Short answers, pulled from the story.
The Olmec civilization flourished from roughly 1200 to 400 BC during Mesoamerica's formative period. Their earliest distinct features appeared at San Lorenzo Tenochtitlan around 1400 BC, and the major centers had been abandoned by about 400 BC.
The Olmec heartland was in the Gulf lowlands of what are now the Mexican states of Veracruz and Tabasco. Their major city-temple complexes were at San Lorenzo Tenochtitlan, La Venta, Tres Zapotes, and Laguna de los Cerros.
Olmec derives from the Nahuatl word meaning "rubber people," composed of ōlli (natural rubber) and mēcatl (people). The Aztecs applied this name to their Gulf lowlands neighbors because those people processed rubber from the Castilla elastica tree.
Seventeen colossal heads have been unearthed: ten at San Lorenzo, four at La Venta, two at Tres Zapotes, and one at Rancho La Cobata. They range in height from 1.47 meters to 3.4 meters and are estimated to weigh between 25 and 55 tons each.
The Olmec are strong candidates for originating the Mesoamerican ballgame. A dozen rubber balls dating to 1600 BC or earlier were found at El Manati, a bog 10 km east of San Lorenzo Tenochtitlan, making them among the earliest physical evidence of the game.
Scholars have not determined a definitive cause. The leading hypothesis is that severe environmental changes, including shifts in river courses possibly triggered by tectonic upheaval or agricultural siltation, made the eastern heartland unsuitable for large farming populations between 400 and 350 BC. A competing theory proposes that volcanic eruptions forced population relocation rather than outright extinction.