Scientists to revisit ancient fossils in deep Wyoming pit

CHEY EN NE, W YO. — For the first time in three decades, paleontologists are about to revisit one of North America’s most remarkable troves of ancient fossils: The bones of tens of thousands of animals piled at the bottom of a sinkhole-type cave.

Natural Trap Cave in Wyoming is 25 metres deep and almost impossible to see until you’re standing right next to it. Over tens of thousands of years, many, many animals — including nowextinct mammoths, short-faced bears, American lions and American cheetahs — have missed the four metre opening and plunged to their deaths.

Now, the U.S. Bureau of Land Management is preparing to reopen the opening’s metal grate to offer scientists what may be their best look yet at the critters that roamed the foothills of the Bighorn Mountains during the planet’s last glacial period around 25,000 years ago.

Paleontologist Julie Meachen said she has been getting ready to lead the international team of a dozen researchers and assistants by hitting the climbing gym.

She hasn’t done any real climbing before, she said, and the only way in is to rappel down. The only way out is an eight-storey, single-rope climb all the way back up.

The cave is perpetually cold and clammy, with temperatures about 5 degrees Celsius and humidity around 98 per cent. Even the Bureau of Land Management paleontologist Brent Breithaupt, who isn’t one to fear lots of animal bones, describes the hole as a tad creepy.

“One can only hope that, as a researcher, you’re able to leave,” said Breithaupt, who visited the cave as a college student the last time it was open to scientists. “It’s an imposing hole in the ground. But one that actually has very important scientific value.”

Some mammal remains from the cave could be over 100,000 years old, Breithaupt said.

Exceptionally well preserved, the remote site is far too challenging and dangerous to have been trammelled in by casual spelunkers. The Bureau installed the grate to keep people and animals out in the 1970s.

A mound of dirt and rock containing layer upon layer of animal bones rises from the floor of the 36 metres, bellshaped chamber. Meachen hopes the remains are sufficiently preserved in the cold, sheltered environment to contain snippets of genetic information.

Co-i nvestigator A la n Cooper with the Australian Centre for Ancient DNA at the University of Adelaide will attempt to retrieve fragments of mitochondrial DNA from the bones, Meachen said. Such analysis could show how the animals were related to their modern counterparts and each other and was not possible the last time it was open.

One goal is to learn more about the Pleistocene extinction, which wiped out dozens of species. Proposed causes include climate change and hunting by the first humans to arrive in northern North America.