Preservation of Organic Materials
The artifacts found at a site are often not the truest reflection of what once existed at that site. Often most artifacts are degraded through natural processes. These processes effectively reduce the number of artifacts preserved by a great percentage. However, many different factors can increase the post-use lifetime of organic materials. The most general causes for degradation are water and oxygen, and locations without those encourage the preservation of organic materials.
Some examples of locations that prevent degradation are dry areas (no water), wet areas (no oxygen), high altitude areas (less oxygen), and cold areas (no liquid water). Examples of these and what has been found in them are listed below.
Wet areas: Areas that are very wet often contain little oxygen. This increases the life span of organic materials. There are several examples of this. The first example involves times of heavy rainfall. Many living creatures, such as earthworms, cannot make use of Oxygen dissolved in water. This is a problem for them during periods of substantial rainfall. Large amounts of water poring through the soil forces the oxygen trapped inside of the soil out, removing the oxygen the worms need to breathe. This causes the worms to come to the surface, as we can see when they lie on concrete or blacktop surfaces after a storm. This is not overly important in the preservation of organic materials, but it is an obvious example of the effect water can have on organic life
The second example deals with a particular type of lake or pond. As everyone knows, many lakes have fishes in them. However, not all bodies of water do. Some, like the dead sea, have too high of a salt content for multicellular eukaryotes to live in. Others have a lack of oxygen. Lakes that do not contain oxygen are called merimatic. They can be 100% oxygen free, which is rare, or only the lower levels may be void of oxygen. An example of a merimatic lake is Crawford Lake, found near the Canada/New York boarder just above the Niagra Escarpment. This lake is approximately 24 meters deep, and the last 12 meters of it contain no oxygen. This is important to archaeologists, as it means that whatever falls in the lake and sinks to the bottom will be preserved. At Crawford lake, this benefit was used by analysing the layers of pollen (one from each growing season) found on the bottom of the lake. This enable archaeologists to determine the type of crops being grown by local Iriqouis, as well as the amount of crop (based on the thickness of the layer). This led to better estimates of occupation size and time, and has been used in several similar cases.
The third example involves swamps, bogs, and peats. These areas are wet marshes that contain not just water, but also other materials. These materials often give off gases themselves, and these gases frequently displace the oxygen in the mire. Therefore, there is no oxygen to help degrade whatever artifacts or ecofacts may be present in the mix. This has proven useful in turning up everything from ancient wooden cats to partially preserved people at different sites. (note: this segment will soon be expanded upon with more specific examples).
Dry areas: Areas that are very dry do not have very much water (hence, they are dry). This means that the degradation process is again slowed down. This has produced a remarkably high yield of surface artifacts in such regions as the American Southwest and the highlands of Mexico, especially ceramics.
Cold areas: I'm sure most people remember reading about the Mars rock found in Antartica that may contain evidence of extraterrestrial life. Well, the findings of the initial study may or may not be true, but it does help demonstrate how well preserved artifacts can be in cold, dry areas. Put another way, until that rock was picked up, it had lain virtually undisturbed for the entire course of human history. This benefit, however, is not too frequently used, as not too many studies have been done in the extreme cold (although there have been some, especially on the tundras in the northern hemisphere, and these will be discussed in greater detail in the upcoming weeks).
Thank you for reading this far. This area will be updated shortly, as will the genetical anthropology location.