In recent years molecular mechanisms and natural strategies have been explored that spontaneously generate genetic variations at low rates without seriously affecting genetic stability at the level of populations. Thereby acquired knowledge suggests systemic aspects of evolutionary interdependences both in the past and in future evolutionary developments. The natural strategy of DNA acquisition by horizontal gene transfer interconnects different branches of the tree of evolution at random times. This makes in principle the entire global gene pool of the biosphere available to any kinds of living beings for their further evolutionary development. The relevance of this knowledge for risk assessments of genetically engineered organisms is discussed.