Olmec (ōl´mĕk), term denoting the culture of ancient Mexican natives inhabiting the tropical coastal plain of the contemporary states of Veracruz and Tabasco, between 1300 and 400 b.c. The term is also used to refer to contemporaneous groups in highland regions of Mesoamerica (including the states of Oaxaca, Morelos, Guerrero, and the Federal District) who possessed ceramic or sculptural designs similar to those found in the lowlands. The nature of the relationship between the highland and lowland groups remains unclear. The largest and best known Olmec sites are situated along rivers on the coastal plain and include San Lorenzo (1300-900 b.c.) and Tres Zapotes (1000-400 b.c.) in Veracruz, and La Venta (1000-600 b.c.) in Tabasco. At the time of their apogee, these three settlements were probably the most complex "ceremonial" sites found in Mesoamerica. For this reason, the Olmec are often considered to be the cultura madre (mother culture) of later Mesoamerican civilizations. The Olmec were renowned for their sculpting skills and distinctive motifs, leaving numerous carved stelae, as well as freestanding jade and basalt sculptures. Among the more notable examples are numerous sculptured heads of basalt, weighing as much as 40 tons and standing up to 10 ft (3 m) in height. The basalt used for these carvings came from up to 50 mi (80 km) away and was floated to the riverine settlements on rafts. Earthen platforms and pyramidal mounds were also common features of the settlements. The largest single pyramid, found at La Venta, measures 459 ft (140 m) in diameter and 98 ft (30 m) in height. The Olmec economy centered around agricultural production on fertile floodplains, and was supplemented by fishing and shellfishing. By 400 b.c., the distinctive features of Olmec culture disappeared and the region was overshadowed by the emerging central Mexican and Mayan civilizations.