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C. Successfully Tracking Our History

Narrator: This is Science Today. A geologic dating method called the argon-argon technique recently passed an important reliability test. According to University of California, Berkeley geologist, Paul Renne, this means geologists will be more confident in dating events that occurred hundreds of million of years ago.

Renne: This method could become absolutely the most powerful dating method for all of geologic time. Right now, it clearly is for the young end of the time scale. But there are other methods that are more accurate for older times, so this is going to have implications over the whole range of geologic time over the past four and a half billion years.

Narrator: Renne says this method can also be used where there is no historical record.

Renne: For example, the peopling of the New World from the Bering Straits down through the Americas we know occurred by at least 13 thousand years ago, but none of the peoples that evolved as a result of those migrations had a recorded language. So we wanted to be able to expand the horizons of this method.

Narrator: For Science Today, I'm Larissa Branin.