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.