Laid to rest on woven reeds, a bewigged prehistoric boy—or a reasonable facsimile—bears evidence to the Chinchorro's complex mummification rituals. Rather than preserving flesh, the desert people used a paste of manganese-infused ash to sculpt "bodies" atop defleshed skeletons, whose internal organs had been replaced with earth.
Marquet and his team think the start of the Chinchorro's mummification practices coincided with a period of increased rainfall in the nearby Andes mountains (picture) about 7,000 years ago, as evidenced by the discovery of fossils belonging to perennial plants in regions that are so-called absolute desert today.
"That recharged the aquifers and made fresh water available in the lowlands," Marquet said. "It also allowed for more resources in the environment, including more fish, more shellfish, and more seals to hunt." That plenty encouraged population growth, which in turn sparked innovations, Marquet speculated.
To compare Chinchorro population fluctuations with the environmental evidence, Marquet and his team collected data on nearly 500 radiocarbon-dated archaeological sites in southern Peru and northern Chile. The resulting curve indicates that population increased dramatically about 7,000 years ago, peaked about a thousand years later, and began declining by about 5,000 years ago.
(Related: "Rare Mummy Found With Strange Artifacts, Tattoo in Peru.")