http://www.berkeley.edu/.../releases/2003/06/11_idaltu.shtml
quote:
BERKELEY - The fossilized skulls of two adults and one child discovered in the Afar region of eastern Ethiopia have been dated at 160,000 years, making them the oldest known fossils of modern humans, or Homo sapiens.
...
The sediments and volcanic rock in which the fossils were found were dated at between 160,000 and 154,000 years by a combination of two methods. The argon/argon method was used by colleagues in the Berkeley Geochronology Center, led by Paul R. Renne, a UC Berkeley adjunct professor of geology. WoldeGabriel of Los Alamos National Laboratory and Bill Hart of Miami University in Ohio used the chemistry of the volcanic layers to correlate the dated layers.
And that doesn't even begin to touch the age of ancestor species of hominids.
Note that 14C was not used, but two independent methods, one radiometric and one chemical, and the dates of the two methods agreed.
My interpretation of this is that the dating was done with the argon/argon method at two or more locations and/or two different horizons (of, I presume, volcanics). It is unclear if the 160,000 and 154,000 dates are of two bracketing horizons, or if it is an error range of a date of a single horizon.
The chemical analysis of the volcanics was to correlated the volcanic horizon at one location to that of another location - In other words, to confirm they were the same horizon/layer. But this chemical analysis was not a dating methodology in itself.
Moose
Professor, geology, Whatsamatta U
Evolution - Changes in the environment, caused by the interactions of the components of the environment.
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