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 colossal heads been assigned to the Preclassic period of Mesoamerican chronology, generally to the Early Preclassic (1500–1000 BC), although the two Tres Zapotes heads and the La Cobata Head are attributed to the Middle Preclassic (1000–400 BC). Olmec colossal heads vary in height from and weigh between 6 and 50 tons. All of the Olmec colossal heads depict mature men with flat noses and fleshy cheeks; the eyes tend to be slightly crossed. The general physical characteristics of the heads are of a type that is still common among people in the Olmec region in modern times. The backs of the heads