Was the radiocarbon dating compromised by contamination from old carbon in the groundwater?

These were not hostile questions from people who wanted the discovery to fail.

They were the normal and necessary questions that any extraordinary scientific claim should face.

And the researchers who had made the original claim took those questions seriously enough to go back to Paisley Caves and build an entirely different kind of case.

What followed is a story about how scientific skepticism, applied rigorously, sometimes makes a discovery stronger rather than weaker.

The Caves at the Edge of an Ancient Lake World

The landscape of south-central Oregon today is high desert — a spare, beautiful terrain of sagebrush flats, lava formations, and alkali lake basins that feels remote from almost everything.

Summer temperatures can exceed 100 degrees Fahrenheit.

Winter brings sharp cold.

Rainfall is sparse.

The dominant vegetation is the gray-green shrub carpet of the Great Basin, stretching to the horizon in every direction interrupted only by distant rimrock.

It did not always look this way.

During the late Pleistocene — the period relevant to the Paisley evidence — the northern Great Basin was a fundamentally different landscape.

Pluvial lakes, fed by glacial melt and a wetter climate, filled basins across the region.