The presence of this idea in current books is an illustration of how hard it is to get rid of an idea that does not work. The abundance of marsupials in Australia is more of a problem for evolutionists than a solution. This concept is usually called upon as one of the major controlling factors of evolution. Important factors evolutionists don't often consider. Evolution is a complete contradiction to the second law of thermodynamics.
Evolution demands an ordering of matter from spontaneous generation.
Simple forms of life do not exist. Some are smaller, have fewer parts, yet they carry out all necessary life processes. Mimicry is one organism protecting itself by looking like another organism. Mutualism is two organisms which are interdependent. 600,000,000 years is not enough time for all the necessary transitions.