  A fundamental problem in technological studies is how to measure the
evolution of technology. The literature has suggested several approaches to
measuring the level of technology (or state-of-the-art) and changes in
technology. However, the measurement of technological advances and
technological evolution is often a complex and elusive topic in science. The
study here starts by establishing a conceptual framework of technological
evolution based on the theory of technological parasitism, in broad analogy
with biology. Then, the measurement of the evolution of technology is modelled
in terms of morphological changes within complex systems considering the
interaction between a host technology and its subsystems of technology. The
coefficient of evolutionary growth of the model here indicates the grade and
type of the evolutionary route of a technology. This coefficient is quantified
in real instances using historical data of farm tractor, freight locomotive and
electricity generation technology in steam-powered plants and
internal-combustion plants. Overall, then, it seems that the approach here is
appropriate in grasping the typology of evolution of complex systems of
technology and in predicting which technologies are likeliest to evolve
rapidly.
