyes 1975; Epstein and Pojman 1998). The generally hostile attitude towards the possibility of oscillating reactions in a homogenous phase also explains 259 why the most famous and best studied case of an oscillating reaction had remained obscure for such a long time (Degn 1972; Winfree 1984). In 1950, the Russian chemist Boris Pavlovich Belousov (1893–1970) tried to find an inorganic version of the citrate cycle of biochemistry. He examined a variety of redox reactions with citrate, oxidating agents and metal ions as catalysts. A combination of citric acid, bromate and ceric ions showed oscillations in the redox state of the ceric ions and travelling waves in unstirred reaction cylinders. The manuscript he submitted in 1951 was rejected with the argument that ‘the supposed discov- ery was impossible’ (Winfree 1984). Belousov spent six more years of work on the system and submitted a revised manuscript which again was rejected. The editor insisted that the paper should be shortened to a letter. At that point, Belousov gave up publishing his work. Only one small abstract remains published in Russian in the proceedings of a conference on radiation biology (Belousov 1959). His original manuscript circulated among colleagues in Moscow, and in 1961, the biophysics student Anatol Zhabotinsky began systematically to analyse the mechanism which later would be called the Belousov–Zhabotinsky (BZ) reaction. Ten papers were published in Russian before experiments were taken up outside Russia and the first paper was published in English (Degn 1967). Meanwhile, an increasing interest in non-equilibrium thermodynamics had emerged within physics. In 1922, Théophile De Donder had introduced the concept of affinity, which provided a connection between irreversible chemical reactions and entropy production (De Donder and van Rysselberghe 1936). In 1931, Lars Onsager had derived his famous reciprocal relations for couple irreversible processes near to equilibrium (Onsager 1931). In 1935, Ilya Prigogine started to study Chemistry and Physics at Brussels and later did his Master and Ph.D. thesis with De Donder. In his autobiography, Prigogine (1977) recalls that as an adolescent he was deeply impressed by Henri Bergson’s L’ evolution creatrice and that at Brussels, the French school of biochemistry and embryology (Brachet, Dalcq and Florkin) influenced his thoughts. By extending De Donder’s approach to other macroscopic irreversible processes including transport phenomena such as diffusion and thermal conduction, Prigogine derived in the mid- 1940s a general expression for entropy production and proved his celebrated theorem of minimum entropy production for non-equilibrium stationary states (Prigogine 1947). The phenomenon of thermodiffusion motivated Prigogine to write his first biological paper. An external temperature gradient applied to a mixture of two gases can lead to a situation in which one of the gases accumulates at the hot, and the other at the cold wall. In this simple case, the exchange of energy with the environment leads to an ordered state within the system and thus to a decrease of