Caral is a large settlement in the Supe Valley, near Supe, Barranca province, Peru, some 200 km north of Lima (ca. 10.9° S 77.5° W). Caral was inhabited between roughly 3000 BC and 1600 BC, enclosing an area of 66 hectares. Caral is the oldest known urban center in the Americas, accommodating more than 3,000 inhabitants. Caral is the center of the Caral Supe Civilization, spread over several settlements along the Peruvian coast. A quipu was discovered below the steps to one of the pyramids, dated to an age of roughly 5000 years, fixing the earliest date of this tradition of written communication 2000 years earlier than was previously thought.The Caral pyramids date from as early as the 27th century BC. Construction of the pyramids is thought to have continued until the 21st century BC. Their age is thus comparable to that of the Great Pyramid of Khufu in Egypt, built between 2600 and 2480 BCE.The Caral culture was succeeded by the Chavin culture from ca. 900...