The fertile and amazingly diverse lowland tropics seem like a likely place for agriculture to develop. But few plant remains survive mold, high temperatures and rainfall. Luckily for archaeologists, one of the ways that plants protect themselves from herbivores and pathogens is to form hardened pieces of silica in their cells. These distinctive inclusions remain as tiny plant fossils called phytoliths, after plants die and decay.
Large phytoliths correspond to the large fruits of domesticated plant varieties in comparison to the smaller phytoliths present in their wild relatives.
Piperno and Stothert compared phytoliths from squash fruits they found in sites on the Santa Elena peninsula in Ecuador to others in a huge reference collection, including wild and cultivated squash species collected throughout the Americas. Larger phytoliths like those found in domesticated varieties of Cucurbita ecuadorensis, the only cucurbit squash native to Ecuador, were clearly evident in undisturbed strata dated to 10,130 to 9320 carbon-14 years (roughly 12,000 to 10,000 calendar years ago).
The carbon remaining from plant cells that survives inside phytoliths was dated using new methods developed by the authors in collaboration with a radiocarbon laboratory.
Hunter gatherers in coastal Ecuador probably took advantage of resources from marine, mangrove and forest ecosystems, and began to domesticate wild squash varieties as they formed fairly stable settlements at the end of the Pleistocene, a plausible scenario for one of the most important economic and social passages of prehistory.
Piperno, D.R. and Stothert, K.E. Phytolith evidence for early domestication in southwest Ecuador. Science. Feb. 14, 2003.
Researchers at the Smithsonian Tropical Research Institute, with headquarters in Panama City, Panama, study the past, present and future of tropical biodiversity and its implications for humankind.
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