Paleoethnobotany is the study of ancient plants. It can be done at a macro scale, where plants can be identified by fragments (seeds, shells, etc.) observable by the naked eye or at the micro scale, where microscopes are required to observe and identify plant remains. I have worked at both the macro scale, using a technique called macrobotanical analysis, and the micro scale using a technique called starch grain analysis. See below to learn more about the these different techniques.
Macrobotanical analysis is used to identify carbonized plant remains from archaeological contexts. The presence of these remains can often be observed with the naked eye, but microscopes are often used for the identification of the plant. Archaeologists often use a process called “flotation” to recover these remains. Carbonized plant remains will float to the surface when immersed in water, where they can be scooped up, dried out, and analyzed by specialists. The study of macrobotanical remains can be used to reconstruct ancient diets. In cases of excellent preservation, can be used to identify contents of individual pots. Macrobotanical analysis can also be used for the reconstruction of ancient environments (paleoenvironmental reconstruction).
Starch Grain Analysis
Starch grain analysis is a microscopic technique that allows archaeologists to identify remains of plants, like tubers, fruits, and grains, that have starchy parts. This analysis requires specialized lab facilities to process. When viewed under a microscope, individual starch grains can be identified by characteristic features like their size and shape. Archaeologists can look for starch grains on artifacts, like stone tools or ceramic vessels, to understand how they were used. Starch grains can also be found in soils where these foods have long since disintegrated. For example, we could test soils from an ancient trash dump to see what plants had been thrown out. Or we could test a kitchen floor to see what plant foods were being processed there. Starch grains can also provide information on food processing techniques, like heat treating, heavy grinding, and fermentation. Starch grains also preserve well even in wet conditions and can often be recovered from sites where other plant remains disintegrate.
Maize starch grain recovered from a ground stone fragment at Izapa. Four different light settings illustrate different features that help with identification.
Maize, or corn, is often considered the lifeblood of Mesoamerican peoples. But maize was just one part of a broad spectrum of plant foods that comprised the Mesoamerican diet. Ancient Mexican peoples also relied on other foods, like chili, cacao (chocolate), sweet potato, manioc, and tropical fruits to supplement their diet. While maize agriculture has often been cited as an important cultural trait that serves to unify Mesoamerican cultures, a restricted emphasis on this one food source masks the impressive regional variability in human-environmental relationships across the many environmental zones encompassed within Mesoamerica, including highlands, tropical forest, coast, and desert.
My current work applies starch grain analysis to define which other plant foods played important roles in the diets of coastal peoples for a continuously occupied region in Mesoamerican prehistory: the southern Pacific coast of Mexico. I am investigating plant remains from the site of Izapa, a settlement that was occupied for nearly 3,000 years (1900 B.C.-A.D. 1000), through droughts, volcanic eruptions, and the collapse of several prominent Mesoamerican civilizations, like the Olmec and the Maya. Documentation of the diversity of plant foods used by Izapa’s population will help to better understand the resilience of this coastal population, especially for periods of drought and volcanic activity, when maize agriculture may have been a less reliable source of food.
The samples I am analyzing were recovered from artifacts, like ceramic vessels and grinding stones, as well as cultural features, like floors and trash pits, during my Izapa Household Archaeology Project excavations in 2014. I am currently (2017-2018) undertaking this research as a postdoctoral fellow at the Smithsonian Tropical Research Institute’s Center for Tropical Paleoecology and Archaeology in Panama, working in collaboration with Dolores Piperno and Irene Holst. Pilot studies were conducted in at the Instituto de Investigaviones Antropológicas at the Universidad Nacional Autónoma de México in collaboration with Guillermo Acosta Ochoa and Jorge Cruz Palma .