In which way is thinking created in the brain? Until recently it was thought that the brain cortex of mammals such as, e.g., human beings, is a prerequisite for high-level thinking processes. It has now been discovered, however, that even birds without a brain cortex may generate mental performances that are on a level with those of chimpanzees, i.e. jays are able to plan ahead, crows are building complex tools and magpies recognise themselves in mirrors. The latest findings show that although birds do not have a brain cortex, their forebrain consists of brain tissue similar to our brain cortex. Moreover, similar neuro-biological mechanisms can be found in the brains of birds and mammals. Astonishingly enough, most of these similarities are not traceable to a common heritage, they developed in the course of the evolution almost identically both with birds and mammals. Intelligent brains have thus developed several times in the course of the evolution on the basis of quite similar principles.