Ever since a British forest guide first stumbled on Roopkund Lake in northern India in 1942, experts have struggled to understand how hundreds of human skeletons ended up in this small, shallow glacial lake, which sits in a valley more than 16,000 feet above sea level.
Over the years, various theories have surfaced to explain who the skeletons might belong to, as well as when and how they made their way into “Skeleton Lake,” as Roopkund is known.
At first, people thought they might be the remains of Japanese soldiers who died crossing through the Himalayas during World War II—but the bones were too old for that. Others suggested a natural disaster, an epidemic of disease or a mass ritual suicide. According to one leading theory, a sudden and severe hailstorm struck a group of unsuspecting pilgrims, sending giant ice balls smashing into their heads and shoulders.
Now, DNA analysis and radiocarbon dating research has upended much of the prevailing wisdom—and raised new questions—about the bones in Roopkund Lake. In a study published in Nature Communications, researchers linked 38 skeletons from the lake to three distinct groups of individuals, including 23 men and women of South Asian ancestry, 14 with genes associated with the eastern Mediterranean region and one individual with Southeast Asian-related DNA.
But DNA isn’t the only thing that separates the groups from each other. While the researchers dated the skeletons with South Asian ancestry to around 800 A.D., the remains of the eastern Mediterranean group and the Southeast Asian individual were much younger, from around 1800. These findings cast doubt on the idea that a single catastrophic event deposited all the skeletons of Roopkund Lake, suggesting they were instead placed there on different occasions, some 1,000 years apart.
Earlier DNA testing of another set of bones from Roopkund Lake indicated the presence of related members of a family or tribe, as well as another group that was smaller in stature. From similar head wounds found on the skeletons, which were all dated to A.D. 850, scientists concluded that a hailstorm had killed the entire group. This theory intriguingly mirrored a local legend, which held that the mountain goddess Nanda Devi had sent a fierce hailstorm to punish a group of pilgrims who had defiled her sacred ground by playing music and dancing.
Researchers in the new study believe a mass death during a religious pilgrimage might well explain the presence of at least some of the skeletons in the first group they identified, of South Asian ancestry. But they have more questions about the second group of individuals, whose DNA indicates they were from the eastern Mediterranean, where Hindu religious practices were not common.
“Whether they were participating in a pilgrimage, or were drawn to Roopkund Lake for other reasons, is a mystery,” the researchers write. Future investigation will focus on archival research, aimed at finding any potential reports of sizable groups of foreign travelers dying in the Himalayas in the past few centuries.
As Roopkund Lake remains frozen for much of the year and is accessible only via an arduous multi-day trek into the Himalayas, scientists believe there could still be many more skeletons yet to be found. As the lake’s fame has grown, however, tourists have been taking bones away as souvenirs, lending increased urgency to efforts to preserve and continue to learn from this remote and mysterious site.