Benfer speculates that the sculpture represents Pacha Mamma, the most important god of the Andes. He acknowledges the difficulty of proving that, however, because the next known sculpture of the mother goddess does not appear until 800 BC.
"The disk would frown over the sunset on the winter solstice, the last day of harvest," Benfer said.
Alignments in the temple also pointed to the position at the summer solstice of a constellation known in Andean culture as the fox, Benfer said.
Unlike Western constellations, which are outlined by groupings of stars, some Andean constellations were made from dark areas in the sky that are gaps in the bright Milky Way.
Scientists once thought that the gaps represented a lack of stars, but astronomers now know that they are caused by large clouds of dust that block light from distant stars.
The so-called dark cloud constellation of the fox is well-known today in the region, but archeoastronomer Anthony Aveni of Colgate University doubted that it has maintained its shape for four millenniums.
"He has an alignment. That's neat," Aveni said. But the idea that the ancients were looking at the same constellation "is a bit of a leap for me."
Last summer, Benfer's team also partially excavated a second sculpture, that of a life-sized human figure playing a pipe. The figure is sitting with its legs sculpted in high relief and hanging over the edge of one of a series of short platforms that lead down to what appears to be another temple.
The remaining 18 acres of the site have a variety of buildings, most of them from later cultures, that include a ceremonial center, stepped pyramids and what apparently was a residence center for elites. Most of those have been looted.
Oval houses that probably served as homes for families of commoners sit across a ravine from the main pyramid.
There were probably other buildings farther down the slopes, Benfer said, "but the Chillon River removes everything from time to time."
Evidence of pottery indicates that the site was inhabited for centuries, but it is not yet clear whether or how it was eventually abandoned.
"There were people in the valley at the time of the Spanish Conquest, but they were of several ethnic groups," Benfer said.
That suggests that the sophisticated civilization was eventually replaced by small bands of farmers who immigrated from various areas.