The Tiwanaku civilization arose on the wind-swept high plateaus of Bolivia's Altiplano region.
During its height from A.D. 500 to 900, the culture expanded beyond its capital city-state to parts of modern-day Argentina, Chile, and Peru (see South America map).
For reasons not fully understood by scientists, the civilization disappeared before the rise of the Inca and the appearance of Spanish conquistadors.
Some scientists have suggested that a drought in 1200 may have caused the decline. But other experts dispute the theory.
What is not disputed is the rarity of finding a complete skeleton and jewels in the 1,200-year-old pyramid, which experts say has been heavily ransacked by looters.
In the early 1900s railway workers also reportedly used the base of the pyramid as a stone quarry.
"Finding something intact like this is great considering how looted the pyramid is," said Alexei Vranich, a Tiwanaku expert and researcher at the University of Pennsylvania Museum of Archaeology and Anthropology.
But he said the recent finding does little to clear up archaeologists' fuzzy understanding of the pyramid's role in Tiwanaku life.
"In the last year several interesting skeletal finds have come to light, but we're still a bit unclear how the pyramid functioned," he said.
A 2005 study of remains found near the pyramid by John Verano, a forensic anthropologist at Tulane University, supported theories that Akapana was a place of human sacrifice, Vranich said.
(Read related story: "Ancient Peru Torture Deaths: Sacrifices or War Crimes?" [April 29, 2002].)
"Several of the early skeletons found were clearly sacrificed individuals found at the precise location were a shaft of light shines out of a temple doorway on the sunset of the day of the solstice," Vranich said of Verano's work.
(Verano is the recipient of past grants from National Geographic's Committee for Research and Exploration, but the 2005 research was not funded by National Geographic Society.)
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