The stillborn baby was likely the grandson of Peder Winstrup, whose well-preserved remains have been the subject of much study

In 1679, prominent Lutheran bishop Peder Winstrup was buried at Sweden’s Lund Cathedral in a coffin containing a tiny bundle. Centuries later, scientists have determined that the hidden package held the remains of a fetus—probably his unborn grandson.

Archaeologists first discovered the stillborn baby, who was delivered prematurely at five or six months gestation, when they X-rayed the coffin’s contents in 2015, reports Jennifer Ouellette for Ars Technica. Now, a DNA analysis published in the Journal of Archaeological Science: Reports suggests that the two were related.

“It was not uncommon for small children to be placed in coffins with adults,” says study co-author Torbjörn Ahlström, a historical osteologist at Lund University, in a statement. “The fetus may have been placed in the coffin after the funeral, when it was in a vaulted tomb in Lund Cathedral and therefore accessible.”

Winstrup was born in Copenhagen in 1605 and became a significant religious leader in Denmark and Sweden. He helped found Lund University in 1666.

Mummified bishop is a unique time capsule from the 17th century

Per Ars Technica, DNA samples from the two bodies found that the fetus was male and that the two shared about 25 percent of their genes. The connection was on the paternal side of the family, pointing to an uncle-nephew, half-sibling, double-cousin or grandparent-grandchild relationship.

Looking at genealogical records, the researchers realized that Winstrup only had one brother, an individual who died childless. That ruled out all possibilities except grandfather-grandchild. Since Winstrup had just one son who survived to adulthood—Peder Pedersen Winstrup—the team concluded that the fetus was most likely his offspring.

Another possibility is that the body belonged to the unborn child of the bishop’s sister, Anna Maria. But because that would only create a match if her husband had specific Y-chromosome characteristics, the team deemed that scenario less likely.

The bishop’s body is one of the best-preserved specimens of human remains from 17th-century Europe. When his coffin was moved to a new site outside of Lund Cathedral in 2012, scientists took the opportunity to study his remains, clothing and other artifacts in the coffin. They discovered that the body was not embalmed, but had been placed on a mattress and pillow stuffed with herbs and hops, which have preservative uses.

The bundle was squeezed under a mattress in the bishop’s coffin. Gunnar Menander

“His remains consтιтute a unique archive of medical history on the living conditions and health of people living in the 1600s,” said Per Karsten, director of the Historical Museum at Lund University, in a 2015 statement.

Additional research on Winstrup’s body published last year analyzed material from a nodule on one of the bishop’s lungs to learn about a strain of tuberculosis he suffered from earlier in life. The work helped corroborate evidence that TB emerged during the Neolithic transition.

Per Science Alert’s Michelle Starr, researchers have occasionally found the remains of children buried in the tombs of unrelated adults at Lund Cathedral. But the surprising discovery of the 74-year-old bishop’s coffin companion could have a different explanation, instead marking the end of a family tragedy.

Winstrup’s son declined to follow in his father’s and grandfather’s footsteps, taking up the study of military fortification rather than religious leadership. He lost the family’s estates during the 1680 Great Reduction, when the Swedish monarchy took the land of many nobles, and ultimately died penniless, without a son to carry on the family name. The researchers suggest that the fetus—the last male Winstrup heir—may have been interred with his grandfather as a symbolic act.