A day’s work for Colorado State anthropologist Diane Waddle can include encounters with deadly cobras, excavations on steep walls using rock-climbing equipment and traveling to fossil sites on roads so rough a kidney belt is required.
But the treacherous conditions are worth the bounty Waddle and two other anthropologists recently uncovered in a remote limestone cave in Botswana, Africa: fossilized bones of thousands of tiny bats, shrews, birds and frogs as well as a complete skull of an adult primate and the jawbone of a juvenile primate believed to be ancient ancestors of present-day baboons.
The vast collection of fossils is one of the few uncovered in Botswana and contains well-preserved specimens of small mammals that may have roamed the earth sometime between 100,000 and 3 million years ago. Most likely used by owls and other mammals to eat their prey, the cave is so rich with fossils it’s called Bone Cave.
Waddle and the other researchers believe the find can help fill the gap in the fossil record of Botswana, an area that has not been a major focus for anthropologists or archaeologists in recent years. Although there are numerous sites containing stone tools in Botswana, the only human or primate remains from Botswana are less than 10,000 years old and are fully modern. Other fossils found in Botswana have been from the Middle Stone Age, roughly 100,000 years and earlier.
"This is a great find because of the wealth of fossils in the cave," Waddle said. "It’s particularly important because Botswana has virtually no fossil sites of this kind and there really is no fossil record of primates at all. Many fossil sites may only produce a few fossils.
"This is really impressive because it’s like a big pile of bones glued together."
Waddle said the main reason that not much is known about the evolutionary history of this region is the remote location of the caves; about an 11-hour drive from the nearest town. To get to Bone Cave, the research team must rely on tire tracks from the previous year’s expedition, which often proves difficult. The rainy season causes grasses to grow over the tracks and elephants scar the road with footprints.
Using a grant from the National Geographic Society, Waddle began making the trips to Bone Cave with anthropologists Callum Ross of SUNY Stoney Brook University and Blythe Williams of Duke University in 1994. Colorado State anthropology students Jodi Laumer and Lawrence Steumke traveled to Africa with the team on the most recent trip.
In the project’s first two years, researchers took an inventory of the cave and learned how to better navigate its narrow passages, which serve as a link between two chambers where the fossils are located. To get to the main chamber–called the Drop Room–the research team must climb down a steep rubble slope to a small opening measuring 4 feet across. The larger primate bones are embedded in the steep rock walls and ceilings of the Drop Room, making the fossils much more difficult to reach and remove. To access these fossils, the research team dangles in harnesses and other rock-climbing equipment as high as 15 feet above the cave floor, carrying drills and other excavation tools.
The main chamber below the Drop Room, known as the atrium, consists of spectacular stalactite formations. The atrium’s ceiling is covered with a rock matrix containing the bones of small mammals.
To access the second chamber, Waddle and the others must pass through a gauntlet of bats, bugs and critters, including snakes.
During their most recent trip, Waddle and the other members of the research team encountered a 5-foot long cobra inside the cave. The team quickly crawled out of the cave to safety while Ross drove to the nearest town six hours away to retrieve a shotgun. Because he was the best shot of all the researchers in the party, Steumke was charged with entering the cave and shooting the snake. To celebrate restored peace, each member of the research team ate a piece of the cobra, cooked to perfection on an open fire.
"No one wanted to go back into that cave until we knew that cobra was dead," Waddle joked.
Waddle will spend the next several months in the safety of her lab at Colorado State separating the hard breccia from the primate skull and other large bones taken from the site. The technique involves coating exposed bone with a preservative and soaking the specimens for several weeks in vinegar or other weak acid to dissolve the calcium carbonates that hold the breccia together. Once the specimens are restored, Waddle will take them to the Smithsonian Institution in Washington, D.C., for identification, using its inventory of primate fossils to determine whether they represent a new or existing species.
Portions of rock retrieved from the cave where the largest bones were found will be sent to laboratories at the University of Georgia for dating.