"We believe that based on the comparison of archaeological materials that accompanied the human burials," Gamboa told National Geographic News.
In particular, he said, his team discovered some vessels that bore markings "similar to those found in the southern region of the Basin of Mexico."
Two of the children also appear to have been given especially elaborate burials, based on the quality of vessels and other artifacts found nearby, including turquoise that may have originated in the present-day southwestern United States.
Gamboa's discovery requires some important changes to the time line of Mesoamerican history, said Traci Ardren, an archaeologist at University of Miami who was not involved in the research.
"This new discovery at Tula pushes back the evidence for a relationship between child sacrifice and the [appeasement] of the rain god Tlaloc at least 300 years," she said.
Evidence suggests the children sacrificed to Tlaloc were in very poor health when they died and that the sacrifices were not punitive, she added.
Children of "young age and greater purity" were "more powerful mechanisms for the petitions of the living," Ardren said.
Signs of sacrifice are not unique at this time and place, noted Robert Carmack, an anthropologist at the University of Albany, but Gamboa's findings demonstrate the influence that the Toltec had in the region.
"[Cultures during this] period in Central Mexico, especially the Aztecs, were profoundly influenced by the Toltecs, so the existence of Toltec child sacrifice is not at all surprising," he said.
Carmack said early Toltec influence was also pervasive in the highlands of what is now Guatemala, and Maya documents from the region refer to child sacrifice.
"There is sound evidence of the existence of child sacrifice there, although perhaps not on a grand scale," he said.
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