Referring to the classification system in use by the biological sciences today to classify all living things. It lumps organisms together based on presumed homologies. The assumption is that the more homologies two organisms share, the closer they must be in terms of evolutionary distance. The higher, more inclusive divisions of the Linnaean system are created by including together closely related clusters of the immediately lower divisions. The result is a hierarchical system of classification with the highest category consisting of all living things. The lowest category consists of a single species. Each of the categories above species can have numerous subcategories. The Linnaean system was invented by Carolus Linnaeus in the 18th century.