New genetic research reveals that excavations in Italy have unearthed the oldest known evidence of father-daughter incest in the archaeological record.
Researchers found genetic clues to this incest in the remains of a teenage boy buried in a Bronze Age cemetery in southern Italy.
The cave ruins of Grotta della Monaca in Calabria, the “toe” of Italy, were used as a burial ground between 1780 BC and 1380 BC. Archaeologists analyzed the DNA of 23 people buried there to understand the population’s genetic background, but they did not expect to find such “extreme parentage.”
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In a study published Monday (December 15) in the journal Communications Biology, a team of researchers outlined genetic findings from the prehistoric Grotta della Monaca.
Even though the skeletons were fragmented and mixed, researchers were able to determine the genetic sex of 10 females and eight males. They also discovered different haplotypes (genetic information inherited from parents) of mitochondrial and Y-chromosome DNA, indicating that this group includes a mix of people from different backgrounds.
While investigating genetic relationships within burial sites, researchers found two cases where first-degree relatives were present, that is, parents and their descendants.
On the surface, this discovery is not particularly noteworthy, since many cultures bury their dead with their biological relatives. In fact, genetic analysis revealed that mother and daughter were buried close to each other at Grotta della Monaca.
However, the case was different for the adult and prepubescent males buried in the Grotta della Monaca cave. The researchers measured a range of homozygous (ROH) segments within the DNA. ROH refers to a mass of similar genetic material that is passed from parent to child. Typically, when humans interbreed outside of their biological families, their genes mix, ultimately resulting in a lower ROH. On the other hand, high ROH correlates with inbreeding.
Most of the people buried at Grotta della Monaca had ROH numbers that suggested their parents were distantly related — possibly within the past six to 10 generations, the researchers wrote. However, this prepubertal male had “the longest sum of ROH segments ever reported in an ancient genomic dataset.”
The researchers wrote that further investigation provided “indisputable evidence that this young man was the offspring of first-degree incest” and clearly showed that he was the son of the adult man buried at the site and his own daughter. However, researchers were unable to find the skeletal remains of the boy’s mother.
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Perhaps due to biological instinct or cultural taboo, humans tend to avoid incest. However, incest has been recorded by archaeologists. For example, Neanderthal genes in the Altai tribe suggested that her parents were half-siblings. Brother-sister marriage was practiced in the ancient Egyptian royal family, and the Stone Age man found in Ireland probably had parents who were brothers and sisters.
However, while these sibling examples are considered second-degree unions, parent-child unions are first-degree unions and tend to be more likely to develop genetic diseases in their offspring. Researchers looked at the boy’s genes to determine if he had a rare genetic disorder, but found nothing.
The discovery that a father and daughter had fathered a son was an “extremely rare and remarkable discovery” and “the earliest confirmed discovery in the archaeological record,” the researchers wrote.
It is currently unknown why the people of Grotta della Monaca behaved in such an unusual manner. This community was not particularly small, and there did not seem to be any class system or system of royal inheritance, where marriages between close relatives helped consolidate wealth and power.
“The parent-offspring reproductive union observed in our study may reflect socially sanctioned behavior,” the researchers wrote. That may explain why the father was the only adult male buried in a cemetery full of women’s and children’s graves.
But we may never know whether the union was acceptable to everyone, whether it was a one-off event, or whether it was the result of coercion or violence.
“This exceptional case may indicate culturally specific behavior in this small community, but its significance ultimately remains unknown,” study co-author Alyssa Mittnik, an archaeogeneticist at Germany’s Max Planck Institute for Evolutionary Anthropology, said in a statement.
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