The history of Vietnam is one of the longest continuous histories in the world, with archaeological findings showing human settlements as far back as around half a million years ago and a cultural history of over 20,000 years.[1] Ancient Vietnam was home to some of the world's earliest civilizations and societies - making them one of the world's first people who practiced agriculture.[2][3] The Red River valley formed a natural geographic and economic unit, bounded to the north and west by mountains and jungles, to the east by the sea and to the south by the Red River Delta. The need to have a single authority to prevent floods of the Red River, to cooperate in constructing hydraulic systems, trade exchange, and to fight invaders, led to the creation of the first Vietnamese states in 2879 BC.[4][dead link][clarification needed] The first truly influential part of history in Vietnam occurred during the Bronze Age, when the Đông Sơn culture dramatically advanced the civilization. Vietnam's peculiar geography made it a difficult country to attack, which is why Vietnam under Hùng Vương was for so long an independent and self-contained state. The Âns and Qins were among the earliest foreign aggressors of Vietnam, but the ancient Vietnamese managed to regain control of the country soon after the invasions.