The curse of the One Rabbit: Tree rings corroborate Aztec folklore

Historical records produced by the Aztecs were pictorial books painted on skins or paper made from bark. The documents included maps, tribute records, genealogies of ruling families, and alteptl annals that mainly recorded the history of individual alteptl (city-states). The annals focused on religious and political events but a variety of natural phenomena were also recorded, such as volcanic eruptions, earthquakes, solar eclipses, storms, and drought.

In the pictorial manuscripts, history is recorded as a continuum of year signs with associated events. Year signs are comprised of a number (1-13) and a day symbol (e.g. rabbit, deer, flint knife). The Aztec calendar is such that particular pairs of numbers and symbols repeat only every 52 years. One of these known as One Rabbit was strongly associated with the occurrence of catastrophic events such as famine.

While the Aztec were recording their history on tree bark, climatic history was also being recorded on tree rings. Many trees grow in annual spurts creating concentric tree rings. The more favourable the weather in a particular year, the thicker the ring. Precise dates can be ascribed to each ring, and thus also to extreme climatic events such as drought.

If we weave the two parallel histories together – the annals and the tree-rings – we can see how the two threads match up. We can see how drought sensed by growing trees translates to droughts recorded by the Aztec. A group of researchers from Mexico and the U.S. did just this (see their article in BAMS). Between 1332 to 1543, thirteen obvious droughts can be identified in the Aztec records. Nine of these had below-average tree growth, the other four were only slightly above the long-term average.

One of the severe droughts led up to the famine of One Rabbit (1454), one of the most widely recorded calamities in Aztec history. The Codex Chimalpopoca reads

"At this time the people were one-rabbited, ... And for three years there was hunger. The corn had stopped growing."

The Codex Telleriano-Remensis depicts images reminiscent of the Dust Bowl. One image has been described as follows:

"three plainly dressed ordinary folk, two males and one female, whose rotating forms and closed eyes depict the fatal effects of yet another disastrous storm. Pictorialized by swirling volutes of dots, the catastrophe this time appears to be caused by gusts of wind or dust."

The account for 1505 recorded in the Codex Telleriano-Remensis depicts scenes of famine, starvation, and death similar to those of 52 years earlier: a weeping fugure and mummy bundle; extreme suffering; famine.

Within Aztec cosmology, the year One Rabbit was strongly associated with catastrophic events such as famine. Tree-ring data suggest their fear was based on long experience. Thirteen of the fourteen One Rabbit years from 882-1558 are covered by available tree-ring data. Ten of these years were immediately preceded by below-normal tree growth, and presumably poor maize yields.

Studying the Aztec’s curse of the One Rabbit shows how multiple lines of evidence, from social accounts and biophysical reconstructions, can be combined to build a more thorough picture of historical events.