Odor-related genes are OR (Olfactory/Odorant Receptor) genes. To date, a total of 900 OR genes have been identified in humans and 1500 in mice; that is, the genes that enable us to smell constitute a family of genes. During the evolution of mammals, some of these genes lost their functions. According to a study conducted by the Anthropogeny Academic Research and Education Center, 60% of humans’ odor-related genes have lost their function, and among the apes, humans have the worst olfactory abilities. 30% of these genes in apes other than humans and 20% in mice have become “pseudogenes” and no longer have a function. Due to the lack of these genes, cells cannot produce the necessary olfactory receptors and the human olfactory repertoire narrows. In the light of these atrophy, it is seen that the human sense of smell is quite blind; however, it can be thought that it still has a good smelling ability according to its habitat. 5-7% of the human brain belongs to the olfactory regions. Although this is an important part, considering that 20-40% of the neocortex is reserved for vision, the smallness of this ratio can be seen. The reason for this is that the ability to smell for the human species is considerably reduced compared to other animals.