By Stephen Caesar
Associates for Biblical Research
One of the most controversial topics in the debate over origins is the age of the Earth.
Geochronology, the science of dating the age of our planet and its major events, is less precise
than most people might believe. One of the most important geological and biological events in
Earth’s history was the massive extinction that ended nearly all life at the end of the Permian
Period and paved the way for the dinosaurs at the dawn of the Triassic Period. The timing of this
event, known as P-T, has been a recent source of heated controversy among geochronologists.
According to the September 17 2004 issue of the journal Science, “A new, apparently
improved, way to date the greatest mass extinction…fails to resolve geochronologists’ longrunning
differences” (Kerr 2004: 1705). The journal reported that
“nailing down the time of the Permian-Triassic (P-T) extinction has revealed
problems in the often competitive business of geochronology. P-T daters must
draw their conclusions from vanishingly small isotopic remains of radioactive
decay. For years, different laboratories using uranium-lead radiometric dating—
the gold standard of geochronology—have been getting entirely different ages for
the P-T extinction” (Ibid).
Roland Mundil of the Berkeley Geochronology Center in California and his colleagues
have used a new method of preparing samples for uranium-lead dating, and have arrived at a date
older than previously thought, but Michael Villeneuve of the Geological Survey of Canada in
Ottawa cautions that “all dates are interpretations….It [i.e., Mundil’s dating method] needs a bit
more proving out” (Ibid).
Indeed, geochronologist Samuel Bowring of the Massachusetts Institute of Technology
analyzed zircons from layers of volcanic ash that were laid down during the P-T event and got a
more recent date. Mundil, however, rejects Bowring’s conclusion. According to the article in
“He thinks Bowring engaged in ‘arbitrary date culling’ by throwing out more than
half his zircon ages before averaging the rest of them together. But Bowring says
his choices were judicious, although ‘necessarily somewhat subjective.’ In some
of his zircons, the two different uranium-lead ratios gave different ages,
suggesting that lead had leaked out of those zircons during the past quarter-billion
years. And other zircon ages looked distinctly old, as if those zircons had
crystallized earlier than the rest and had later gotten mixed in with them….
Bowring believes he can confidently select the reliable zircon ages and discard the
Mundil dismissed this method as “picking and choosing” (Ibid). In response, Bowring
pointed out that two independent studies of the P-T event, one in China and the other in Siberia,
both came up with dates that matched not only each other, but Bowring’s date as well. According
to Science, “Mundil hasn’t explained how subjective interpretation could have produced such a
These controversies demonstrate the inexact nature of the science of geochronology.
Ages that are determined by a certain dating method cannot be held up as incontrovertibly,
irrefutably reliable, at least not until a geochronological method is devised that can be proven
beyond all reasonable doubt to provide scientists with accurate ages of the Earth and its most
significant geological events.
Kerr, R.A. 2004. “In Mass Extinction, Timing Is All.” Science 305, no. 5691.
Stephen Caesar holds his master’s degree in anthropology/archaeology from Harvard. He is a staff member at
Associates for Biblical Research.