In mechanical systems, devices such as a thermometer, or tachometer (any mechanical measurement device) feed input to a control centre (microchip, thermostat, computer program) and then use its mechanical/electrical outputs to effect the change that it is measuring. As can be seen from both cases, complex systems rely on measurement, comparison and output. It should be noted that such systems oscillate at ideal the ideal performance level, and smart complex systems would utilise smaller effector outputs at premium level to reduce the size of oscillations. .
Complex systems in nature can be seen to evolve from the steady state of macromolecules (Costa, 2002). Billions of years ago modern theory hypothesises that there was no animate object but rather a large collection of atoms. Applying evolution theory on the atomic level it can be derived that molecules were formed from atoms that joined having a steady state. The next step in this process is the idea that these molecules randomly interacting with each other would, at times form larger steady state molecules; macromolecules. Some of these large structures had the ability of keeping steady state when splitting, and then attracting the molecules it needed to reform; duplication. This process, is the modern basis of the modern theory regarding the evolution of life, which in simple terms can be described as the process of prolonging a type of structure through; duplication, reproduction or other processes. .
On the molecular level steady state of a structure is the desired output. In nature, the process which keeps a living creature at its steady state (desired output) is called homeostasis (Campbell, 1993). Living organisms have a very fragile internal environment, which is grossly affected by changes in its external environment. Homeostasis is a complex system which measures numerous types of input; chemical, mechanical, thermal etc.
