 When the bone is withdrawn, it leaves a very small semicircular flap of flesh which is then pressed down to seal the wound.The wound does not bleed and is almost invisible.In 1884, two such murders were recorded near Adelaide and in the early 1970s a 6,000-year-old skeleton was unearthed at Roonka, a site south of Blanchetown, South Australia, that had a similar bone still in position within the ribcage.