<P> This evidence of geographic and demographic centralization leads archaeologists to propose that Olmec society itself was hierarchical, concentrated first at San Lorenzo and then at La Venta, with an elite that was able to use their control over materials such as water and monumental stone to exert command and legitimize their regime . </P> <P> Nonetheless, Olmec society is thought to lack many of the institutions of later civilizations, such as a standing army or priestly caste . And there is no evidence that San Lorenzo or La Venta controlled, even during their heyday, all of the Olmec heartland . There is some doubt, for example, that La Venta controlled even Arroyo Sonso, only some 35 km (22 mi) away . Studies of the Tuxtla Mountain settlements, some 60 km (37 mi) away, indicate that this area was composed of more or less egalitarian communities outside the control of lowland centers . </P> <P> The wide diffusion of Olmec artifacts and "Olmecoid" iconography throughout much of Mesoamerica indicates the existence of extensive long - distance trade networks . Exotic, prestigious and high - value materials such as greenstone and marine shell were moved in significant quantities across large distances . Some of the reasons for trade revolve around the lack of obsidian in the heartland . The Olmec used obsidian in many tools because worked edges were very sharp and durable . Most of the obsidian found has been traced back to Guatemala showing the extensive trade . While the Olmec were not the first in Mesoamerica to organize long - distance exchanges of goods, the Olmec period saw a significant expansion in interregional trade routes, more variety in material goods exchanged and a greater diversity in the sources from which the base materials were obtained . </P> <P> Despite their size and deliberate urban design, which was copied by other centers, San Lorenzo and La Venta were largely ceremonial centers, and the majority of the Olmec lived in villages similar to present - day villages and hamlets in Tabasco and Veracruz . </P>

What was the role of trade in the olmec civilization
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