Discovered within the darkness of Petralona Cave, this remarkable skull - which belongs to an archaic species of human - is notable for the fact that it has a stalagmite growing directly through it. Initially found in 1960 and often referred to as "Petralona Man", this intriguing specimen has long left paleoanthropologist's scratching their heads. A recent study has concluded that it is neither Neanderthal nor human, leaving a question mark over exactly which species of archaic human ancestor it actually belonged to. The 'Petralona Man' skull. Image Credit: CC BY-SA 3.0 NadinaThe skull is also now believed to date...