Hundreds of skulls unearthed in Mexico likely point to Aztec human sacrifice

I've read a book or two, and a bunch of random articles/things about north/south America, before the arrival of Europeans. My question is... how do they know this wasn't simply an exercise in "culling" the herd? Many European Cultures did such things(especially the Royalty).

from Pocket http://ift.tt/2tAgvtw