Archeobotany: Why We Do It, What it Tells Us

This webpage explains the methods and techniques of archeobotanical analysis and interpretation, with emphasis on the importance of archeobotanical studies to Maryland archaeology.

Archeobotany, or Paleoethnobotany is the study of plant remains recovered from archaeological excavations. Archeobotanists analyze this evidence to interpret how people in the past used and interacted with plants. Just as pottery and other objects found by archaeologists allow them to understand a site’s history, plant remains from archaeological deposits are, in fact, “artifacts” that reflect past relationships between people and plants.

Understanding these relationships is rarely simple, as we must base our interpretations on fragmentary evidence. For example:

From a fragment of a burned bean seed we hope to understand the people that bred, planted, cared for and depended upon this food. From tiny fragments of corn we try to understand the variety, culture and importance of horticulture to Indians living in the Chesapeake region.

A bean cotyledon from Idlewild Farm (18AN1257): Gibb 2006.		Maize cupule from the Winslow Site (18MO9): McKnight 2005

And from a fragment of oak wood charcoal we hope to understand the composition and scale of America’s Native forests and the cultural choices which lead to their decimation.

Red oak wood charcoal viewed beneath the microscope.		An oak tree felled in the Monogahela forest ca. 1913. (Fig 11 in Tumult on the Mountains by Roy Clarkson 1964, “photo courtesy of Ruth M. Barrho.”

Areas of specialty within the field of Archeobotany include pollen, starch, and phytolith studies as well as the most widely applied archeobotanical approach: the analysis of plant macro-remains. These are plant materials (usually carbonized) visible to the naked eye and large enough to be identified under low-power (10x to 40x) magnification. Macro-remains include such things as

Carbonized maize cob, burned pumpkin seed and a sunflower achene. (scale 2mm grid).

Plant macro-remains are collected using various techniques, including the recovery by hand of carbon concentrations found during archaeological excavation, water-screening of cultural fill (where water pressure is used to clear artifacts and durable plant remains such as pits and nutshells), dry screening of sediment, and water flotation. One of the most important archeobotanical methods is soil flotation. Flotation is a recovery technique that separates organic matter from the soil using water. This technique greatly enhances the quality and the range of archeobotanical

Soil flotation for the collection archeobotanical material.

Flotation systems vary from simple to complex, but the process involves dumping a sample of archaeological soil into a tank of water. In the tank the heavy material (rocks, shell and cultural artifacts like pottery, lithics, bone, beads and pins) sinks and is captured on a screen. Organic material (wood charcoal, seeds, etc.) floats and is captured in a strainer. Finally, the sediment is washed away, allowing the archaeobotanist to recover plant remains for analysis.

Most plant remains recovered from archaeological sites in Maryland have been preserved through carbonization (burning). Typically, organic materials quickly decompose under normal conditions (imagine your compost heap). However, burning of plant material in a low-oxygen environment can preserve plant artifacts and keep key morphological features intact for millennium. In unusual conditions such as historic wells and privies, or prehistoric bog and cave environments, non-carbonized plant material can persist in the archaeological record.

The products of flotation are dried and the plant artifacts are sent to an archeobotanist for study. Materials are sorted into categories (nut, wood, seed, cultivated plant part) and measurements such as count and weight are recorded. The archeobotanist uses published texts, dichotomous keys and a reference collection of plant materials to identify

An Archeobotanist at work in her laboratory.

The kinds of macro-botanical remains commonly identified from archaeological sites in Maryland include nutshells, wood charcoal, seeds and fruit pits, tree bark, grass fibers, fungi and rinds or husks. Identification of the particular plants present in an archaeological context can help us to understand past vegetation and landscape ecology, seasonality of site occupation, subsistence practices, diet, trade and plant domestication. All existing macro-botanical evidence from Maryland archaeological sites has been organized in the Maryland Archeobotanical Database.

Suggestions for Further Reading on Archeobotany:

Pearsall, Deborah
2001	Paleoethnobotany: A Handbook of Procedures. Second Edition. Academic Press, New York.
Smith, Bruce D.
1992	Rivers of Change. Essays on Early Agricutlure in Eastern North America. Smithsonian Institution Press, Washington D.C.