When Silvia Bello gives lectures about cannibalism, she starts by asking her audience to imagine a cannibal. “Normally, people think of Hannibal Lecter or something that’s disturbing,” said Dr. Bello, an anthropologist at the Natural History Museum in London.

But archaeological evidence suggests that most cannibalism in human history was not the work of serial killers. Instead, it occurred for complex and varied reasons. Thousands of years ago in Britain, for example, people seem to have eaten their own kind as part of an intricate funeral custom that combined both nutrition and ritual.

At an archaeological site called Gough’s Cave, in southwestern England, human bones that are approximately 15,000 years old bear unmistakable signs of cannibalism, like butchering marks and human tooth imprints that suggest even the ends of toe and rib bones were gnawed to get at every last bit of grease and marrow. But the bones also seem to have been used in cultural traditions. In a paper published in PLOS One on Wednesday, Dr. Bello and her colleagues report what appears to have been a purposeful engraving of a zigzag pattern on a human arm bone, an indication of ritual.