Approximately 1500 years since its beginning, around 400 BC, the main city of La Venta started falling apart. Ultimately, the tens of thousands of people who once lived there simply abandoned it. There was some evidence that they purposefully took some of the buildings apart before they left, perhaps to save materials with the intention to rebuild elsewhere. Trade networks stopped flowing. All Olmec style artwork and carvings ended.
As mysterious as the source of the Olmec civilization remains, its disappearance presents just as many questions and ideas. The usual way of a peoples' decline includes being assimilated into another culture or conquered by them completely. From all accounts, however, the Aztec and Maya traded with the late Olmec and did not have serious problems with them.