In 2015, researchers announced a surprising discovery: a completely new species in our own genus, Homo. Homo naledi was discovered not as a few bone fragments or even a single skeleton, but as a huge collection of bones from 14 individuals, all found in the same chamber of a South African cave.

The new species was small in stature and had a brain smaller than any other member of Homo. Some of its features were shared with Australopiths, while a few were all its own. But many other characteristics were shared with other members of Homo, including ourselves. The features on their own suggested Homo naledi might fit in early in our species’ evolutionary history. But, without any dates attached to the bones, any ideas as to where they were largely speculative.

Now the same team that discovered Homo naledi is back with more skeletons from a different chamber in the same cave. With those new skeletons comes some hard dates: only about 250,000 years ago, possibly making H. naledi a contemporary of the earliest modern humans. Those dates upset just about everything we thought we knew about recent human evolution, our genus’ use of tools, and how all those skeletons ended up buried in the cave in the first place.