Just about two years ago, Patricia Crown published the first study to identify residues of theobromine — a distinctive chemical present in the cacao plant, and hence in chocolate drinks — north of Mexico.
The residues were recovered from three of five tested sherds, pieces of three painted cylinders from Pueblo Bonito in Chaco Canyon, and dated to A.D. 1000–1125. Because of the location where they were found, and the unusual nature of the pots, it seemed likely that chocolate drinking was an exclusive practice of a small specialized group, something distinctive of rituals.
Fast forward to the forthcoming edition of the Journal of Archaeological Science, and an article by Dorothy Washburn of the University Museum at the University of Pennsylvania.
Washburn and her colleagues have taken the next logical step: they tested a wider range of pots from the US Southwest Pueblos.
To quote the abstract of their paper in press, they found theobromine in
non-local vessel forms found in elite burials in great house and platform mound sites as well as in local vessel forms used by non-elites living in small unit-pueblos.
Translation: cacao in the Southwest wasn't such a restricted drink after all.
The results are astonishing: 50 of 75 vessels tested showed evidence of theobromine.
Washburn and her co-authors suggest that people from Mesoamerica-- the area beginning around modern Central Mexico and extending to western Honduras and El Salvador that in the 16th century was occupied by, among others, the Mexica (Aztecs), various Maya groups, Mixtecs and Zapotecs-- traded cacao north in return for turquoise from Cerillos, New Mexico.
Now, what I particularly like about that suggestion is that it makes sense chronologically and culturally. One thing that bothered me about the original Pueblo Bonito study was that the model was based on Classic Maya analogies, because the vessels used at Pueblo Bonito, like those used by the Classic Maya, were cylinders. But the dates, which are much more precise in the US Southwest due to the use of dendrochronology (dating sites by annual growth rings from trees), were too late for the Classic Maya to actually be the source of the cacao that made its way up to the US Southwest.
In conversation with my colleague Steve Shackley, who works in the US Southwest, I argued that if we started with the dates — AD 1000-1125 — then we needed to look at likely sources of trade during what archaeologists call the Early Postclassic period. And that, to me, meant we should be thinking about the return trade in turquoise, which became important in Mesoamerica about this time, at sites like Chichen Itza, Yucatan — where, not coincidentally, there are depictions of cacao trees sculpted on some buildings.
While current dating sees Chichen Itza coming apart political about at 1000 AD, other societies that used turquoise for ornaments, including mosaic masks, include the Postclassic Mixtecs of Oaxaca and the Mexica in Tenochtitlan.
The new study by Washburn and her colleagues tested vessel forms they identify as Mesoamerican — including cylinder jar — from 11th century and 14th century sites in the US Southwest. This part of their study replicated the findings of Crown's work — a small group of specialists in ritual were using imported cacao in novel vessels that probably came into use as a package, a kind of chocolate preparation kit.
But Washburn's group also found residues of theobromine in the sherds they submitted as "controls": local pots used by ordinary farmers, where they did not expect to find this imported drink. All of the control vessels tested positive for chocolate.
Washburn and her colleagues end by proposing precisely the kind of exchange I think is most likely: cacao from Mesoamerica for turquoise in the US Southwest. And with their unexpected finding of cacao in the pottery of modest households, they have opened up a door to considering chocolate consumption as something enjoyed by a broader population, not just as a rare exotic good kept by an elite for ritual use.