This may be obvious but it is an important point as we will see. Chris Langton is one of the continuing chain of people responsible for major breakthroughs in Alife. Working with Von Nuemann's principles he did much experimentation with Cellular Automata, included Conway's Life. He later went on to produce a simplified reproducing automata that created exact copies of its self. Through his work he began to realise that there was an optimum level of information exchange that was convivial to what we call life.
Life is a complex system, in the dictionary sense of the words.
It is a dynamic equilibrium, that can carry on changing and evolving over a great amount of time without dying out or fading away. It occurred to Langton that this optimum level of information could be measured. Langton created the lambda parameter which was the amount of information being exchanged in a system. By varying this figure in a CA he found that to low a value resulted in things freezing up and too high a value led to chaotic behaviour that made stability very difficult. In the middle was a state, a type of system, which became known as a complex system.