The human brain has long been considered unique among mammalian brains due to its larger size, overdeveloped cerebral cortex, and high number of neurons. However, recent studies using a novel method to determine the cellular composition of the human brain and other primates, rodents, and insectivores have shown that brain size is not a reliable proxy for the number of neurons. The human brain contains as many neuronal and non-neuronal cells as expected for a primate brain of its size, and the overdeveloped cerebral cortex holds only 19% of all brain neurons, similar to other mammals. The human brain's advantage lies in its economical scaling rules, which allow it to have a larger number of neurons compared to other mammalian brains, particularly rodents, whales, and elephants. These findings suggest that cognitive abilities are better understood through the absolute number of neurons rather than brain size or encephalization. The human brain is a linearly scaled-up primate brain in terms of neuronal numbers, and further research is needed to understand the role of neuroanatomical arrangements and functional changes in human cognition.The human brain has long been considered unique among mammalian brains due to its larger size, overdeveloped cerebral cortex, and high number of neurons. However, recent studies using a novel method to determine the cellular composition of the human brain and other primates, rodents, and insectivores have shown that brain size is not a reliable proxy for the number of neurons. The human brain contains as many neuronal and non-neuronal cells as expected for a primate brain of its size, and the overdeveloped cerebral cortex holds only 19% of all brain neurons, similar to other mammals. The human brain's advantage lies in its economical scaling rules, which allow it to have a larger number of neurons compared to other mammalian brains, particularly rodents, whales, and elephants. These findings suggest that cognitive abilities are better understood through the absolute number of neurons rather than brain size or encephalization. The human brain is a linearly scaled-up primate brain in terms of neuronal numbers, and further research is needed to understand the role of neuroanatomical arrangements and functional changes in human cognition.