Scientists announced Thursday they have discovered a new species of human ancestor in a cave in South Africa. Researchers found 15 partial skeletons inside a burial chamber hidden deep in a cave system, the largest single discovery of its kind in Africa. The new species, Homo naledi, appeared to have been capable of ritual behavior and intentionally buried their dead in a remote cave chamber. The discovery was first made in 2013 in a cave called Rising Star in the Cradle of Humankind World Heritage Site, about 30 miles northwest of Jonhannesburg. Researchers are still unsure how long ago these creatures lived, but they are “already practically the best-known fossil member of our lineage,” said Lee Berger, a research professor at the University of the Witwatersrand and a National Geographic explorer-in-residence who led the two expeditions that found and recovered the fossils.