What was the average age of an Aztec emperor?

We’d like to be able to give you an accurate statistical answer but we don’t have all the right data to hand - nor the time to research it! But we can make an educated guess, based on a few key facts we DO know. As there were only eleven emperors in the 150 years from Acamapichtli being crowned in 1375 to Cuauhtemoc being murdered by Spaniards in 1525 - we like to think our guesstimate will be a fair one...

The youngest, without a doubt, was, by all accounts, Chimalpopoca, who was between 9 and 12 when he ascended to the throne. By contrast, we know that Moctezuma II was 34 when he took power in 1502. We also know that Axayactl (sixth huey tlatoani) was the youngest grandson of Moctezuma I, so we can assume he was at most in his early twenties. Further, two younger brothers of Axayacatl - Tizoc and Ahuitzotl - followed him in turn as emperor. This would suggest to us that the average age across the eleven emperors was of the order of 25-26 years old. Whilst that may seem young to us, given that the average life expectancy for an Aztec was only 25 years (see Prof Michael Smith’s answer below), compared to around three times that in the West today, Aztec emperors were clearly pretty mature when they took power.

Image -
scanned from Aztecs edited by Doris Kurella, Martin Berger and Inés de Castro, Linden-Museum Stuttgart, 2021.