There is an extensive article in Science:
INAH Is continuing to study the skulls uncovered from the Templo Mayor Aztec skull racks (tzompantli) in downtown Mexico City. They have found 180 complete skulls. The victims were defleshed after death and the decapitation technique was clean. They have found that 75% were men, mostly of warrior age, 20% women and 5% children. Often the skulls were decorated and looked like eerie masks. Isotopic analysis of the skulls shows they were born all over Mesoamerica, but spent lots of time in Tenochtitlan before their death. So they were not foreigners. They often spent time with the families of their captors before they were sacrificed. They do display differing dental and cranial modifications. So this will lead researchers to more precise studies of the backgrounds of the sacrificed. New DNA studies will tell us about the genetic diversity of the Mesoamerica population at the time.