15. The Olmecs were the first Mesoamerican civilization before they suddenly vanished in the 4th century BCE
The Olmec were the first known major civilization in Mesoamerica, located predominantly in the Gulf lowlands and inhabiting this area from 1400-400 BCE. Emerging as a distinct culture at some point between 1400-1200 BCE, the founding of the Olmec city of San Lorenzo Tenochtitlán, not to be confused with the Aztec city of Tenochtitlán, during this time is often considered the formal beginning of the fledgling civilization; aided by rich soil and the transportation opportunities afforded by the Coatzacoalcos River Basin, the Olmecs flourished in a manner comparable to other ancient civilizations residing on the banks of the Nile or Indus.
Atypically for an ancient civilization, this agricultural productivity enabled densely concentrated populations in large cities, with Tenochtitlán believed to have housed a population in excess of 10,000; this, in turn, created sufficient demand for artistic culture, resulting in the creation of the luxury objects which define the Olmec civilization today. Notable among these cultural artifacts, the Olmecs fashioned masks of jade, believed to have been used as symbols of status by the ruling classes, and carved colossal heads from single blocks of volcanic basalt; in total 17 such heads have been discovered, with the largest 11 feet in height and weighing 55 tons. The purposes of these heads, the characteristic image of the Olmec civilization, remains unclear, with the accepted theory that they represent great rulers and perhaps even were believed to capture the souls or emotions of these acclaimed individuals.
Like the Maya after them, it is unknown why the Olmec civilization suddenly entered into a period of rapid decline; this decline occurred in two stages. Beginning in around 950-900 BCE, the great city of Tenochtitlán was abandoned by the Olmec and much of its culture lost; it is believed internal conflict or changing environmental conditions might have contributed to the abandonment of the greatest city in the region. The remaining Olmec population relocated to La Venta, home to the largest Mesoamerican structure of its time – “The Great Pyramid” – until when between 400 and 350 BC the population of the eastern half of Olmec territory dramatically depopulated. Archeologists have speculated this depopulation was the product of “very serious environmental changes that rendered the region unsuited for large groups of farmers”; among the possible variables capable of creating such a seismic shift in environment, it has been suggested tectonic activity, the silting up of rivers, or volcanic eruptions.