The master thesis addresses the question of evolution of self-consciousness. I propose three hypotheses. The first one states that self-consciousness can be interpreted as a multi-step phenomenon, both in ontogenetical and phylogenetical development. The second hypothesis states that self-consciousness is an adaptation to the requirements of the social environment. The third one states that an organism must be complex enough to be self-conscious. The thesis is theoretical, based on the analysis of selected philosophical and comparative-neuroscientific literature. The philosophical literature sets the basis upon which I interpret the neuroscientific literature. The main idea is that animals and toddlers can be self-conscious, but not in a way as grown humans are. In this way we can talk about different degrees of self-consciousness. The reviewed neuroscientific literature then serves as a basis for determining the probability that an animal is self-conscious. I propose that the more complex behaviors an animal shows, and the more complex nervous system it has, the greater is the probability of its self-consciousness. I conclude that at least great apes, elephants, cetaceans, and maybe corvids, are self-conscious. Other animals are not strictly excluded, since there is a lack of research on this topic.