Why did von Neumann start using CAs?

• Von Neumann was thinking about the possibility of using a process of evolution as seen in nature to produce successively more complex artificial automata
  
  
• He was also keen to start work on a formal theory of automata, that would contain the general principles common to artificial automata (computers, robots, complex automated systems) and natural systems (cells, organisms, evolution)
  
  
• Originally considered the "kinematic" model
  
  
• Ulam suggested that something like a CA would be more amenable to logical and mathematical treatment