Olmec colossal heads by Matthew Stirling in 1938 spurred the first archaeological investigations of Olmec culture. Seventeen confirmed examples are known from four sites within the Olmec heartland on the Gulf Coast of Mexico. Most colossal heads were sculpted from spherical boulders but two from San Lorenzo Tenochtitlán were re-carved from massive stone thrones. An additional monument, at Takalik Abaj in Guatemala, is a throne that may have been carved from a colossal head. This is the only known example from outside the Olmec heartland. Dating the monuments remains difficult because of the movement of many from their original contexts prior to archaeological
Olmec religion unlike the Mayan "Popol Vuh", or the Aztecs, with their many codices and conquistador accounts. Archaeologists, therefore, have had to rely on other techniques to reconstruct Olmec beliefs, most prominently: The latter two techniques assume that there is a continuity extending from Olmec times through later Mesoamerican cultures to the present day. This assumption is called the Continuity Hypothesis. Using these techniques, researchers have discerned several separate deities or supernaturals embodying the characteristics of various animals. Olmec religious activities were performed by a combination of rulers, full-time priests, and shamans. The rulers seem to have been the most important religious