In his article "On Three Approaches to Tracing Technological Evolution" Y.Karasik explains why TRIZ restricts itself to studying evolution of functions implementation only. Perhaps, there are even more reasons for this restriction. One of them is TRIZ research base.
TRIZ is largely based on analyzing patents. Patents are classified and organized by system function. For legal reasons, patents include “prior art”, i.e. previously known ways to perform similar functions, and compare the new systems against the prototypes. This does not mean that there is any evolutionary relation between a new system and a prototype, but TRIZ often assumes so.
Regardless of why TRIZ restricts itself, if the evolution of systems is not restricted to the evolution of functions implementation, there is no chance to find any general principles and to build any meaningful theory by looking only in this restricted area.
This observation inspired me to apply the old joke to TRIZers. One night a policeman saw a TRIZer looking for something by a light pole. He asked him if he had lost something there. The TRIZer said, "I lost my keys over in the alley." The policeman asked him why he was looking here by the light pole. The TRIZer responded, "The light is here.”
Looking only where “the light is” limits TRIZ to a kind of evolution, which constitutes only an insignificant subset of evolution processes. This was my conclusion in the article "TRIZ and Intelligent Design: a Shared Misconception". Tracing evolution of functions implementation is a mistaken approach for both biological and technological evolutions.
This approach creates leaps and gaps in a picture of biological evolution, and makes organic systems look like their intricate designs have suddenly appeared from nothing. However, in actual biological evolution an organic system usually evolves from other system, which used to perform a function different from the current system’s function. This other system gets gradually modified and on some stage starts to perform the current function. This non-functional approach eliminates the leaps and provides for a consistent picture of evolutionary process.
The functions implementation approach to technological evolution creates leaps and gaps similar to ones it makes when applied to the biological evolution. Using an example of Y.Karasik in his article "How William A. Dembski brings down Darwinism with the help of TRIZ", an aircraft jet engine by this approach should have been evolved from an aircraft propeller engine. This certainly looks like an unbridgeable leap. However, by a non-functional approach, an aircraft jet engine could gradually evolve from some other system, used in a different place and for a different purpose.
A version of such evolution can be found in Bucknell and Wikipedia.
In around 150 BC, Heron created a mechanical force from steam pressure by heating water up in a ball with two opposing bent tubes attached; steam exiting through the tubes created a reaction force that spun the ball.
In 1629, Giovanni Branca invented a turbine for operating a mill, which turned in reaction to a pressurized steam exiting a closed tank through a nozzle.
In 1687, Gravensade attempted the creation of a carriage driven by a pressurized steam exiting a closed tank through a nozzle. This failed because the steam did not produce enough power to move the carriage.
In 1791, John Barber moved away from the pressurized steam and was granted a patent for a system, in which air compressed by a fan is mixed with fuel and burned for jet thrust.
In 1903, Aegidius Elling built a gas turbine, which used an internal rather than external compression.
In 1917, the first patents for jet propulsion were issued. Prior to this the “jet engines” were not used for propulsion but rather for rotating, except maybe for the failed attempt of moving carriage. Still, limitations in design and practical engineering and metallurgy prevented such engines reaching manufacture.
In 1930’s, Frank Whittle and Hans von Ohain independently started work on a jet engine for aircraft. That work proceeded through many modifications in design - hydrogen fuel, gasoline fuel, centrifugal compressor, axial-flow compressor, and others – and the first jet-fighter aircraft was produced in 1944.
In the course of this evolution the systems were used for different purposes and performed different functions. They also were parts of different “super systems”.
The later should be expected. In the living world there are species, which are biologically isolated from each other. This is the reason why in the living world an organic system can evolve only from an organic system of the same organism. There are no isolated “species” among technological systems and thus technological transfer is possible across the entire technical world. Not only an aircraft engine does not have to evolve from another aircraft engine, but it also doesn't have to evolve from another part of aircraft; it can evolve from a part of any other system.
Metaphorically speaking, the entire technical world is one organism. Not only functions implementation approach to technological evolution but any approach considering only evolution of isolated technical systems, is mistaken. Any evolutionary analogy between technical system and organism is flawed. All technical systems are “systems”, “organs” and “tissues” of one technological organism.
A non-functional, inter-system approach to tracing technological evolution should be developed to draw a consistent picture of the evolution without artificial leaps and gaps. It might present technological evolution as a sequence of slight modifications and uncover actual principles that drive this evolution step-by-step. These principles might even provide for effective technological evolution through “level 1” and “level 5” inventions only.