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"Foxtail pines, like other species in section Balfourianae, are very ancient, with very similar fossil species known from Thunder Mountain, Idaho (46 million years), as well as locales in Nevada (42 million years), New Mexico (32 million years), and Colorado (27 million years). During the glacial episodes of the Pleistocene epoch, P. balfouriana expanded its range to lower elevations, and macrofossils of the species have been found as far south as Clear Lake in northern California (Lanner 2007)..." (To read the text at its original source click here  and then scroll down and find it under "Remarks")
Dendrochronology or tree-ring dating was originated by Andrew Ellicott Douglas, the astronomer who established the Laboratory of Tree-Ring Research at the University of Arizona in 1904. Douglas began observing Pinus ponderosa rings. The technique he invented helped him to date the construction of Anasazi ruins. There are two types of a scientific date: absolute (specific to exact calendar years) or relative (younger or older than something else). Dendrochronology or tree-ring dating provides absolute dates both directly and by calibrating radiocarbon results. Radiocarbon dating based on a belief that levels of carbon isotopes never vary is misconception.
Great Basin Bristlecone Pine lives exceptionally long. Utilizing cross-dating method, currently its sequence of still alive and dead wood  extends back for up to 9,000 years providing valuable information to scientists enabling them to count tree-rings with accuracy to date.

Bristlecone Pine dead wood is very important to science. The section in the white rectangle is enlarged on the right. Dendrochronologists left a tag on this long dead tree-remnant to identify the piece. Every single detail of the location is important: altitude, type of substrate, moisture, prevailing winds, etc. (R.V. Byenes)

Researchers used the rings of trees to correct historic dates, to reconstruct past variations in climate and determine changes in the rate of atmospheric carbon-14 production over the past 7,000 years are but a few among many employment fields. For example, it may be used to judge on  musical instruments and art objects, and even in criminology. The pattern of tree-ring on two pine sections of the ladder proved to be a crucial piece of evidence helping to convict the killer of the kidnapped Lindberg baby in 1923. Principles of Dendrochronology and branches of science that uses tree rings as a subject are important in many fields.
Dendrochronology is also used in combination with similar dating techniques utilizing varves (an annual layers of sediment) and ice cores.
Many prominent researchers of the past and present took extraordinaire and unparalleled bristlecone pine as consequential subject for their study. Edmund Schulman, Charles Wesley Ferguson, Harrold C. Fritts, Valmore C. LaMarche Jr., Dana K. Bailey, Darwin Lambert, Ronald M. Lanner, Michael P. Cohen, D. A. Graybill, Tom Harlan, Matthew Salzer, and Malcolm K. Hughes are but a few.
Would you find it interesting to become a dendrochronologist? Build a Tree-Ring Timeline!

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