"Yucatan was a dry place back then. Walking in the dark, they fell into the deep pit, from which there was no exit," Chatters said.
Indeed, Naia's remains show fractures of pubic bones, which are consistent with a fall into a shallow pool from one of the upper passages.
"I think she died almost instantly, if not instantly," Chatters said.
The water level was down in the bottom of the shaft when Naia fell. Then, between 9,700 and 10,200 years ago, global glacier melted enough that rising sea levels submerged everything.
Like Kennewick Man, Naia does not feature the broader and rounder skulls of today's Native Americans. She bore a long and high cranium, a pronounced forehead, a low and flat nose. Her teeth projected outward from her small face.
Such different faces, skulls and teeth have led speculations that prehistoric Americans might represent an earlier migration from Southeast Asia or even Europe via a now submerged land mass where the Bering Sea is now.
But mitochondrial DNA testings -- maternally inherited DNA -- carried out from Naia's upper right third molar suggest a different scenario: Paleoamericans and Native Americans descended from the same land in Beringia.