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Why are humans more closely related to rodents than to snakes?

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A diagram showing the tentative evolutionary relationships among hominid species over the past four million years, with skull images and labeled species names connected by solid and dotted lines to indicate proposed evolutionary pathways. — phylogeny Tentative phylogenetic scheme for the evolution of the human lineage. Solid bars indicate the time ranges during which species are thought to have existed, based on fossil evidence. Dotted lines signify evolutionary relationships between hominin species that have been proposed on the basis of the fossil evidence.

The premise that humans are more closely related to rodents than to snakes is accurate because both humans and rodents are mammals, whereas snakes are reptiles.1

In the context of phylogeny, which maps the branching evolutionary history of organisms, humans and rodents share a more recent common ancestor within the mammalian lineage. Mammals evolved from a group of synapsids known as therapsids during the Triassic Period. This lineage is distinct from the one that gave rise to modern reptiles, including snakes, which are classified as diapsids.12

While humans and rodents have diverged significantly over millions of years, they remain united by shared mammalian characteristics—such as endothermy and specific skeletal structures—that were inherited from their common mammalian ancestor. Snakes, conversely, belong to a separate evolutionary branch that diverged from the lineage leading to mammals long before the emergence of modern mammals.12