From ars technica: “How humans survived in the barren Atacama Desert 13,000 years ago” Revised for more Optical telescopes

Ars Technica
ars technica

12/28/2016
Annalee Newitz

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The Atacama Desert today is barren, its sands encrusted with salt. And yet there were thriving human settlements there 12,000 years ago.
Vallerio Pilar

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ESO/LaSilla
ESO/LaSilla

ESO/VLT at Cerro Paranal, Chile
ESO/VLT at Cerro Paranal, Chile

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at  Chajnantor plateau, at 5,000 metres
ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

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Cerro Tololo Inter-American Observatory
Blanco 4.0-m Telescope
SOAR 4.1-m Telescope
Gemini South 8.1-m Telescope

When humans first arrived in the Americas, roughly 18,000 to 20,000 years ago, they traveled by boat along the continents’ shorelines. Many settled in coastal regions or along rivers that took them inland from the sea. Some made it all the way down to Chile quite quickly; there’s evidence for a human settlement there from more than 14,000 years ago at a site called Monte Verde. Another settlement called Quebrada Maní, dating back almost 13,000 years, was recently discovered north of Monte Verde in one of the most arid deserts in the world: the Atacama, whose salt-encrusted sands repel even the hardiest of plants. It seemed an impossible place for early humans to settle, but now we understand how they did it.

At a presentation during the American Geophysical Union meeting this month, UC Berkeley environmental science researcher Marco Pfeiffer explained how he and his team investigated the Atacama desert’s deep environmental history. Beneath the desert’s salt crust, they found a buried layer of plant and animal remains between 9,000 and 17,000 years old. There were freshwater plants and mosses, as well as snails and plants that prefer brackish water. Quickly it became obvious this land had not always been desert—what Pfeiffer and his colleagues saw suggested wetlands fed by fresh water.

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Chile’s early archaeological sites, named and dated. The yellow area shows the extension of the Atacama Desert hyperarid core. Also note the surrounding mountains that block many rainy weather systems. Quaternary Science Reviews

But where could this water have come from? The high mountains surrounding the Atacama are a major barrier to weather systems that bring rain, which is partly why the area is lifeless today. Maybe, they reasoned, the water came from the mountains themselves. Based on previous studies, they already knew that rainfall in the area was six times higher than today’s average in that 9,000- to 17,000-years-ago range. So they used a computer model to figure out how all that water would have drained off the mountain peaks to form streams and pools in the Atacama. “We saw that water must have been accumulating,” Pfeiffer said. As a result, the desert bloomed into a marshy ecosystem which could easily have supported a number of human settlements.

Indeed, Pfeiffer says that his team has found evidence of human settlements in Atacama’s surrounding flatlands, which they are still investigating. Now that they understand climate change in the region, Pfeiffer added, it will be easier for archaeologists to account for the oddly large population in the area. The history of humanity in the Americas isn’t just the story of vanished peoples—it’s also the tale of lost ecosystems.

See the full article here .

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