Day 16- The Role of Pollen in Archaeology
First,
a huge thank you goes out to Dr. John G. Jones, Associate Professor of
Anthropology at Washington State University, who was our guest lecturer for
this lesson. He exuded energy and passion for the topic of palynology, opening
his lecture as a tale of sex, adventure, and romance all about pollen. Needless
to say, this gentleman was a true character, and equally kind to us students as
he was to the professional staff.
Pollen
is essentially and simply plant sperm with an outer shell made out of the
genetic material, sporopollenin, which is the tough outer walls of spores and
pollen grain, which is chemically very stable and is usually well preserved in
sediments. Pollen is capable of being extracted from coal, and a 310 million
year old pollen sample was found from a shale fragment from Mongolia, pollen
will last. The only exceptions to this are when fungus or bacteria destroy the
pollen.
Insect
pollination is the most effective- plants attract bugs with pheromones from
flowers, some plants make very little pollen and use their pretty flowers or fragrance
to attract the insects to carry their pollen, or in the case of the pine tree,
the plant may make a ton of pollen, pine trees make a billion polygrains in
order to reproduce. Pollen wears and weathers out of rocks and people then
breathe them in (allowing for location of bodies for example).
Pollen
studies are used in fields such as the oil industry, medicine, bee keeping,
forensic science, and of course, archaeology. In the oil industry, the oil has
to be a certain age and maturity before it produces, so it is necessary to know
how old the maturity of the sediment is, and whether it holds oil or just gas. Approximately
91% of all palynology worldwide is for various oil industries, which pays about
$500 a sample, with about 4,000 samples requested a day as “rushed work,” and
the lab receives 10% of the profits. Pollen is used in medicine for allergy
testing. For example, a single vile of ragweed is $450 and is needed for all
main allergy testing done by doctor’s offices. Forensics uses pollen testing
just as you have probably seen in any criminal drama television show, such as
Law and Order, or Bones.
Most
importantly pollen is used in the field of archaeology, mostly coprolites
(fossilized feces), and as Dr. Jones likes to say, “Pull up a stool, I’ll tell
you all about it.” As in many cases, the bathroom holds the key to the way a
society ate and lived. A stool can tell us the origins of agriculture,
deciphering the earliest crop dates, and agriculture style (burning,
fertilization, etc.). The sediment at Monticello perfectly conserves the pollen
from oxidization which kills pollen, and the thick red clay also coats the
pollen grains, keeping fungus from killing the pollen. Palynologists have, for
example, taken pollen samples from ground stone to tell what people were
harvesting, preparing, and eating.
The
process of pollen soil sample is extremely complicated. The first step is to
dissolve the soil away, leaving the pollen. Hydrochloric acid is used to
isolate the pollen, then sands, silts (silicas) are removed with hydrochloric fluoride,
the sample is then washed in potassium hydroxide, which can dissolve skin, but
leaves the pollen, and in order to remove the organics acetolysis is used, it
is explosive in water, but leaves the pollen, the minerals then need to be
removed, a pyrite and tourmaline causing the minerals to sink and the pollen to
float. The Monticello soils are very difficult to clean, due to the thickness
of the clay, and not all pollen collected is identifiable.
Corn
(maze) barley, oats, and wheat, along with all grass have similar looking
pollens. The oldest maze pollen to have been located to date goes back to 52000
BCE and was produced by plants which did not produce corn cobs, yet still produce
a sugary rich stem. Maze in the new world was possibly first domesticated to
make sweet beer brew (honey was in Mesoamerica and cocoa), sweets from corn is
brewable from the stocks.
Pollen
in archaeology is taken with soil cores, samples from parts of the ground never
exposed to oxygen, and core samples, used for radiocarbon dating (the chronological
record of changes in pollen throughout time). A vibracore collection allows for
the soil to be brought to surface without disrupting the sediments. Pollen
samples are also collected from sidewalls (profiles) of the strata of a quadrat,
what is known as a profile pollen sample, which means that every 5cm of the
sidewall a pollen sample is collected from the bottom-up, and then a pollen
diagram is created to illustrate the break-down of certain pollens.
Aside
from pollen, phytoliths (siliceous plant remains) can also be useful in
archaeology. Phytoliths are produced within cells of plants, and are strong in
areas where pollen is weak. Whereas with pollen, grass could not be identified,
with phytoliths grass is identifiable. The smaller the sample of phytoliths,
the better the integrity, and these samples should be taken from the center of
your feature (i.e. sub-floor pit found in quadrat). Both pollen and phytoliths
are simply more key pieces to the historical puzzle which archaeologists are
charged with attempting to solve over years of collecting and putting together
piece after piece- slowly but surely.
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