Knight, George C., and James D.
Keyser. 1983 A Mathematical Technique for Dating
Projectile Points Common to the Northwestern Plains. The Plains Anthropologist
28(101):199-207.

Plains
archaeologists often encounter lithic projectile points dating from the Archaic
and Late Prehistoric periods that are not in their original stratigraphic
layer. This makes dating these stone
points using radiometric or other dating methods impossible. However, using statistics, Knight and Keyser
have been successful in providing a method to determining the approximate date
of certain lithic tools, specifically projectile points. Although their article only describes
differentiating between two time periods in a subsection of the plains with a
very specific subset of tools, their high success rate shows that their methods
should be applicable to other regions and time periods.

In
order to calibrate their statistical formulae, the authors needed a large
sample size of projectile points with known radiometric dates. Fortunately, this data is not scarce. The specific statistical method they used is
called discriminant analysis (DA), which specifically applies to the testing of
an object, and placing it in two distinct categories using statistical
significance. Using abundant student
help, these researchers measured thousands of projectile points from the time
periods, and derived functions that described the various notch widths, heights
and lengths. Using an adequate number of
digits to reduce error, the authors were able to achieve a 96% rate in
identifying unknown projectile points.
The authors, however, did not stop there. They realized that projectile points are
often incomplete. Knowing this, they
provided further statistical analyses to help determine the period of the respective
projectile points using only a single variable, in their case the neck width.

The
method of determining the time period of a given projectile point using the
method given by Knight and Keyser proved to be quite simple. In the article, two equations are given. Simply inputting the measured characteristics
of a projectile point into both equations gives two values. The equation that gives a larger value is the
correct one. Using this relatively
simple method expanded to other locations and time periods, tools can be more
effectively dated suffice the sample size that is radiometrically dated is
adequate.

Caldwell,
Warren W., and Lynn M. Snyder. 1983 Dendrochronology in Plains Prehistory: An Assessment.
The Plains Anthropologist 28(99):33-40.

It
is a well-known fact that absolute dating methods are far more desirable than
relative dating systems in archaeological excavations.
Dendrochronology, or tree-ring dating, is one such absolute dating
method. Although this system gets much
more use in the wooded forests of the world, it still has some utility on the
plains, where limited tree growth restricts the overall number of trees that
have been preserved that are able to be dated.
The plains also receive a medium amount of moisture, which means that
the preservation processes that are much more likely to occur in extreme
moisture and extreme lack of moisture almost never occur on the plains. In addition, many tree species on the plains
are unsuitable for dating, for various reasons including inconsistent growth seasons,
and erratic development. Despite these
setbacks, dendrochronology was a growing field at the time of this articles
writing, although it was quickly being surpassed by radiometric methods. Archaeologists of the plains were willing to
use dendrochronology, regardless of the veracity of the results. Since tree ring dating is extremely difficult
to check properly, archaeologists often asserted incorrect dates not realizing
their errors. Their major flaw was using master tree ring lists from a distance
away that they would not apply at the location of the excavation.

Realizing
the errors that had been made, several groups, such as the Missouri Basin
Chronology Program, attempted to create master tree ring lists for all of the specific
region on which they were focusing, and then clearly defining accuracy based on
distance from the wood sources.
Radiocarbon dating was also used to supplement this data. The dates were found to be inconsistent,
however, and dendrochronology was discarded.

Caldwell
and Snyder attempt to show why this apparent inconsistency occurred across
virtually all tested samples. On
average, the pair showed a discrepancy in the oldest houses from between
600-850 years. This huge inconsistency
calls into question not only dendrochronology, but also radiocarbon dates for
plains tree samples. To try to determine
why, the authors carefully took recent samples of relatively known age and
dated them. The inconsistencies found
previously did not resolve themselves completely. This would mean that the entire timeline of
the Plains would be inaccurate. It is
likely that a more recent article has tried to resolve this issue, but I was
not able to locate it.

I am disappointed to hear of the inaccuracy of dendrochronology in the Plains. In Liebmann’s article, the dating of the Big Horn Medicine Wheel of Wyoming has been obtained through dendrochronology. Although methods such as determining chronology by soil deposition, using hydration analysis for flakes found at the site, and attempting to ascertain a date from ethnographic accounts have been attempted, none have provided a reliable date. The only dating method that has worked is that of dendrochronology. The sample was taken from wood found in the western cairn of the wheel and was dated AD 1760. It is unfortunate that inaccuracies of up to 600-850 years have been found. This ambiguity only adds to the uncertainties of the Big Horn Medicine Wheel.

ReplyDeleteLiebmann, Matthew.

2002 Demystifying the Big Horn Medicine Wheel: A Contextual Analysis of Meaning, Symbolism, and Function. The Plains Anthropologist 47: 61-71.