Chocolate domesticated earlier than thought

Chocolate, long recognised as a critical cultural artefact in early Central American cultures, may in fact have been domesticated 1500 years earlier than thought, and significantly further south.

In a paper published in the journal Nature Ecology and Evolution a team of researchers led by archaeologist Michael Blake of the University of Calgary in Canada present three lines of evidence they say points to the cultivation of cacao (Theobroma cacao), the plant from which chocolate is derived, in the Santa Ana-La Florida region in south-east Ecuador at least 5450 years ago. That’s a millennium and a half before its earliest known occurrence in pre-Columbian Meso-America.

Because of its well documented ritual and nutritional importance in the region, it has long been assumed that cacao was domesticated in Central America, where its use has been dated to as early as 3900 years ago. It was adopted by the people of Mexico around 1000 years ago.

Blake and his colleagues, however, provide evidence that strongly suggests that T.cacao was cultivated and used much earlier. Their research extends from an earlier genomic study that found the plant shows the greatest genetic diversity in the forests of the upper Amazon.

To explore whether the apparent abundance of the plant in that region was associated with its use by the people resident there at the time, the researchers tested a selection of ceramic bowls excavated since 2002 at Santa Ana-La Florida, the earliest known archaeological site belonging to the Mayo-Chinchipe culture.

With radio-carbon techniques already dating the site – a village comprising approximately 20 buildings surrounding a central, sunken plaza – to 5450 years before present, the scientists looked for any evidence of T.cacao still present on ceramics.

They found plenty. The study documents the discovery of cacao-specific starch grains on the interior of the pots, fragments of DNA comprising sequences unique to the plant, and residues of a specific alkaloid called theobromine, which is present in domesticated cacao but not, tellingly, in its wild relatives.

“To our knowledge,” the researchers conclude, “these findings constitute the earliest evidence of T. cacao use in the Americas and the first unequivocal archaeological example of its pre-Columbian use in South America. They also reveal the upper Amazon region as the oldest centre of cacao domestication yet identified.”

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