The basin, which has no outlet to the sea (it is what geologists call a closed basin, where water that flows in has nowhere to go except evaporation), accumulated water over time into a substantial lake.

That lake is called Lake Otero by geologists and researchers.

At its maximum extent, it covered much of the central Tularosa Basin — a body of water potentially hundreds of square miles in area, relatively shallow but persistent, fed by runoff from the surrounding mountains and maintained by the cooler, wetter conditions of the glacial period.

It supported aquatic plants, fish, and the kinds of ecological communities that productive shallow lakes in arid regions develop when conditions allow.

Around its margins grew the vegetation that shallow lake shores produce: reeds, aquatic grasses, the bushy aquatic plant called Ruppia cirrhosa — sometimes called widgeon grass — that grows in brackish and saline water and would later become centrally important to the dating controversy.

The lake margins were also, by every indication that has emerged from decades of research in the basin, a place where people lived, traveled, and left behind the marks of their passing.