Paleoethnobotany, also known as archaeobotany, is
the subdiscipline of archaeology that studies how plants were used by
prehistoric societies. Until the mid-19th century, paleoethnobotanists
did not work at the site, relying instead on other
archaeologists to gather materials in the field. As the discipline
developed, however, the need to ensure that appropriate sampling
strategies and analyses were used in collecting and organizing samples
prompted archaeobotanists to go on-site to collect their own data. They
could then more accurately interpret the uncovered organic remains to
determine the importance of various plant life to the area's former
residents.
Under normal conditions, of course, plant remains
tend to decay very quickly; but organic material that has been
carbonized by charring may survive for extended periods of time.
Consequently, paleoethnobotanists focus on sifting through hearths and
middens (dunghills and refuse piles) in an effort to extract material
that will provide clues as to how plants were utilized by the site's
former occupants. The study of an individual fireplace is likely to
reveal only what was burned there in the last fires or perhaps just the
final fire (although study of multiple fireplaces may offer cumulative
evidence); refuse dumps are able to provide a better indication of the
lasting patterns of consumption and are therefore more likely to yield
enough statistical data to allow the archaeologist to reach meaningful
conclusions.
As a rule, material scooped up on-site is usually a
mixed bag of plant remnants combined with soil, bone, and animal dung.
The primary means of separating the plant remains from the other media
is the flotation process. A simple but time-consuming and painstaking
task, the flotation process is built on the assumption that organic
material--seeds, fibers, and so on--generally floats, and inorganic
material--sand, shells, or ceramics--generally does not. Using a series
of graduated sieves, often nested together, archaeobotanists are able to
filter plant remains from other debris. Because the collected material
tends to be desiccated, charred, or waterlogged, it is extremely
fragile, and tweezers or a small paintbrush may be necessary to remove
substances from the sieve. It is dirty work, at best, but ultimately
very revealing to the
botanist.
Once sorted, organic remnants are generally
reviewed using a process called reflected light microscopy. Specimens
are razored to reflect three anatomical planes (transverse, radial, and
tangential) and studied under a
microscope. Species are sorted, identified, and cataloged, and
accumulated data are then analyzed and interpreted and, often, fiercely
debated, reconsidered, and reinterpreted as additional material is
gathered. Because in some areas of the world local customs have changed
little over time, paleoethnobotanists may also look to contemporary
village life for guidelines to assist them in interpreting their
archaeological findings.
Within the field of paleoethnobotany is the subspecialty of
palynology, or pollen analysis. Just as a seed is unique to an individual plant, so too is
pollen, and similar to charred seeds, pollen may be preserved under
proper conditions for long periods of time in soil and rock formations.
Analysis of the pollen
fossil record reveals what plants grew in a given area during a particular era, thus allowing palynologists to infer the
climatic conditions that would have been necessary to support such
plants (temperature, rainfall, growing season). Comparison of these
findings with current climate conditions in various parts of the modern
world provides evidence of environmental change, allowing palynologists
to conclude, for example, that the climate prevailing in one area 5,000
years ago was similar to the current climate in an area 1,000 miles
(1,600 km) to the north of the subject locale.
What, then, does paleoethnobotanical evaluation
tell the archaeologist? First, it provides information about how local
vegetation was used by inhabitants for fuel, food, and the construction
of houses and boats. Further, the collection of plant material allows
the paleoethnobotanists to make
anthropological deductions about multiple aspects of
prehistoric culture and environment, including the process and timing of plant cultivation and
animal domestication, the development of trade practices and local
industry, the occurrence of demographic change, and alterations in
climatic conditions, as well as to hypothesize as to the reasons why
these shifts occurred.
By enhancing our knowledge of how ancient peoples
lived, paleoethnobotany helps us understand and appreciate the role
humans play in altering their environment. For example, certain cultural
changes once thought to be caused by climate shifts, such as drought,
are now believed to have been caused by population growth and the
resultant deforestation, overgrazing, or soil exhaustion of farmland. In
cases such as these, the study of paleoethnobotany can not only teach
us about the past, it may also provide a lesson for the future.
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