The creature shows a surprising mix of human-like and more primitive characteristics — some experts called it "bizarre" and "weird."

And the discovery presents some key mysteries: How old are the bones? And how did they get into that chamber, reachable only by a complicated pathway that includes squeezing through passages as narrow as about 7½bd} inches (17.8 centimeters)?

The site, about 30 miles northwest of Johannesburg, has yielded some 1,550 specimens since its discovery in 2013. The fossils represent at least 15 individuals.

Researchers named the creature Homo naledi (nah-LEH-dee). That reflects the "Homo" evolutionary group, which includes modern people and our closest extinct relatives, and the word for "star" in a local language. The find was made in the Rising Star cave system.