Apparently the Aztecs liked to display the skulls of vanquished warriors on poles that ran through
|"Dang, these new cars are nice"|
What really seems to surprise scientists about these discoveries is the inclusion of a woman's, dogs, and some horse skulls. This is unique to people who pay attention because Aztecs did not really have horses at their disposal, though they did have dogs, and women.
No one seems a bit surprised that ancient Aztecs were using the subway in Mexico City. Obviously, they had no need for horses with the availability of mass transit. It does add a whole new dimension to the technical sophistication of this advanced society, apart from the skulls on poles that is, and the sacrifices. Times were different then, though.