Thirteen teeth show two human lineages lived side by side 2.8 million years ago

The line that runs from ape to human was never a line. Thirteen fossil teeth pulled from the Afar region of Ethiopia show that the earliest known members of our own genus, Homo, shared their patch of ground with a second, previously unknown human relative — both alive at the same place between 2.6 and 2.8 million years ago.

That overlap is the finding. For a long time the rise of Homo was pictured as a clean handoff: one ancestor giving way to the next in an orderly march toward us. The teeth from a site called Ledi-Geraru describe something messier and more interesting. Our genus did not step onto an empty stage. It had company.

Some of the teeth belong to early Homo, the same lineage that leads to modern people. The others belong to a species of Australopithecus — the broader group that includes the famous skeleton known as Lucy — but they do not match Lucy’s species or any other on record. They appear to mark a new branch of the human family that has not yet been formally named.

The ages come from the ground itself. The region’s ancient sediments are layered with volcanic ash, and that ash holds crystals of feldspar that act as clocks: by measuring the slow radioactive decay locked inside them, researchers from Arizona State University and their collaborators dated the layers that sandwich the fossils. The teeth were then sorted by the fine details of their shape, the cusps and proportions that separate one hominin from another.

The caution here is built into the evidence. This is a discovery made entirely from teeth — no skulls, no skeletons, nothing yet to show what these creatures looked like or how they may have competed. A new species named from a handful of teeth is a claim that further fossils will have to confirm, and the team itself stops short of giving it a formal name. What the dental anatomy supports is the harder point: more than one kind of hominin was here, together.

That alone reshapes the picture. As many as four hominin lineages may have shared eastern Africa in this window of deep time, which means the traits that eventually defined our genus did not emerge in isolation. They emerged in a crowd, alongside relatives following their own evolutionary experiments — most of which ended.

The Ledi-Geraru project, which first reported these fossils in 2025 and has already yielded the oldest known fossil of the genus Homo, continues to excavate the same sediments. The teeth that named a possible new species are an invitation to keep digging for the jaws and skulls that would turn a strong inference into a face.

Tags: archaeology, human evolution