The Himalayas contain many unique and ancient cultures. Recently, a team of researchers and mountaineers led by archaeologist Dr. Mark Aldenderfer began unraveling mysteries surrounding peoples who lived thousands of years ago in the caves of Nepal's Upper Mustang region.

Aldenderfer led a 20-day expedition to the Upper Mustang to explore mysterious communal graves discovered in the 1990s. The skeletons and burial artifacts were found in caves on the sides of cliffs. To identify possible burial sites, Aldenderfer and his team, including bioarchaeologist Dr. Jackie Eng and seven-time Everest climber Pete Athans, combed the region for deep caves on the brink of collapse. The bones that Aldenderfer's team collected, thought to be the mysterious Membrak people, were then cleaned, pieced together, and analyzed.

This video examines how a scientific team investigates a remote, nearly inaccessible mortuary cave, documents its findings, determines a date for the artifacts, and sketches out a burial site—all without doing any actual excavating.

When the climbers first enter Rhi Rhi cave, they sketch, map, and photograph everything they find in situ (the artifacts' original position). Artifacts include some pottery with daggers embedded, a human mandible, and what looks like a burial pit. The climbers then radio down to Aldenderfer about their findings.

Aldenderfer feels Rhi Rhi and what's inside are so important he should take some risks in the name of science. He prepares to enter the cave himself. Expedition leader and seven-time Everest climber Pete Athans guides him down safely into the cave with a 300-foot rappel.

Aldenderfer climbs into Rhi Rhi's burial hole and lightly investigates its stratigraphy, or layers of debris. This helps him determine that the site is indeed a pit burial with successive layers of human remains, sticks, and rocks.

How can Aldenderfer's team date this cave? They find pottery in the cave that enables them to approximate a date. Dr. Holley Moyes, a ceramics expert, looks at the pottery's style, color, and temper (material added to the clay). She is able to compare the Rhi Rhi pottery with pottery uncovered in a nearby cave in the 1990s. The Rhi Rhi ceramics are identical to the pots found earlier, which range from 1000 BCE to 450 BCE.