I present here a possible evolution of the brain, from animal brain to human brain. It is very important to specify that the theory is like a tool: it does not support and also does not reject the evolutionist theory. MDT just describes the situation. For any external reality, the brain (human or animal) will make an image- model. This function is basically the same for human and animal brain. In a given external reality many similar elements could exist. For any element, the brain has to make a YM-model. For instance, a dog has to make a YM for any dog which it meets. Such a big number of models use a lot of the brain resources. When there are many similar elements, a solution is to make a concept-YM. Such a YM will fit a big number of similar elements. This reduces the quantity of data to be processed by an animal brain, and so, the brain becomes faster and more efficient. Thus, the first level of evolution of the brain (level 1) is the extensive use of the concept models. This level is, probably, reached by all animals. Observation: the human and animal beings continue to use, for some special situations, pure image models. A pure image model is a YM-model associated with a single entity of the external reality. For instance, a cub has a pure image model of its mother. The first step of the evolution of the brain is based on concept models. A concept model fits an entire class of entities of the external reality. During the interaction, the brain will use a concept model and then, in M-ZM, new properties will be added, or even new elements, if necessary, to understand better and better the external reality. The evolution of the brain continues with level 2. This new facility is based on label-models. As we know, faced with a given external reality, the brain makes an M-ZM model that is able to predict the evolution of the present external reality. Such models are called local-M-ZM. On level 2, it is possible to make a new type of models, which are called label-models. A label- model is able to activate a ZM-model, from the available models of the brain, regardless of the local-M-ZM. Example: an animal senses a specific smell. This can be associated with food or with danger, for instance. In such a situation, the animal can activate a specific ZM-model, which has no direct connection with the local-M-ZM model. This is level 2 of the evolution of the brain. At this level, a special kind of communication between animals occurs. This kind of communication based on label-models is used by human beings as well. It is not precise enough and is also very limited, but useful in many situations, and very fast too. The level 2 is the highest level achieved by the animal brain. The evolution of the brain continues with level 3.