The shaft tomb tradition is thought to have developed around 300 BCE.Williams, Classic period page and most other sources give the 300 BCE date. For example, Dominique Michelet in The Oxford Encyclopedia of Mesoamerican Cultures says "it probably started earlier" than 200 BCE. Some shaft tombs predate the tradition by more than 1000 years – for example, the shaft tomb at El Opeño in Michoacán has been dated to 1500 BCE but is linked to Central, rather than Western, Mexico. Like much else concerning the tradition, its origins are not well understood, although the valleys around Tequila, Jalisco, which include the archaeological sites of Huitzilapa and Teuchitlan, constitute its "undisputed core".Beekman (2000) p. 388 & 394. The tradition lasted until at least 300 CE although there is not wide agreement on the end date.The proposed end date of the shaft tomb tradition varies considerably. Williams as well as the De Young Museum give a date of 300 CE. The International Council of Museums, on the other hand, provides a date of 500 CE, while the Smithsonian and The Oxford Encyclopedia of Mesoamerican Cultures give 600 CE.
