Around 100 prehistoric "cult sites," with stone representations of male and female genitalia, have been discovered in an extremely dry region of Israel's Negev Desert.

The sites in the Eilat Mountains, dating to 8,000 years ago, feature penis-like structures of stone structures and artifacts with vulva shapes cut into them, researchers say.

In one place 44 separate cult sites were found within an area of less than 200 acres, the research team reported in an article in the Journal of the Israel Prehistoric Society.

"Taking in[to] consideration the topography, environmental conditions and the small number of known Neolithic habitations in the general southern Negev, the density of cult sites in this region is phenomenal," the researchers wrote.

At many of the sites, stone circles between 5 to 8 feet across were found with penis-shaped stone installations pointing toward them, along with standing stones almost 3 feet high, stone bowls and carvings of human-like shapes.

"The circle is a female symbol, and the elongated cell is a male one (phallus)," says Uzi Avner, a researcher with the Arava-Dead Sea Science Center and the Arava Institute.

Although apparently used for ritual activities, archaeologists have been unable to determine exactly what those rituals might have included, although bones uncovered at the sites suggest animal sacrifices may have been involved.

The arrangement of the stones at the sites suggests not only fertility but also death, the researchers suggest, "signified by the burial of stone objects and by setting them upside down."

The combination of representations of death and fertility together is common in many cultures, they say.

"Combinations of both are actually well-known in anthropological studies as relating to ancestral cult," they wrote in their published study.

Although the sites are in a region that receives less than an inch of rain annually, it could have been wetter 8,000 year ago -- but not much, Avner says.

"The climate of the 7th-6th millennia B.C. was a little moister than that of the present, 40 percent to 20 percent more rainfall, but the desert was [still] a desert," he says.

There are probably many more such cult sites in the surrounding region, the researchers say.

"The number of cult sites recorded to date suggests that many more still await discovery," they wrote. "Many more may be found on the mountains of the Negev, southern Jordan and Sinai."