DNA reveals inbreeding, smallpox and violent ends among cave-dwelling Christians in medieval Spain

In a new study, we have sequenced DNA from a Christian community in medieval Spain that lived in artificial caves carved into a rocky outcrop.

This is one of several medieval cave communities known to have lived on the Iberian peninsula – which includes both Portugal and Spain. Why these groups favored caves over more conventional village dwellings is a subject of longstanding debate for archaeologists. While it may be tempting to speculate about hermits or religious groups, there’s scant evidence to support such theories.

Our study, published in Science Advances, explores the possibilities, adding genetic analysis to what we know about the physical remains of people from the site’s cemetery. DNA was able to shed light on the ancestry of this community, their relationships to each other and the diseases that afflicted them.

The combined information reveals a story of inbreeding, occasional bouts of violence and disease during a fascinating period in History. One possibility is that some of the earliest settlers were people with Military experience, though it’s unclear whether they were professional soldiers or not.

The settlement existed from the mid-sixth century to the 11th century A.D. The early middle ages was a dynamic and tumultuous era in many parts of Europe, including the Iberian peninsula. After the fall of the western Roman empire in A.D. 476, Iberia came under the rule of the Visigoths, who came from northern Europe.

The Visigothic kingdom collapsed following a conquest by Muslim armies crossing from North Africa in A.D. 711. This event established a territory known as Al-Andalus which, at its greatest extent, covered much of Iberia. But Christian kingdoms persisted in the north of the peninsula and gradually reclaimed territory.

Related: Vast Goth cemetery brimming with grave goods and ornate silver jewelry discovered in Poland