A smattering of ancient rock walls along the river Nile in Sudan appear to represent the oldest known hydraulics system of their kind. New findings suggest people living in the ancient empire of Nubia in northern Sudan were manipulating the river to their advantage as far back as 3,000 years ago. River 'groynes' are rigid structures, laid perpendicular to a shore or bank, that humans still use to this day to manipulate the flow of water and silt. They're highly useful, and farmers and boaters along the Nile have known that for much longer than we ever knew. The Yellow...