Imagine a jigsaw puzzle that has no outside edge. Nor is there a picture of the finished product to guide you along.

If you don't die of boredom or slit your wrists in frustration, you may qualify to be an archaeologist. That is just the kind of puzzle archaeologists have been working on for decades.Their puzzle, though, is not a picture stuck to a piece of cardboard. Their puzzle consists of trying to piece together a picture of prehistoric life using a variety of prehistoric clues, such as pollens, dung and charcoal.

Scientists from around the United States gathered in Park City Thursday, Friday and Saturday for the 21st Great Basin Anthropological Conference to share their research and hopefully piece together a better picture of what life in the prehistoric Great Basin was like.

New theories were plentiful, but researchers discovered there are still many more questions than there are answers. And the puzzle is far from complete.

To outside observers, the questions scientists are trying to answer may seem a bit esoteric:

Why was pickle weed processed differently at Danger Cave than nearby Floating Island Cave? Did Great Basin Indians eat the grasshoppers that washed up on the sandy shorelines of the Great Salt Lake? How did antelope hair get into ancient human dung?

And then there's the research by David Rhode, which reveals the presence of pinyon nuts and needles in Danger Cave that date to 7,410 years ago - thousands of years before the pinyon tree was thought to exist in the area.

"I'm amazed by the pinyon remains," said state archaeologist David Madsen. "It presents a real perplexing problem. It's counter to all other botanical evidence in the eastern Great Basin."

Rhode's research now raises questions about how the ancient inhabitants of Danger Cave (a virtual treasure trove of information for scientists) obtained and utilized pinyon trees. Did they wander hundreds of miles to get them?

"We must consider human-assisted migration of the pinyon to this area as well," Rhode said. And there's also the possibility all other previous research is wrong.

Australian H.J. Hall's research into ancient dung reveals the area's prehistoric human inhabitants ate bullrushes, cactus, pine nuts and pickle weed.

Pickle weed also presents a puzzling problem to scientists: Dung analysis reveals the pickle weed was more refined at Danger Cave than at Floating Island Cave.

That could support a theory presented by Madsen that Floating Island Cave was used for seasonal storage and processing, with the ready-to-eat product being transported to their base camp at Danger Cave for winter consumption.

And why eat pickle weed anyway? You only eat pickle weed if there is a "desperate food quest." And there were plenty of other foods available.

But if the inhabitants passed long winters at Danger Cave, the pickle weed may have been a standard dietary staple when other supplies ran low in late winter or early spring, Hall suggested.

Researchers say these studies, as well as dozens of others reported at the conference, all paint an increasingly clear picture of the climate, flora and fauna of prehistoric Utah, as well as man's ability to conform to changing circumstances.

The conference also focused on current research into Fremont Indians, archaic cultures, Paleoindians and more recent Indian cultures of Utah, Nevada and Idaho, as well as discussions on amateur archaeology, vandalism and historical archaeology.