In northwestern Saudi Arabia, a hunter surrounded by a pack of dogs threads an arrow, props it up against the string of his bow, and pulls it back to kill a wild animal roaming nearby. He's flanked by other hunters readying their weapons.

This scene, and others like it, are engraved onto the cliffsides protruding from the dry, arid desert covering the northern region of present-day Saudi Arabia. A team of researchers think it may be the earliest depiction of dogs ever documented—although other experts aren't yet convinced of that fact. (This story was first reported by David Grimm for Science.)

"The distinction of herders and hunters was immediately clear," said Maria Guagnin, an archaeologist from the Max Planck Institute