It’s easy enough to imagine why 19th-century botanist William Jameson believed the dense forests of Ecuador’s Quijos Valley had to be devoid of human life. Forming a natural corridor between the Andes Mountains and the Amazon River, the valley’s montane rainforest features a pristine landscape distinguished by its persistent low-level cloud cover and an abundance of moss sprawled across tree trunks and branches.

But 300 years before Jameson’s arrival, an estimated 35,000 indigenous Quijos lived in the valley, building agricultural settlements, conducting trade and maintaining independence from the region’s dominant Inca population. Then, in the 1580s, these indigenous populations vanished, decimated by the arrival of Spanish explorers and the bevy of disease and violence that accompanied them. The Quijos people left little evidence of their civilization behind, paving the way for Jameson and later arrivals to discount their existence. Now, thanks to a new study published in Nature Ecology and Evolution, their story is finally being told.

National Geographic’s Alejandra Borunda reports that researchers from the Open University in Milton Keynes, England, used 1,000 years’ worth of built-up sediment found at the bottom of the valley’s Lake Huilla to create a timeline of the area’s population—and depopulation.

The oldest layers revealed pollen from maize and other crops grown in the region, as well as traces of charcoal that suggest the indigenous groups lit fires to clear fields, cook and bake pottery, Ars Technica’s Kiona N. Smith notes. It’s unclear when the Quijos first developed agriculture, but the sediment finds indicate the valley was inhabited by pre-Hispanic groups for more than 500 years.

The next phase in the sediment timeline marks the arrival of the Europeans, presenting a geological record of catastrophe. According to the study, Spanish colonizers established the town of Baeza alongside the Quijos settlement of Hatunquijos in 1559. By 1577, indigenous groups had either fallen victim to Spanish brutality or dispersed throughout the region, fleeing from their oppressors to leave just 11,400—down from a 1541 population of 35,000—concentrated around Baeza.

Around that same time, the Quijos, devastated by disease and forced labor, staged a series of uprisings against the Spanish. The high level of charcoal found in sediment cores dating to about 1588 point to the outcome of these rebellions, which resulted in the fiery destruction of two nearby settlements and both the Spaniards’ and natives’ abandonment of the valley. By the mid-1800s, all that remained of Baeza was three isolated huts.

According to BBC News’ Mary Halton, a subsequent increase in grass pollen shows the forest’s reclamation of the valley after centuries of conflict and agricultural field-clearing. By 1857, the year Jameson explored the area, it had been repopulated not by humans, but the many plant and animal species that inhabited the Quijos Valley prior to humankind’s arrival some 40,000 years earlier.

Jameson was mistaken in his description of the Quijos’ untouched majesty, which he imagined “since creation, [had] remained unpeopled by the human race.” His account does, however, offer compelling evidence for nature’s hold over land monopolized by humans. Still, the study notes, humans were quick to alter the valley once more, returning in the 1800s with agricultural settlements and herds of large grazing animals. Although these smaller groups had less of a lasting influence on the valley than their pre-Hispanic counterparts, “even the impact of low human populations drives changes in cloud forest vegetation composition and structure,” the authors write.

The Quijo Valley findings have a plethora of implications, some positive and others not. The revitalization of the region after the 16th century suggests forests are capable of recovering from human-inflicted damage; the speed and scale of the Quijos’ disappearance speaks to the unexplored long-term ecological consequences of European contact.