"Help! Get me out of this tar!" Another mastodon on its way to becoming a fossil.

La Brea Tar Pits

Los Angeles, California

Just east of Beverly Hills lies "L.A.'s oldest tourist trap" -- not a snarky label for the Walk of Fame, but an affectionate term for the La Brea Tar Pits, which have spread the scent of petroleum over this part of California for thousands of years. The pits are celebrated for the now-extinct animals that wandered into them and never wandered out: mammoths, American camels and lions, mastodons, giant ground sloths, and saber-tooth cats. No dinosaurs here -- they'd all died out millions of years earlier -- unless you count the dozens of species of birds that also fell victim to the pits' asphalt glue.

Sentinel lions of the Tar Pits museum.

At La Brea, an underground oil field bubbles asphalt up through cracks in the earth (thanks to California earthquakes). The cracks form depressions where groundwater accumulates and, being lighter than asphalt, floats on the surface. Ice Age animals would come for a drink, step into the pool, get stuck in the hidden goo, and then die, slowly and unpleasantly. "It's kind of sad, not a great way to go, but it makes for a great fossil record," said Dr. Regan Dunn, La Brea's assistant curator and resident paleobotanist.

The La Brea Tar Pits as they appeared over 100 years ago.

Early workers harvest fossils from a pit.

According to Regan, roughly 3.5 million creatures -- everything from megafauna to microscopic insects -- have been hauled out of the pits that cover the 23-acre site. Scientists began digging here in 1913, and they still haven't reached the bottom.

"Every time we dig a hole we find more specimens," said Regan. "We're probably good for the next hundred years."

La Brea's on-site museum opened in 1977, enlightening the public about what it calls the "fossil gumbo" just outside the door. Mounted skeletons and lifelike reproductions of prehistoric pit-victims tower over tourists in several large galleries. One entire wall is filled with nothing but wolf skulls. There's a glassed-in Fossil Lab where people in white coats use tiny toothbrushes and Q-tips to clean 30,000 years worth of crud from recently excavated bones. The "What Is It Like To Be Trapped In Tar" display is a perennial favorite, encouraging visitors to try to pull up plungers encased in the sticky stuff. Only one human has ever been found in the pits; she fell in about 10,000 years ago, said Regan, and she's not on display.

Modern workers clean prehistoric bones in the glass-walled Fossil Lab.

The "What is it Like to be Trapped in Tar?" display.

Outside, a doomed fiberglass mammoth is half-sunk in a greenish pond that steadily bubbles mustard-colored eruptions of methane gas. The asphalt is always rising, and visitors walking from the parking lot have to steer clear of safety cones on the lawn that mark where seepage is coming out of the ground. Flip-flops get stuck and pulled off of feet, said Regan, "and every once in a while we'll have guests come in with kids who have asphalt in their hair."

Museum fresco depicts a typical tar pit day.

Another problem unique to this attraction, said Regan, is the pits' proximity to Hollywood and Disneyland, which convinces some tourists that the fossils are not real and that the people unearthing and cleaning them are actors or animatronic robots. "This the best Ice Age fossil site anywhere in the world, and it's in the middle of Los Angeles," said Regan. "Sometimes it's difficult for visitors to accept that."

Tusked victims of the pits are now museum displays.

Although technically fossils, the bones excavated from the pits are not rock, but actual bones, preserved in asphalt "oil" like sardines in a can. Does that mean, we asked, that ancient DNA could be extracted from them, like in Jurassic Park? "You mean, clone a mammoth?" Regan responded. "We've worked on it for years and haven't been successful -- yet. Maybe with future technologies. It would be supercool."

The idea of reviving long-dead pit megafauna may excite the paleontologists in the Fossil Lab, but bringing back ten-ton Mastodons, or Giant Ice Age Bears, would probably not be great for L.A.'s current human citizens (or tourists). Some of them would blindly flee in terror, and become the latest long-term residents of the tar pits.

Methane bubble bursts the surface of the Lake Pit.