Researchers discover 13 million year old fossil of a primeval apes The skull of Nyanzapithecus alesi - a primeval apes living 13 million years ago. © Fred Spoor Read out Spectacular find: In Kenya researchers have discovered the skull of a 13 million year old great ape. The well-preserved fossil is significant in two respects: it closes a gaping gap in the genealogical tree of apes and humans and it is the most complete surviving skull of an extinct great apes, as the paleontologists in the journal Nature report.