Signature of Down Syndrome Found in Ancient Humans

A brilliant and comprehensive new study has analyzed the DNA of almost 10,000 people from ancient and pre-modern societies, and found 6 cases of Down syndrome in past or ancient human populations. One of the specimens dates back as far as 5,500 years ago! They now plan to trace the data to its origins and track these people (mainly children and infants) down to understand the place they held in respective ancient societies, helping us understand how prehistoric societies treated people with Down syndrome and other rare conditions.

DNA Mutations and a Landmark New Statistical Model

One individual from a church graveyard in Finland was dated to the 17th to 18th century, while the remaining five individuals, dating back between 5,000 and 2,500 years before present, were unearthed at Bronze Age sites in Greece and Bulgaria, as well as Iron Age sites in Spain.

In addition to the six newly identified cases, the research team confirmed a previous report of Down syndrome in an infant from Ireland who died between 3629 and 3371 BC.

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Remains of individual "CRU001", a boy who died at or shortly before birth and was buried in Alto de la Cruz. (© Gobierno de Navarra/J.L. Larrion/Max Planck)

For numerous years, researchers at Max Planck Institute for Evolutionary Anthropology (MPI-EVA) have diligently gathered and scrutinized ancient DNA samples from humans who inhabited the Earth tens of thousands of years ago. This thorough analysis has enabled the researchers to track the migrations and intermingling of ancient populations, and notably, to unveil ancient pathogens that impacted their existence. The research has been led by Adam "Ben" Rohrlach and his team, who’ve published their groundbreaking research in the journal Nature Communications.

“Using a new statistical model, we screened the DNA extracted from human remains from the Mesolithic, Neolithic, Bronze and Iron Ages all the way up to the mid-1800s. We identified six cases of Down syndrome. While we expected that people with Down syndrome certainly existed in the past, this is the first time we’ve been able to reliably detect cases in ancient remains, as they can’t be confidently diagnosed by looking at the skeletal remains alone,” explained Dr. Rohrlach, also a statistician at the University of Adelaide.

The typical human genome comprises 46 chromosomes, consisting of 22 pairs of autosomes and either XX or XY sex chromosomes. However, some individuals are born with variations in chromosome numbers, a condition known as aneuploidy.

Down syndrome, for instance, is characterized by an additional copy of chromosome 21. The presence of an additional chromosome leads to the production of extra proteins, which can result in various changes, such as heart defects and learning disabilities. In most instances, individuals with this syndrome exhibit trisomy, where all cells in their body contain three copies of chromosome 21 instead of the usual two. Presently, this condition affects approximately one in every 700 births.

Rohrlach and his colleagues developed a program designed to organize fragments of the retrieved DNA according to chromosomes. This program systematically compared the DNA extracted from each bone to the complete set of samples, enabling it to identify specific bones exhibiting an unusual abundance of sequences originating from particular chromosomes.

“The statistical model identifies when an individual has approximately 50% too much DNA that comes from one specific chromosome,” explained co-author Dr Patxuka de Miguel Ibáñez of the University of Alicante in Spain.

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Aerial view of the Early Iron Age settlement of Alto de la Cruz, Navarra, during the 1989 excavation campaign. (Servicio Patrimonio Histórico Gobierno de Navarra/Max Planck)

Burial Sites and Treatment of Ancient Down Syndrome Infants

The researchers confirmed that all the children had passed away during early infancy, with only one appearing to have reached their first birthday, an expected outcome, considering that Down syndrome is linked to various potential medical complications. The burial sites, more importantly, provided insight into how these children might have been treated by the adults in their community.

The five prehistoric burials were all situated within settlements, indicating a significant aspect of community integration. Some of these burials were accompanied by special items, such as colored bead necklaces, bronze rings, or sea-shells. “These burials seem to show us that these individuals were cared for and appreciated as part of their ancient societies,” says Rohrlach in a statement.

The Finnish burial was from a church graveyard situated in Helsinki, Finland, today a popular tourist destination known as the Helsinki Senate Square. Another individual was unearthed on the Greek island of Aegina, from roughly 3,300 years ago and was interred next to a residential structure, laid to rest with a beautiful bead necklace.

A third individual was discovered at the Bronze Age Bulgarian tell site of Yunatsite, dating back approximately 4,800 years. This infant was laid to rest beneath the floor of a dwelling in what is known as an "urn burial" practice. The remaining three individuals were located in two Iron Age sites in Spain, namely Alto de la Cruz and Las Eretas, dating back roughly 2,500 years ago, reports The New York Times.

Out of the DNA samples examined, one individual exhibited an unexpectedly elevated proportion of DNA sequences from Chromosome 18, indicating that she possessed three copies of this chromosome. This genetic configuration is associated with Edwards syndrome, a condition characterized by more severe health complications compared to Down syndrome. In fact, the mutation usually leads to death before birth – in this case, an unborn fetus, 40 weeks old with severely deformed bones.

"What we would like to learn is how ancient societies reacted to individuals that may have needed a helping hand or were simply a bit different," concluded Kay Prüfer, who coordinated the sequence analysis.

Top image: Modern day woman with Down syndrome looking at you while group of girls practicing yoga in gym. Source: pressmaster/Adobe Stock

By Sahir Pandey