Buried deep underground in a cave whose opening is so narrow special small stature archaeologists had to be recruited to excavate it are thousands of ancient bones from two previously unknown ancestors of modern humans. With small chimp-like heads and very small brains, they resemble apes. But one of two newly-discovered species, Homo naledi, has human-like feet, long legs (for the size of its body), walked upright – and apparently buried its dead, all things similar to humans. Watch the full PBS Nova / National Geographic report, Dawn of Humanity, here now.