The data would seem to at least falsify the warfare hypothesis: if they were mostly prisoners-of-war, you'd expect a few localities & demographics to be overrepresented (as they are from the usual enemy city-states, or a burst of young male sacrifices from a victorious battle with many prisoners).
And a gradual dispersion of victims falling off steadily with distance yet with a long tail of very remote origins sounds to me like what you'd get from a mature long-distance network of slave traders.
I think each culture had different customs about choosing sacrificial victims.
For the Aztecs, they conquered most of their neighbors but left a few unconquered — these were the city-states they would engage in annual ritual battle where the highest honor was to capture an enemy warrior. When the Spanish invaded, many of these “over-fished” neighbors became eager allies.
So the “trade” in that case matured to something kind of ugly, a kind of Hunger Games annual harvest of your best warriors. I can imagine wanting some revenge after decades of enduring that from a hegemonic neighbor.
I think the idea that they sacrificed slaves (exclusively?) is a bit overhasty of a conclusion, the Spanish reported that when they "freed" many "victims" waiting to be sacrificed by the Aztecs, they were indignant and demanded to be returned and sacrificed.
A different time, and a different culture, but with a huge amount of similarities too.
Perhaps people viewed it as their sacred duty to be sacrificed?
A related finding - a group (not Mayan, but not quite the Aztecs either) imprisoned an entire Conquistador convoy (Spaniards, Africans, and American Indians) for months and gradually sacrificed and cannibalized them. So the "anyone and everyone" at least in its later incarnations also included unusual foreigners.
The Spanish might be unreliable narrators. Perhaps we cant trust their assessment of situation and even less their reports. They could have been wrong in many ways.
The data would seem to at least falsify the warfare hypothesis: if they were mostly prisoners-of-war, you'd expect a few localities & demographics to be overrepresented (as they are from the usual enemy city-states, or a burst of young male sacrifices from a victorious battle with many prisoners).
And a gradual dispersion of victims falling off steadily with distance yet with a long tail of very remote origins sounds to me like what you'd get from a mature long-distance network of slave traders.