Findings at the newly excavated Tamtoc archeological site in the north-central state of San Luis Potosi, Mexico, may prompt a rethink of the view that the earliest Mesoamerican peoples were based in the south of Mexico.

A carved stone monolith found at the site, which appears to represent a lunar calendar and contains three human figures and other symbols in relief, may show that the Olmec civilization was more widespread than thought or that another culture thrived alongside it.

Olmec centers have been found in the Gulf Coast states of Veracruz and Tabasco, with only scattered artifacts found elsewhere, but the discovery of this monolith suggests either Olmec penetration far to the north, or of the presence of a new group co-existing with the Olmecs.

Scientists also found evidence at Tamtoc of hydraulic systems, canals and other technology, making it the oldest and most advanced center of its time found in what later became Huasteco Indian region - it is the first and only Huasteco City we know.