Archaeobotany is the study of archaeological plant remains.
One of the primary questions in archaeology concerns the origins of agriculture and the identification of early domesticated plants.
The origin of maize provides a useful illustration of what archaeobotanists do.
Maize was domesticated with the last 10,000 years.
The pursuit of the ancestors and timing of the domestication of corn has proven difficult.
Most favor the wild Mexican grass known as teosinte.
Determining the antiquity of the domestication of maize is also difficult.
Maize is now argued to have been domesticated around 4200 B.C. somewhere in southwestern Mexico.
Dates given for the earliest corn in South America are sometimes earlier than the dates in Mesoamerica.
Humans have used plants as long as we have been human.
In addition to food, plants fill many other needs as well.
The preservation of plants at archaeological sites is generally poor.
Plant remains are often fragmentary and identification is difficult.
Archaeobotanists want to know what plants are present at a site.
Separating and sorting is required.
Plants provide useful information on the seasonality of site use.
Botanical remains also tell us about the natural environment around a site.
Both macroscopic and microscopic plants remains are studied.
Archaeobotanists can extract and study ancient DNA in plants.
Macrobotanical Remains
Macrobotanical materials are visible remains like seeds, nutshell, and other plant parts.
They are likely to be present at a site due to direct human contact or utilization.
Besides food resources, plants may also be used for the production of textiles, mats, and baskets, for making poison for arrowheads, or as drugs, as examples.
Casts of plant remains in ceramics and accidentally fired clay sediments provide information as well.
Flotation
flotation.
Flotation involves drying excavated sediments and then pouring them into water.
The lighter, carbonized plant fragments (the "flot") rise to the top and float.
Sorting and Identification
The majority of the identifiable macrobotanical remains are recovered during wet screening and flotation.
This material is taken to laboratories where drying facilities, good lighting, and microscopes are available.
The macrobotanical remains are first sorted by size and shape and identifiable pieces.
The majority of the sample material will lack diagnostic features and cannot be identified.
The use of a comparative collection of reference materials is essential.
Identification is a demanding job.
The result of the sorting and identification process is a list of the species present and counts of their abundance at the site.
Example: The Incinerator Site
Fort Ancient is the name for a time period and archaeological culture in the Eastern U.S, around AD 1000-1500.
Communities were focused on a narrow range of food resources.
Such societies are subject to repeated, short-term seasonal shortages that can be ameliorated through storage practices.
Fort Ancient people were maize farmers, relying on a few plants and animals for most of their food.
Deer, elk, and black bear supplied 80% of the meat.
Their diet was approximately 80% maize.
Residential groups gathered in larger villages of permanent houses in the spring and summer.
During the fall and winter, family groups dispersed to hunting camps.
The Incinerator Site is located in southern Ohio.
The site was occupied for a short period, perhaps 15-20 years, around AD 1250.
Many pits at the site were used for food storage.
Almost 40 of these pits could be assigned to a season of use.
The identification of the charred macrobotanical remains in the pits allows for the determination of the diet for each season.
Pits from the different seasons contained the same kinds of plant foods.
The information indicates that plants were essentially available year-round to the inhabitants.
Protecting The Past: Sunwatch Indian Village/Archaeological Park
The Incinerator or Sunwatch site was declared a National Historic Landmark and protected for the future.
The site has become the Sunwatch Indian Village/Archaeological Park.
There are five reconstructed buildings and a partially reconstructed stockade, as well as a museum and gift shop.
Origins of Agriculture
Agriculture represents one of the major changes in the evolution of human culture and an important focus of archaeobotany.
An important distinction in agricultural plants is made between seed crops and root crops.
Most of the evidence for early domesticated plants comes from seed crops.
The best known early domesticates are the cereals.
They were often burned during preparation or cooking.
Root crops such as potatoes, yams, manioc, and taro may also have been domesticated early.
But root crops are not well documented in the archaeological record because they lack hard parts that are resistant to decay.
In addition, because they reproduce asexually, it is difficult to distinguish domesticated varieties from their wild ancestors.
Archaeologists have started to identify root crops from prehistoric sites only recently.
Seed crops remain the focus of most research on the origins of agriculture.
One of the important hallmarks of plant domestication is an increase in the size of the seeds or grains of the plant.
An important characteristic of a domesticated species is the loss of its natural seeding ability.
Another major change in domesticated plants is the human removal of plants from their natural habitat to new environmental zones.
New conditions of growth select for different characteristics.
Some varieties do very well when moved to a new setting.
Archaeological Thinking: Domesticating Plants
An important question about the origins of agriculture concerns how long the process of plant domestication takes.
The question of how to determine the length of time for domestication is difficult.
Archaeobotanist Gordon Hillman studied wild einkorn growing today in the Near East and conducted a number of experiments involving sowing, harvesting, and storage.
He found that morphological changes could only be observed when selective harvesting and other cultivation techniques were involved.
Example: Abu Hureyra
Abu Hureyra was a large tell that contained layers of occupation from approximately 10,500 B.C. to 6000 B.C.
The mound covered 30 acres with deposits from the Preneolithic and the early Neolithic.
