A trove of life-sized animal rock engravings recently discovered in the Northern Arabian Desert may indicate that the notoriously arid region was populated around 12,000 years ago, contrary to previous beliefs that the area was once uninhabitable. During a survey of three archaeologically unexplored areas in Saudi Arabia’s Nefud Desert — Jebel Arnaan, Jebel Mleiha, and Jebel Misma — researchers found 176 massive petroglyphs carved into sandstone cliffs and boulder facades. Layered in thick, dark rock varnish, the petroglyphs were carved on elevated ledges at heights up to 128 feet. The archaeologists explained that “the difficulty in getting to and engraving these rock surfaces, and their enhanced visibility by height were clearly attractive for the engravers,” who “likely risked their lives to create this art.” A majority of the engravings depicted desert-acclimated animals, including wild camels, ibex, horse-like mammals, and gazelles, save for a few renderings of human figures and...