Olmec

The most ancient of the indigenous cultures of Mexico, playing an important role in Mesoamerican Archeology Olmec is a culture of ancient peoples (1300-400 B.C.) of the E Mexico lowlands. A highly developed agricultural society, they left sculptured stone heads weighing over 20 tons. Earthen platforms and pyramidal mounds were common features of their major settlements. The Olmec are often regarded as the mother culture of later Middle American civilizations. The epi-Olmec, the peoples who subsequently inhabited the same lands and were probably descended at least in part from the Olmec, seem to have been the earliest users (from 31 B.C.) of the bar and dot system of recording time. Both the Olmec and epi-Olmec had hieroglyphic writing systems. Source: http://www.encyclopedia.com/articles/09541.html