language family originated in the southwestern United States. Evidence from archaeology and ethnohistory supports the thesis of a southward diffusion across the North American continent, specifically that speakers of early Nahuan languages migrated from Aridoamerica into central Mexico in several waves. But recently, the traditional assessment has been challenged by Jane H. Hill, who proposes instead that the Uto-Aztecan language family originated in central Mexico and spread northwards at a very early date. This hypothesis and the analyses of data that it rests upon have received serious criticism. The proposed migration of speakers of the Proto-Nahuan language into the Mesoamerican region has been placed at sometime around AD 500, towards the end of the Early Classic period in Mesoamerican chronology. Before reaching the Mexican Plateau, pre-Nahuan groups probably spent a period of time in contact with the Corachol languages Cora and Huichol of northwestern Mexico (which are also Uto-Aztecan). The major political and cultural center of Mesoamerica in the Early Classic period was Teotihuacan. The identity of the language(s) spoken by Teotihuacan's founders has long been debated, with the relationship of Nahuatl to Teotihuacan being prominent in that enquiry. While in the 19th and early 20th centuries it was presumed that Teotihuacan had been founded by speakers of Nahuatl, later linguistic and archaeological research tended to disconfirm this view. Instead, the timing of the Nahuatl influx was seen to coincide more closely with Teotihuacan's fall than its rise, and other candidates such as Totonacan identified as more likely. But recently, evidence from Mayan epigraphy of possible Nahuatl loanwords in Mayan languages has been interpreted as demonstrating that other Mesoamerican languages may have been borrowing words from Proto-Nahuan (or its early descendants) significantly earlier than previously thought, bolstering the possibility of a significant Nahuatl presence at Teotihuacan. In Mesoamerica the Mayan, Oto-Manguean and Mixe–Zoque languages had coexisted for millennia. This had given rise to the Mesoamerican language area (language area refers to a set of language traits have become common among the area's languages by diffusion and not by evolution within a set of languages belonging to a common genetic subgrouping). After the Nahuas migrated into the Mesoamerican cultural zone, their language too adopted some of the traits defining the Mesoamerican Linguistic Area. Examples of such adopted traits are the use of relational nouns, the appearance of calques, or loan translations, and a form of possessive construction typical of Mesoamerican languages.