DNA has revealed incest, smallpox and violent deaths among Christians living in caves in medieval Spain. And a Stone Age burial site in France, used for 800 years, is made up almost entirely of men; ancient DNA shows they are heavily related.
In a new study published in the journal Science Advances, researchers sequenced the DNA of a Christian community in medieval Spain that lived in artificial caves carved into the rock. It is one of several medieval cave communities known to have lived on the Iberian Peninsula, including Portugal and Spain. Why these groups chose caves over more traditional village dwellings has long been a subject of debate among archaeologists. While it may be tempting to speculate about hermits or religious groups, there is little evidence to support such theories.
DNA has been able to shed light on the origins of this community, their relationships with each other, and the diseases that afflicted them. The combined information reveals a history of inbreeding, periodic outbreaks of violence, and disease over a period of history. One possibility is that some of the earliest settlers were men with military experience, although it is unclear whether they were professional soldiers or not.
The settlement existed from the mid-sixth century to the eleventh century AD. The early Middle Ages were a dynamic and turbulent era in many parts of Europe, including the Iberian Peninsula. After the fall of the Western Roman Empire in 476 AD, Iberia fell under the rule of the Visigoths, who came from northern Europe.
View of Las Gobas Cave. GPAC, Anders Götherström and Ricardo Rodriguez Varela
The Visigothic kingdom collapsed after being conquered by Muslim armies from North Africa in 711 AD. This event created the territory known as Al-Andalus, which at its largest extent covered most of Iberia. But Christian kingdoms persisted in the north of the peninsula and gradually recaptured territory. What we know about the period in this part of the world is conditioned by events in the major cities of Iberia at the time, such as Toledo, Granada and Cordoba. These were centers of trade, diplomacy and power.
The rural setting of Las Gobas offers a glimpse into life away from urban centres, in one of the distinctive cave communities known from the period. Situated in the province of Burgos, in northern Spain, near the village of Laño, Las Gobas contains a cemetery that was in continuous use from the seventh to the eleventh centuries. It was originally associated with a church, also built in a cave complex. By the tenth century, the inhabitants had moved to a more typical rural village, although the cave church and cemetery remained in use until the eleventh century.
Burials excavated at the Las Gobas site. GPAC, Anders Götherström and Ricardo Rodríguez Varela
Archaeological excavations at the cemetery uncovered the remains of 41 individuals. These remains were subjected to genetic analysis, and 33 of them yielded enough DNA for gender identification (22 males and 11 females). Enough DNA was extracted from 28 remains for further study using various genetic techniques.
The vast majority of the inhabitants were of local Iberian descent, with only a minor contribution from North Africans, despite their proximity to the northern edge of Al-Andalus. This is consistent with historical records indicating limited genetic influence of North African populations in northern Iberia during the Middle Ages. However, some migration did occur, as evidenced by a few individuals with higher North African ancestry after the Muslim conquest.
Two skeletons dating to the early settlement phase showed signs of violence that were likely the result of sword blows to the head. The two individuals were closely related genetically. Surprisingly, one of them survived an injury that had cut through the skull. However, these skeletons predate the Muslim conquest, so their injuries were not caused by conflicts along the Al-Andalus border.
Skulls from Las Gobas with Traces of Violence. Lourdes Herrasti, Anders Götherström
During this period, there was an elevated level of inbreeding, with approximately 61% of the sample with sufficient genomic data for analysis showing signs of inbreeding (14 out of 23). This suggests that the population at this time practiced endogamy – marriage only within the community.
Along with evidence of inbreeding, several of the earliest men were found to be closely related, with only relatively small variations in their Y chromosomes (the packet of genetic material passed down from fathers to sons). This suggests that the site may have been settled in the seventh century AD by a small patrilocal (where couples settle in the husband’s home or community) group that may have had experience of warfare.
The early Las Gobas settlement also contained several cases of the bacterium Erysipelothrix rhusiopathiae, which causes a skin disease in humans. More interestingly, the bacterium often occurs in domestic animals. The bacterium was also present in the late settlement, but at a lower frequency.
Las Gobas Cave in Spain was home to a medieval community. Anders Götherström and Ricardo Rodríguez Varela
The presence of this smallpox-causing bacterium, commonly found in pigs, suggests that keeping these animals was an integral part of the community’s lifestyle. In addition, one of the people infected with E. rhusiopathiae was also a carrier of Yersinia enterocolitica, a bacterium known to infect humans through bad meat or bad water.
Endogamy remained a strong feature throughout the population’s history, even as the community transitioned from cave dwellings to a more typical rural settlement in the tenth century. In this later phase, we found DNA from the variola virus responsible for smallpox in a tenth-century individual.
Some researchers have suggested that smallpox, with its high mortality rate (30% without vaccination), was introduced to Iberia by Muslim conquests. However, the Las Gobas strain of smallpox resembled strains found in Scandinavia, Russia, and Germany during the same period. So it appears that at least one route for the pandemic was from the east.
Increased mobility, exemplified by the growing importance of the northern city of Santiago de Compostela for Christian pilgrims in the ninth and tenth centuries, may even have contributed to the spread of the virus. In all these respects, Las Gobas stands out as a unique site spanning the turbulent period of the early Middle Ages in Iberia.
DNA analysis of skeletons has shown that Stone Age people buried for 800 years in a mass grave in France were mostly from the same male line.
The researchers say the findings highlight the importance of patrilineality in the social structure of these 5,000-year-old communities.
The burial site, located in Aven de la Boucle, a limestone cave in southern France, contained the remains of about 75 people, most of whom were adults when they died. Scientists analyzed the genomes of 37 of the deceased and radiocarbon-dated their bones, which were scattered throughout the site, according to a study published Aug. 28 in the journal Proceedings of the Royal Society B.
The researchers found that people were buried there multiple times between 3600 and 2800 BCE, and that 76% were male. Most of these men belonged to a single paternal line, known as G2, which is passed between males via the Y chromosome.
This discovery suggests that social status may have been passed down through the paternal line, and that the presence of such relationships led to men being more likely than women to be buried at the site.
A mass grave in France was used for centuries by the same group of Stone Age people. Henri Dude
Given that all the men involved in the kinship relationship carry the same haplogroup (G2), this allowed us to hypothesize a patrilineal system, with membership in a particular male line apparently being the predominant factor for access to the collective grave. But this does not explain why several women are buried there.
Perhaps only a limited number of women were allowed or chose to be included in the collective burial. Another possibility is that the bones belonging to women were predominantly removed from the cavity after decomposition and moved elsewhere. As is often the case in prehistoric groups, women often left their clan community to live with their reproductive partner in what is known as a patrilocal residence system. Some females would have preferred to return to be buried in their clan community.
However, it is unclear why this Neolithic group chose this site to bury their dead for such a long period of time. It is possible that the site had some important meaning to them.
The site represented something important to the community, either because of its location, its characteristics, or even perhaps the specific people who were buried there. There could be a thousand different reasons for this choice, and it is highly unlikely that archaeology will ever be able to separate these reasons.
In addition to the skeletal remains, the researchers found numerous artifacts in the cavity, including pottery and objects made from animal bones that may have been used to secure shrouds or clothing.