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The evolutionary history of a species is referred to as phylogeny. It's a hypothetical relationship that compares different species groups. It is generally represented as a phylogenetic tree.

Chordates are a group of animals that includes vertebrates like humans. The vertebrates (fishes, amphibians, reptiles, and mammals), cephalochordates (known as amphioxus or lancelets), and tunicates (urochordates) are the three subgroups of living chordates.

A phylogeny is made showing the four lineages cyclostomes, lancelets, gnathostomes, and tunicates. Humans belong to gnathostomes that evolved from a common vertebrate ancestor, as shown in the phylogeny.

Gnathosomes circled in the phylogeny are the only clade whose members have jaws.