Richard Dawkins & Lalla Ward reading from Chapter 4 "Silence and Slow Time" of Dawkins' 2009 book "The Greatest Show on Earth: The Evidence for Evolution". Dawkins describes Dendrochronology, or treering dating, which is the scientific method of dating based on the analysis of patterns of treerings.

Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year. This has three main areas of application: paleoecology, where it is used to determine certain aspects of past ecologies (most prominently climate); archaeology, where it is used to date old buildings, etc.; and radiocarbon dating, where it is used to calibrate radiocarbon ages.

In some areas of the world, it is possible to date wood back a few thousand years, or even many thousands. In most areas, however, wood can only be dated back several hundred years, if at all. Currently, the maximum for fully anchored chronologies is a little over 11,000 years from present.

Image links:
1: http://creativebits.org/files/leopard...
2: http://globecanada.ca/english/activit...
3: http://uts.cc.utexas.edu/~wd/courses/...

Amazon Book link: http://www.amazon.com/gp/product/1416...

Wiki Dendrochronology: http://en.wikipedia.org/wiki/Dendroch...