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
Proto-Mayan language from proto-Mayan to the modern languages are used as the basis of the classification of the Mayan languages. Each sound change may be shared by a number of languages; a grey background indicates no change. The palatalized plosives and are not carried down into any of the modern families. Instead they are reflected differently in different branches allowing a reconstruction of these phonemes as palatalized plosives. In the western branch (Chujean-Q'anjob'alan and Cholan) they are reflected as and . In Mamean they are reflected as and and in Yukatek and K'ichean as and . The Proto-Mayan liquid is reflected as