In 2001, archaeologists were painstakingly excavating a dwelling at the Bronze-Age site of Cladh Hallan in the Outer Hebrides islands off of Scotland’s northwestern coast. The house had been oval in shape, with a low door leading to an interior hearth. Other conveniences included sunken storage areas and stone-lined water storage tanks. Under the floors of these houses, though, and under the feet of the occupants, was a fascinating feature that evokes the opening scenes of a classic horror film.

As the archaeologists slowly dug through the floor of the structure, they came unexpectedly upon a human skeleton, legs tucked up in the fetal position. Another skeleton, similarly arranged, was found beneath a different roundhouse’s floor. These people had clearly been laid to rest with care, with stones laid out around them.

When archaeologists began to study the remains, though, they were staggered to learn that each body’s parts had not all come from the same person.…