The mound lies at the edge of the Euphrates River.
Wild grasses, probably no more than 1 mile distant, included wild wheats, rye, and various pulses (lentils and legumes).
Gazelles were killed in great numbers during the spring migration.
The Preneolithic settlement consisted of small, circular pit dwellings dug into the original ground surface.
The first phase of occupation was between approximately 10,500 and 9000 B.C.
The population was between 200 and 300 inhabitants.
The bulk of their food came from wild plants, some of which were staples.
Around 10,000 B.C., the climate became cooler and drier.
Nearby stands of wild cereals retreated more than 62.5 miles to the higher elevations of the Fertile Crescent.
Wild wheats continued to be consumed at the site.
The Preneolithic inhabitants cultivated wild cereals before the changes indicating domestication were evident.
By 8500 B.C., the range of domesticated plants included rye, lentils and large-seeded legumes, and domesticated wheats.
Two tons of animal bone, antler, and shell also were recovered during the excavations.
Inhabitants obtained food from the Euphrates River as well as from the surrounding hills.
By the beginning of the Neolithic, sheep and goats had been domesticated.
During the subsequent phases of the Neolithic, domesticated cattle and pigs were added to the larder.
Abu Hureyra became the largest community of its day, with 2000 to 3000 inhabitants.
The importance of the town is documented by the quantity and variety of exotic materials that arrived there through trade and exchange.
By 6000 B.C., Abu Hureyra was abandoned.
A similar pattern is seen at other Neolithic sites in the Levant at this time.
Wood and Charcoal Identification
Charcoal is the term that archaeologists use for the heavily burned fragments of wood and other plant tissues.
Because it is largely inorganic, it will preserve when other organic materials disappear.
Charcoal often can be identified as to species.
Scanning Electron Microscope studies have been able to identify charred parenchymous tissues.
Parenchyma is the most common plant tissue.
Analysis of parenchyma is useful for identifying roots and tubers.
Science in Archaeology: The Scanning Electron Microscope
The Scanning Electron Microscope (SEM) is widely used in archaeology to obtain high-resolution images of artifacts and other materials.
The SEM can provide 3-dimensional images at magnifications hundreds of times greater than most optical microscopes.
Example: Wood Charcoal from Thera
Thera is one of many islands in the Aegean Sea.
In 1700 B.C., Thera was a volcanic cone.
The volcano must have been relatively stable at that time since its lower sides were heavily inhabited.
The town of Akrotiri stood on its southern flank just at the coast.
Thera erupted in 1500 B.C.
Akrotiri was abandoned and the inhabitants fled the island.
Large parts of the town of Akrotiri were buried in ash.
A recent study of wood charcoal from the site of Akrotiri has provided evidence on the availability of various plant species.
Results have shown a variety of species present and an abundance of material.
Trees were widespread on the small island.
Cedar, yew, and beech were imported to the island.
This documents large-scale shipping and trade in the western Mediterranean Bronze Age.
Microbotanical Remains
There are several different kinds of microbotanical remains, or plant microfossils, used for studying past vegetation and environments.
Spores and pollen are the coverings of the gametes of terrestrial plants that are released in sexual reproduction.
Phytoliths ("plant rocks") are another microscopic form of evidence for plants.
Diatoms are aquatic unicellular plants, a microscopic algae.
The microscopic grains of starch that certain species of plants produce are another microfossil of interest.
Archaeobotanists study specific kinds of microfossil remains depending on what they want to know and what is preserved.
Spores generally are used for species of plants in deposits that are much older than the human presence on the planet.
Diatoms are very useful for studies of seas and lakes.
Only a few applications have been reported for starch.
Phytoliths have been employed to argue for early agriculture in South America.
Pollen is the most commonly studied of the microfossils.
Palynology
Palynology is the term used for pollen analysis.
The pollen plants produce often survives in the archaeological record.
Plant pollen is very, very small and weighs almost nothing.
Pollen grains are protected by hard shells that are impervious to water and most soil acids.
Types of pollen are very specific in shape and size and can be identified to the genus or even species of plant that produced it.
Pollen can be used to provide a picture of past vegetation, climate and environmental conditions.
The palynologist uses a high power microscope to identify the species present and counts the grains of pollen of each type that are found.
Certain marker species or changes in the pollen record may aid in the recognition of prehistoric settlements or cultivation practices.
Example: The Elm Decline
Pollen analysis began in northern Europe.
Scientists made pollen diagrams of the vegetations for the last 10,000 years.
Pollen was analyzed in southern Scandinavia.
Climate changes occurred starting around 15,000 years ago.
Originally, there was a fresh and barren land surface.
Over a period of 8,000 years, this changed to open coniferous woodlands, and then to a dense, dark forest of deciduous trees.
There was a precipitous decrease in elm pollen around 4000 B.C.
A number of reasons for this decline have been suggested.
Human interference with elm was a popular explanation for many years.
Suggestions included both tree felling for field clearance and the clipping of elm branches to use for animal fodder.
New information obtained in the last decade suggests Dutch elm disease.
