You can also read this article in Turkish. Eski Genomlar Down Sendromunun Geçmiş Toplumlarda Varlığını Ortaya Koyuyor
An international research team has examined the DNA samples of nearly 10,000 ancient individuals to identify cases of Down syndrome. Down syndrome is a rare genetic disorder caused by the presence of an extra copy of chromosome 21. Researchers from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig, Germany, found six children with Down syndrome by scanning the genome data. Five of these children were found to have been buried more than 2,000 years ago and lived to be no more than one year old. Despite their short lives, all of these children were found to have been buried with grave goods, indicating that they were valued members of their ancient societies.
Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig have been collecting and studying ancient DNA from humans who lived tens of thousands of years ago for many years. Through the analysis of this data, researchers are able to track the movements and intermixing of humans, and even uncover ancient pathogens that affected their lives. However, a systematic study of genetic conditions with unique characteristics had not been previously conducted. One such condition, Down syndrome, affects approximately one in 1,000 births today.
Surprisingly, Adam "Ben" Rohrlach and his team identified six individuals who harbored an unusually high number of DNA sequences from chromosome 21. This abnormality could only be explained by an extra copy of chromosome 21. One case, discovered in a church cemetery in Finland, was dated to the 17th-18th century. The remaining five individuals were much older: dated between 5,000 and 2,500 BC, they were found in Bronze Age settlements in Greece and Bulgaria, and in Iron Age settlements in Spain. In all cases, the researchers managed to obtain additional information about the graves and remains.
Burials made within cemetery areas and with grave goods
Although today individuals with Down syndrome can typically live long lives with the help of modern medicine, this was not the case in the past. In fact, age estimates from skeletal remains suggest that all but one child only survived to around the age of one. The five burials in Neolithic settlements are located within the settlements themselves and were accompanied in some cases by special objects such as colored bead necklaces, bronze rings, or seashells. "These burial sites seem to show us that these individuals were cared for and valued as members of their ancient communities," says Rohrlach, the study's lead author.
While the research aimed to identify Down syndrome cases, the researchers also discovered an individual with a different condition. Among the approximately 10,000 DNA samples tested, one individual displayed an unexpectedly high amount of ancient DNA sequences from chromosome 18, indicating that they carried three copies of this chromosome. It is known that having three copies of chromosome 18 causes Edwards syndrome, which is associated with more severe health problems than Down syndrome. Edwards syndrome is much rarer than Down syndrome, occurring in less than one in 3,000 births. This finding was also made in one of the Iron Age settlements in Spain, leaving the researchers with a mystery. "We cannot say at the moment why we find so many cases in these locations," says Roberto Risch, an archaeologist at the Universitat Autònoma de Barcelona who works on domestic funerary practices, "but we do know that they were among the few children who had the privilege of being buried inside the houses after their death. This in itself is an indication that they were perceived as special babies."
The authors plan to further expand their research as the number of DNA samples collected from ancient individuals increases in the future. Kay Prüfer, who coordinated the sequencing analysis, says, "What we want to learn is how ancient societies reacted to individuals who may have been in need of help or were slightly different."