Tiny Phillips Academy Museum Harbors Clues to Ancient Origins of Corn

Contributed by Ryan Wheeler

Archaeologist Richard S. MacNeish—known as Scotty—devoted his career to untangling two of the biggest questions of archaeology: when did people begin domesticating plants and how did that act impact and influence the development of civilization? During his tenure at Phillips Academy’s Robert S. Peabody Museum of Archaeology MacNeish led multidisciplinary expeditions to Mexico and Peru to search for the heartland of domesticated maize or corn. Before his death in 2001 MacNeish had searched for the origins of rice cultivation in China, studied early cultures of Belize, and planned to look at wheat domestication in Turkey. Evidence for domestication often could be found in dry caves, where ancient plant remains were preserved. Speaking of his research in China, MacNeish quipped, “I’ve crawled in and out of more caves than a Neanderthal caveman.”

Image of Scotty MacNeish.
Scotty MacNeish reviews excavation profiles.

Despite MacNeish’s indefatigable quest for the origins of the world’s most important crops, answers remained elusive. In Mexico’s Tehuacán Valley, near modern-day Puebla, MacNeish and his team reconstructed ancient environments, devised chronologies, and documented a sequence of corn domestication from tiny, primitive cobs to those that look much like the corn that was growing in the area during the Spanish conquest in the sixteenth century. MacNeish’s suggestion of an early date for corn domestication, however, was met with skepticism, as many archaeologists believed that these crops were developed after significant strides in social organization, urbanism, and the other hallmarks of civilization. A debate ensued, but much of MacNeish’s Tehuacán research was sidelined as other scientists found evidence for even earlier sites of corn domestication in the Mexican lowlands, pushing the dates back to at least 8,700 years ago.

Image of excavators working in Coxcatlan Cave, Tehuacan Valley, Mexico, 1960s.
MacNeish’s 1960s excavations at Coxcatlan Cave, Tehuacán Valley, Mexico.

MacNeish’s collections, preserved since the 1960s at Phillips Academy’s tiny Robert S. Peabody Museum of Archaeology, have continued to attract the interests of scientists. A November 21, 2016 article in the journal Current Biology reconstructs for the first time ever the complete genome of an early domesticated plant, based on a tiny, 5,310 year old cob from MacNeish’s Tehuacán project (Catalog number 90.184.36). The specimen was removed from an old exhibit case several years ago and loaned to the Smithsonian Institution’s Bruce Smith, a co-author of the new study. Statistical analyses of the DNA data indicate that the study specimen, dubbed Tehuacan162, is “a step that links modern maize with its wild ancestor.” Of particular interest were genetic markers for domestication—some of which were already exhibited in this early specimen—while others were not. This challenges previous models for corn domestication that focus on two major steps, countering that the history of domestication is more gradual and complex than currently believed. In conclusion, the study finds that Tehuacan162 is an ancient form of maize that is closely related to the ancestor of all modern maize, yet distinct from teosinte, a wild grass that is the closest living relative to maize.

Today the Robert S. Peabody Museum of Archaeology provides educational programming to the high school students of Phillips Academy, ranging from classes to work behind-the-scenes with our significant collections. Researchers also are encouraged to use the Museum’s holdings and often share their results with students.

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