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Pollen and Starch Analysis
Pollen analysis can be a good
tool for examining both the paleoenvironment and also cultural
records, including evidence of diet and food processing. Starch
analysis is valuable primarily as an additional tool for
examining food processing and diet.
Paleoenvironment
Pollen
are relatively durable in many sediments, as well as in bogs
and lacustrine deposits. Tree (arboreal) pollen, which
is released several feet to several 10s of feet above the
 ground,
usually travels well on the wind, providing a record of trees
growing in the region. In fact, pine pollen (pictured
at right) is known to travel up to thousands of miles.
Shrubs, which are not as tall as trees, release their pollen
at a lower level. Although pollen from some shrubs,
such as Artemisia (sagebrush) travels well on the wind,
this is due, at least in part, to the fact that it grows in
areas where wind movement is not hampered by a dense growth
of trees. Grasses and forbs, which grow even lower to
the ground, release their pollen relatively close to the ground.
Usually this pollen is not as available for wind transport
over long distances (tens to hundreds of miles). These
are just some of the dynamics that contribute to pollen transport
that produces ambient or local pollen rain.
Use of pollen as a proxy for
past vegetation often provides valuable information concerning
the paleo environment. Not only can one describe past
vegetation; it also is possible to interpret vegetation
communities and the associated climatic conditions that might
have led to community formation. When interpreted by an
experienced palynologist, a stratigraphic pollen record provides
information concerning both local and regional vegetation.
Therefore, it is important to select an appropriate site to
sample. A stratigraphic column inside an archaeological site
will reflect intensive activities by human occupants of the
site, as well as disturbance by long-term occupation. A
stratigraphic column collected slightly outside the living area
of a prehistoric site often provides a cleaner record of
paleoenvironmental conditions. Care must be taken to tie the
stratigraphic layers to those in the site. Sometimes a
stratigraphic column is better collected within the living areas
to examine all of the stratigraphic layers present there. |
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Food
Processing and Diet
The
pollen record  has
the potential to inform concerning use of plants that have
been processed for food or medicine, or any number of other
uses. In fact, construction elements
of dwellings are sometimes represented in the pollen record,
such as use of sagebrush in constructing the superstructure
of a housepit. Use or processing of plants as foods
or medicines often is well represented in the pollen record.
In areas with agriculture,
Zea mays (corn, maize)
pollen often is noted in samples from floors, niches, benches,
storage pits, near hearths, in hearth deposits, and in washes
of ceramic vessels and groundstone, to mention but a few
locations. Pollen from gathered plants
such as Cheno-ams, Cleome (beeweed), Opuntia
(prickly pear cactus), and a large variety of other plants
often is either present or present in an elevated frequency
in areas as a result of food processing activities.
One means of identifying food
processing areas within any bounded space (structure, room,
patio, etc.) is to grid the floor and collect samples from
each grid, noting proximity to features. This provides a map
of evidence of plant use across the floor. We have found that
pollen analysis of compacted floor sediments is more
productive than macrofloral analysis, although for floor fill,
which is looser, both pollen and macrofloral analyses are
productive and complementary, rather than duplicating
information.
Washing groundstone is a much
more direct measure of plants that might have been processed,
rather than collecting sediments under or next to
groundstone. We have developed methods of washing groundstone
to minimize recovery of post-depositional sediment, thus
reducing the added background signature. If it is possible to
wash groundstone or ceramic sherds or vessels to recover
pollen, phytoliths, or starches that might represent plants
processed, this should be done. Sediment samples can be
collected as controls.
Starch
Starches
should be "food
for bacteria and other soil micro-organisms", but as
with all things in nature, it is an imperfect system.
Some of the starches simply survive. Starches provide
a particularly good record of roots/tubers that were processed
because these foods do not leave seeds or pollen. When
roots/tubers are collected when the plants are in flower,
the flowers transport pollen to the processing area, which
allows portions of the pollen record to represent collection
and processing roots/tubers. However, when roots/tubers
are not collected when the plants are in flower, there is
no transport mechanism. Many starches survive our pollen
extraction process, meaning that we can identify them when
we see them in pollen samples. As a general rule, starches
from roots/tubers have eccentric hila (that means their hilum,
which often appears as a dark spot under the microscope) is
off-center. Seeds, on the other hand, usually produce
starches with centric hila. A cross-polar illuminator
(or crossed nichols) are necessary to examine starches well
enough to identify them. Some starches have a rather
generic form, while others are specific to either genus or
species. Many plants produce several different types
of starches in a single organ, meaning that one must learn
to identify populations of starches, rather than relying on
single starches. We have noted starches in human tooth
calculus, groundstone washes, ceramic washes, washes of Poverty
Point Objects, floor samples, other sediment samples, and
in nearly every type of provenience that we have examined
for evidence of food processing.
Ethnobotanical
Leaflets Starch Research Page - by: Don Ugent
and Linda Scott Cummings
   
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