The Olmecs were a civilization in OTL Mesoamerica. The last Olmec state, Epiolmec, collapsed in 900 CE. The Olmec civilization abandoned its heartland in 400 BCE due to volcanic activity and a changing climate. When the Dark Period began the Olmec city-states were particularly hard hit, losing upwards of half their urban population to disease. Repeated epidemics, notwithstanding, the Olmecs flourished, becoming known to Rome and trading with other cultures in the region. However, the rise of other, more militant civilizations spelled the end of Olmec sovereignty. Remnants of Olmec culture persist in Epiolmec to this day.
The Olmec are credited with the invention of the Mesoamerican writing system.