An expansive analysis of the DNA from ancient remains has revealed cases of Down syndrome from the past — and potentially an archaeological first.

The new study, published this week in the journal Nature Communications, presented the results from nearly 10,000 screenings of ancient remains.

Researchers were searching for the genetic markers of chromosomal mutations, including Down syndrome and a rarer variation known as Edwards syndrome, found on autosomal DNA. They discovered remains of people with “clear genetic evidence” of these conditions were still “buried with care,” which is in line with burial practices for other community members.

Down syndrome occurs when a genetic mutation causes an extra copy of chromosome 21 to form, resulting in physical and developmental changes, the study authors said. Edwards syndrome also comes from a genetic mutation, but it causes three copies of chromosome 18 and more severe outcomes than Down syndrome.

First to ‘reliably’ detect cases

“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,” study author Adam Rohrlach said in the statement.

The research team used a type of statistical analysis, known as the Bayesian approach, to test the autosomal DNA of 9,855 remains spanning millennia across Earth, the study said.

They first used the model to test the 5,000-year-old remains of an infant found in Ireland that was suspected to have Down syndrome, according to the study, and data confirmed the case.

“The statistical model identifies when an individual has approximately 50% too much DNA that comes from one specific chromosome,” study author and lead researcher for the Spanish sites, Patxuka de-Miguel-Ibáñez, said.

After running thousands of DNA samples through the model, they found seven remains that had anomalies, the study said.

“We screened DNA extracted from human remains from the Mesolithic, Neolithic, Bronze and Iron Ages all the way up to the mid-1800’s,” Rohrlach said.

Researchers positively identified six cases of Down syndrome in the ancient remains, and one case of Edwards syndrome, the first identification of its kind, according to the study.

‘Buried with care’

The first case of Down syndrome, a 6-month-old female, lived between 2898 and 2700 B.C. in a province of Southern Bulgaria, the study said. She was found buried in a “ceramic vessel” under the floor of an Early Bronze Age home.

Another baby girl, between 12 and 16 months old, was found buried in a section of yard belonging to a home on the island of Aegina, Greece, and lived between 1398 and 1221 B.C., the study said. She was found with a necklace of beads in many colors and sizes.

Three other babies, who likely died shortly after birth, were found at an Early Iron Age burial site in Navarra, Spain, and lived between 801 and 400 B.C., the study said. They were buried with “rich grave goods, including bronze rings, a Mediterranean seashell, and surrounded by the complete remains of three sheep and/or goats,” researchers said. One infant was found in what appeared to be a decorated fireplace, likely part of a burial ritual.

The last case of Down syndrome was found in a church graveyard in Helsinki, Finland, dating from 1640 to 1790 A.D., researchers said. The remains were discovered in a wooden coffin decorated with bronze pins and flowers.

One case of Edwards syndrome was found in an infant from the Spain site, according to the study.

Researchers noted the burials followed the traditions of their time and the infants were “buried with care.”

“These individuals were buried according to either the standard practices of their time or were in some way treated specially. This indicates that they were acknowledged as members of their community and were not treated differently in death,” Rohrlach said.

The skeletal remains alone were unable to prove whether the infants found in Spain survived childbirth, study author Roberto Risch said, but “they were among the infants buried within homes at the settlement or within other important buildings.”

“We don’t know why this happened, as most people were cremated during this time, but it appears as if they were purposefully choosing these infants for special burials,” Risch said.

Researchers said the rate of Down syndrome cases was much lower than what we see today, but this could be attributed to stillbirths, infants and very young children not being buried and preserved as often as adults in ancient times. Stillborn infants also likely had much more fragile skeletons that might not have survived thousands of years of burial, researchers said.

“As the (autosomal) DNA record continues to grow, genetic disorders with extremely low rates of prevalence will be able to be more frequently discovered,” researchers said. “Integrated with contextual and anthropological data, they afford a perspective into the way that these disorders were viewed and treated in past communities.”

© 2024 McClatchy News
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