Diatom correlations, isotopic dates (U-series, fission track, and U-Th/He),
stratigraphy, tephra hydration rates, mineral weathering, and vertebrate
suggest that the sediments exposed at the Hueyatlaco archaeological site, as
well as bones from butchered animals found both at Hueyatlaco and at the nearby
El Horno site are at least 250,000 years old".