Other scholars maintain that the largest population group must have been of Otomi ethnicity because the Otomi language is known to have been spoken in the area around Teotihuacan both before and after the Classic period and not during the middle period. Teotihuacan compounds show evidence of being segregated by class, of which three social strata could be distinguished. High elites, intermediate elites, and the laboring class's dwelling spaces differ in ways that are supportive of these class divisions. Residential architectural structures seem to be differentiable by the artistry and complexity of the structure itself. Based on the quality of construction materials and sizes of rooms as well as the quality of assorted objects found in the residency, these dwellings might have been lived in by higher status households. Teotihuacan dwellings that archaeologists deemed of higher standard appear to radiate outwards from the Central district and along the Boulevard of the Dead, although there doesn't appear to be neat zonation into highly homogeneous districts. The laboring classes, which in and of itself was divided, was constituted from farmers and skilled craftsmen to the outer rural population of the city. The inner situated craftspeople of various specialties were housed in complexes of apartments, distributed throughout. These encampments, known as neighborhood centers, show evidence of providing the internal economic backbone for Teotihuacan. Established by the elite to showcase the sumptuary goods that the resident craftsmen provided, the diversity in goods was aided by the heavy concentration of immigrated individuals from different regions of Mesoamerica. Along with archaeological evidence pointing to one of the primary traded items being textiles, craftspeople capitalized on their mastery of painting, building, the performance of music and military training. These neighborhood communities closely resembled individual compounds, often surrounded by physical barriers separating them from the others. In this way, Teotihuacan developed an internal economic competition that fueled productivity and helped create a social structure of its own that differed from the internal, central structure. Aforementioned craftspeople specialized in performing typical actions which in turn left physical evidence in the form of bone abrasions. Based on the wear of teeth archaeologists were able to determine that some bodies worked with fibers with their frontal teeth, insinuating that they were involved with making nets, like those depicted in mural art. Women's skeletons provided evidence that they might have sewn or painted for long periods of time, indicative of the headdresses that were created as well as pottery which was fired and painted. Wear on specific joints indicate the carrying of heavy objects over an extended period of their lives.