An international investigation that has analyzed the genome of nearly 10,000 ancient individuals in search of chromosomal trisomies has identified six cases of Down syndrome, all of them in babies: five from between 5,000 and 2,500 years ago and one from a more recent period. Three of the prehistoric cases come from sites of the early Iron Age in Navarra, Spain (2,800-2,500 years ago). In one of these sites, a case of Edwards syndrome has also been found, the first identified in archaeological population. They died before or shortly after birth and were buried inside houses, some with burial goods included, demonstrating that they were valued by their communities.

The study, published in Nature Communications, was led by the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig and involved the participation of the Autonomous University of Barcelona (UAB), the University of Alicante (UA), and the Public University of Navarra (UPNA).

The work is one of the first systematic studies of genetic screening in ancient human samples for rare genetic conditions, such as chromosomal trisomies, characterized by the presence of three copies of a chromosome instead of the usual two. One of these conditions is Down syndrome or trisomy 21, caused by an extra copy of chromosome 21, which occurs in approximately 1 in every 1,000 births. It has been carried out using a new statistical method of genomic sequencing, complemented by an osteological review of the identified cases and existing archaeological records.

Skeleton of a child with Down syndrome who died at around 26 weeks gestational age
Skeleton of a child with Down syndrome who died at around 26 weeks gestational age. Credit: J.L. Larrión / Gobierno de Navarra

Of the five prehistoric individuals with Down syndrome, three belong to the Navarrese sites of Alto de la Cruz and Las Eretas, corresponding to the Iron Age of Navarra, Spain (2,800 to 2,500 years ago), and two date from the Bronze Age (4,700 to 3,300 years ago) from Greece and Bulgaria.

The sixth comes from the cemetery located in a church in Finland dated to the 17th-18th centuries. Additionally, from the Alto de la Cruz site, a case of Edwards syndrome or trisomy 18 has been identified, rarer and more severe than Down syndrome, with an approximate occurrence rate of 1 in every 3,000 births. It is the first of its kind identified in archaeological population worldwide.

According to the analysis of the skeletal remains, all individuals died before or shortly after birth. Only the case from Greece reached one year of age.

Reconstruction of the early Iron Age settlement of Las Eretas, Navarra, Spain
Reconstruction of the early Iron Age settlement of Las Eretas, Navarra, Spain. Credit: Iñaki Diéguez / Javier Armendáriz / Museo Las Eretas, Navarra

One surprising aspect shared by all studied prehistoric cases is that they were buried inside houses, within settlements, some with burial goods, such as the cases from Greece and Bulgaria and a girl with Down syndrome from Alto de la Cruz, who was buried with a rich funerary assemblage (a bronze ring, a seashell, and remains of three ovine or caprine animals), possibly in what was a place of worship. We believe these burials show that these individuals were cared for and valued as part of their ancient societies, says Adam Ben Rohrlach, lead author of the study.

The Iberian communities of the Iron Age had a particular funerary ritual: against the dominant custom, which was cremation, some premature and newborn babies were buried in houses or intramural locations. Nevertheless, the discovery of the four cases with genetic conditions in two nearby and contemporaneous settlements has surprised the research team.

For now, we cannot say what might be the reason, but we know they belonged to the few children who received the privilege of being buried inside the houses after death. This is already an indication that they were perceived as special and valuable babies for the community, but we will need to expand the research with individuals from the same period from other sites to formulate hypotheses about the rituals that may have led to this, explains Roberto Risch, archaeologist from UAB and co-author of the work.

Skeleton of girl with Down syndrome who died at around 28 weeks gestational age
Skeleton of girl with Down syndrome who died at around 28 weeks gestational age. Credit: J.L. Larrión / Gobierno de Navarra

It is possible that only babies who died from natural causes but were perceived by the community as special beings were buried in living spaces, comments Javier Armendáriz, from UPNA. It should be noted, however, that not all newborns buried in Iron Age houses were cases with genetic pathologies. In the Las Eretas settlement, we have found in the same house a boy with Down syndrome and next to him a girl related in the second degree, who could have been his stepsister, adds the researcher.

Regarding the osteological study, the researchers have observed anomalies in some of the individuals, which could be compatible with their genetic condition, without being able to rule out other causes. In any case, these early cases of trisomy in past populations open the possibility of identifying possible osteological modifications related to this genetic anomaly, which would enable their identification in large anthropological collections, says Patxuka de Miguel, osteoarchaeologist from UA.

The authors plan to continue expanding their research in the future as the number of DNA samples from ancient individuals continues to increase. What we would like to know is how ancient societies reacted to individuals who might have needed help or who were simply a little different, says Kay Prüfer, who has coordinated the analysis of the genetic sequences.

Sources

Universitat Autónoma de Barcelona | Rohrlach, A.B., Rivollat, M., de-Miguel-Ibáñez, P. et al. Cases of trisomy 21 and trisomy 18 among historic and prehistoric individuals discovered from ancient DNA. Nat Commun 15, 1294 (2024). doi.org/10.1038/s41467-024-45438-1

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