Bird's attention was caught by stone points and flakes scattered on the surface. What he uncovered beneath was a layered record, each stratum a chapter. The oldest, Layer V, dated to between about 11,000 and 10,080 years before present, held the first people. Above it, the sediments climbed through time toward a youngest layer dated to around 1265 CE and on to the present day. Between occupations, fallen sandstone had sealed sterile bands that neatly separated one era from the next, as if the cave had bookmarked its own history. By the time Bird and later researchers finished, they had catalogued more than five hundred worked implements: scrapers, knives, bolas, bone tools, and the points that would make the site famous.

Fifteen of those tools came from the very bottom layer, and they belonged to a distinctive type: the fluted fishtail point, named for its flared, tail-like base. At Cueva Fell these points lay among the bones of the animals they had killed, extinct horses, giant ground sloths, and guanacos. The discovery was so defining that the earliest culture here is called the Fell tradition, and the cave is its type site. These fishtail points matter beyond their beauty. In North America, the first peoples used the broadly uniform Clovis point across the continent; in South America, communities developed their own fluted variants suited to their own megafauna. The fishtail points are physical proof that the peopling of the Americas was not one tool, one people, but many adaptations spreading into a vast new world.

The people who first sheltered here arrived during a cold, unstable snap, a southern echo of the Younger Dryas, when glaciers advanced and rain lashed the steppe. Far from being defeated by it, they adapted, moving and hunting through a climate that lurched between extremes. Cueva Fell also settled an old scientific question by accident. Its layers showed humans living here before the native horse and the ground sloth went extinct, and the horse bones were the first proof that horses had lived in the Americas long before Europeans reintroduced them. Pollen from the cave revealed grasslands collapsing just before the great animals vanished, an early clue that climate, not only human hunting, drove those extinctions. People were predators here, but so was the Patagonian puma, whose tooth marks scar the same bones.

Cueva Fell represents what researchers call the end of the line, the southernmost reach of humanity's first great journey out of Africa, across Asia, and down the length of two unknown continents. People had arrived at Tierra del Fuego by around 11,000 to 10,500 years ago, so quickly that, to many scientists, the timing alone argues against a slow march down the middle of the Americas and points instead toward earlier coastal routes. Finding sites like this is itself difficult: the ancient population was thin, spread across enormous distances, and the very shelters they used were later dens for carnivores that churned the deposits. That Junius Bird recognized Cueva Fell at all, a faint trace of a vanished world in an immense empty land, makes the discovery as remarkable as what it contained. Today the site, paired with nearby Pali Aike, has been proposed to UNESCO as a World Heritage Site.