The death god, Mictlantecutli, is often depicted with a skull-like face in pre-Hispanic artefacts.

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However, Dr Reich points out, if humans and chimpanzees had undergone an initial separation at this time, it could account for why the skull has human-like features, including a relatively flat face without a protruding snout.

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All he had discovered was a piece of ape-like skull, a tooth and, some way away, a bit of humanoid femur, which he believed came from the same individual.

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Just like mothers of girls have reacted against the passive princess role, I wish I could see more parents of boys reacting against things like the skull-and-crossbones pirate ghetto.

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Along with the sketches came a cartoon self-portrait of a tall, thin, many-armed young man dipping a pen into his skull, which had sprung open like an inkpot.

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Only later did his measurements show that the skull-cap was from a new transitional species, pithecanthropus erectus, the upright ape-like man.

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With electrodes fixed to his skull, Mr Styffe fixed his mind on game characters, such as a juggler or a Pac-Man-like blob fleeing ghosts in a maze.

ECONOMIST: Monitor