### DNA Uncovers Mysteries of a Medieval Cave-Dwelling Community in Spain
In a pioneering study published in *Science Advances*, scientists have sequenced the DNA from a medieval Christian community that resided in man-made caves hewn into a rocky formation in northern Spain. This community, situated at the Las Gobas site in Burgos province, presents a rare insight into the lives of individuals who opted to dwell in caves instead of traditional village homes during a volatile and transformative era in European history.
#### The Mysterious Cave-Dwelling Societies of Iberia
The Iberian Peninsula, encompassing present-day Spain and Portugal, hosts several recognized medieval cave communities. These groups have fascinated archaeologists for years, who have speculated about their preference for caves over more standard village environments. While some have conjectured that these communities consisted of recluses or religious sects, there has been scant evidence to substantiate such claims—until now.
The Las Gobas location, close to the village of Laño, was inhabited from the mid-sixth century to the 11th century CE. The early Middle Ages marked a time of considerable turmoil in Europe, especially in Iberia. Following the collapse of the Western Roman Empire in 476 CE, the region fell under the sway of the Visigoths, a Germanic tribe that had migrated southward. However, the Visigothic realm disintegrated after the Muslim invasion of Iberia in 711 CE, resulting in the formation of Al-Andalus, a Muslim-governed region encompassing much of the peninsula.
Even with Al-Andalus’s prominence in the south, Christian kingdoms endured in the north and gradually began to recapture territory—a movement referred to as the Reconquista. The Las Gobas site provides a distinct viewpoint on life in rural Iberia during this time, far removed from major urban centers like Toledo, Granada, and Cordoba, which served as focal points for trade, diplomacy, and authority.
#### Insights from Archaeology and Genetics
The Las Gobas site features a cemetery that was in continuous use from the seventh to the 11th century. Initially associated with a church located within the cave system, by the 10th century, the residents had relocated to a more traditional rural village, yet the cave church and cemetery remained active until the 11th century.
Excavations at the cemetery revealed the remains of 41 individuals, with genetic testing conducted on 39 of them. Among these, 33 provided sufficient DNA for sex determination (22 males and 11 females), while 28 had enough DNA for further analysis employing various genetic methodologies.
The genetic testing showed that the inhabitants of Las Gobas were primarily of local Iberian descent, with slight genetic input from North African groups, despite the site’s closeness to the northern boundary of Al-Andalus. This outcome is consistent with historical documents indicating minimal genetic impact from North African groups in northern Iberia during the Middle Ages. Nevertheless, some migration did take place, as shown by several individuals who exhibited elevated North African ancestry following the Muslim incursion.
#### Evidence of Violence, Inbreeding, and Illness
The research also revealed indications of violence and inbreeding within the community. Two skeletons dating back to the early days of settlement displayed evidence of violence, likely from blows inflicted by swords. These individuals were closely genetically related, and one of them had survived a grievous injury that penetrated the skull. Importantly, these injuries were sustained before the arrival of Muslims, hinting that they did not stem from conflicts along the borders of Al-Andalus.
The genetic study further indicated notable levels of inbreeding in the community. Approximately 61 percent of the sample with adequate genomic data available showed signs of inbreeding (14 out of 23 individuals). This suggests that the population engaged in endogamy—marrying solely within the community. The slight variations noted in the Y-chromosome among the earliest males imply that the site might have been inhabited by a small patrilocal group (where couples reside in the husband’s home or community) potentially experienced in warfare.
In addition to signs of violence and inbreeding, the research identified instances of disease within the community. Several individuals from the initial settlement phase were found to be infected with the bacterium *Erysipelothrix rhusiopathiae*, responsible for a skin disease in humans, commonly affecting domesticated animals, especially pigs. This finding implies that livestock rearing played a vital role in the community’s way of life.
Moreover, one individual was discovered carrying both *E. rhusiopathiae* and *Yersinia enterocolitica*, a bacterium that infects humans via contaminated food or water. In the later phases of settlement, researchers identified DNA from the variola virus, which causes smallpox, in a 10th-century individual. Interestingly, the smallpox strain found in Las Gobas was similar to those recorded in Scandinavia, Russia, and Germany during the same timeframe, implying
