Vietnam, with its coastal strip, rugged mountainous interior, and two major deltas, became home to numerous cultures throughout history. Its strategic geographical position in Southeast Asia also made it a crossroads of trade and a focal point of conflict, contributing to its complex and eventful past. The first Ancient East Eurasian hunter-gatherers arrived at least 40,000 years ago. Around 4,000 years ago during the Neolithic period, Ancient Southern East Asian populations, particularly Austroasiatic and Austronesian peoples, began migrating from southern China into Southeast Asia, bringing with them rice-cultivation knowledge, languages, and much of the genetic basis of the modern population of Vietnam. In the first millennium BCE the Đông Sơn culture emerged, based on rice cultivation and focused on the indigenous chiefdoms of Văn Lang and Âu Lạc.