Final answer:
Linnaeus named primates 'of the first rank' because he saw them as superior mammals due to their complex brains and social structures. He grouped humans with monkeys and apes within the order Primates, based on shared features like opposable thumbs. This classification is part of the Linnaean system which also introduced binomial nomenclature to standardize the naming of species.
Step-by-step explanation:
The term primate was chosen by Carl Linnaeus to designate an order within his taxonomic classification system because he considered primates to be the highest order of mammals, primarily due to their complex brains, varied behaviors, and sophisticated social structures. When Linnaeus developed his taxonomic system, he used physical similarities and differences to group organisms, thereby placing humans along with monkeys and apes in the order Primates. This grouping was due in part to shared anatomical features, such as opposable thumbs, which were beneficial for arboreal life. Linnaeus recognized the superior traits of primates, such as their dexterous hands, large brains, and complex social behavior and thus named them accordingly, as "of the first rank."
His system, known as the Linnaean system of classification, also introduced binomial nomenclature, which provided a standardized way to name all organisms using two Latin names, one for the genus and one for the species, like in Homo sapiens for humans. Over time, other taxonomic ranks were added to create a more nuanced hierarchy, enabling a better understanding of the diversity within and relationships between different species.