What 4,000-year-old DNA revealed about how ancient societies interacted

Boston Globe

4 days ago

'This finding was quite interesting because we actually know from archaeology that the Egyptian and the eastern-Persian cultures influenced each other for millennia,' Adeline Morez Jacobs, lead author of the new study, said in a media briefing. They shared domesticated animal farming practices and writing systems, for instance.
But we now know that 'below the network of ideas was a complex network of people moving and intermixing with the local population,' said Jacobs, a researcher at Liverpool John Moores University and the Francis Crick Institute.
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While artifacts have provided a general understanding of Egyptian life, genetic analysis has been scarce. One big issue has been heat degrading many DNA samples. Due to poor DNA preservation, only three ancient Egyptian individuals have had their genomes partially sequenced. Those samples were also more recent, dating more than 1,000 years after this one.
Now, with improved technology, scientists were able to analyze the full genome of a man buried in Nuwayrat village, about 165 miles south of Cairo, who was excavated more than 100 years ago and then housed at the World Museum Liverpool. Researchers were able to glean details about life for someone outside of royalty - although a laborer, the man had the more elaborate burial of someone in a higher social class, which probably helped preserve the DNA.
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'It's only over the past 10 to 15 years … we've really learned how to take really minute samples from ancient skeletons [to] maximize our chance of retrieving DNA,' Linus Girdland-Flink, a coauthor and archaeogeneticist at the University of Aberdeen, said in the briefing.
The remains were found in a pottery vessel placed inside a rock-cut tomb (before widespread artificial mummification), which probably kept the DNA unusually well-preserved at a stable temperature. The team analyzed his dental tissue, which locks the teeth into the jaw, a location that is particularly good at preserving DNA.
Radiocarbon dating indicated he probably lived between 2855 and 2570 BC - during an interesting shift in Egyptian history. Upper and Lower Egypt were united a few centuries earlier, followed by a major leap in centralized rule and architecture. The beginning of this golden age of innovation, known as the Old Kingdom, marked notable pyramid construction, including the first step-pyramid complex of King Djoser and the Great Pyramid of Giza.
'This genome allows us, for the first time, to get insights into the genetic ancestry of an ancient Egyptian individual from the Old Kingdom period,' Jacobs said.
The researchers took seven DNA extracts from the man, two of which were preserved well enough to be fully sequenced. They analyzed and compared those samples to a library of 3,233 present-day and 805 ancient individuals.
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The team found 80 percent of the genome was linked to individuals in North Africa, suggesting mainly an emergence from the local population, Jacobs said. The remaining 20 percent of his ancestry could be traced to people in the eastern Fertile Crescent, particularly Mesopotamia (roughly modern-day Iraq).
The findings provide 'genetic evidence that people moved into Egypt and mixed with local populations at this time, which was previously only visible in archaeological [artifacts],' according to a news release from the Francis Crick Institute.
The study focused only on one man, and scientists acknowledged more individual genome sequences would need to be analyzed for a complete picture of Egyptian ancestry at that time
DNA analysis even further back - before the introduction of agriculture in Egypt - could help pinpoint when the ancestry began spreading beyond the local population, said Harald Ringbauer, a population geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, who was not involved in the study.
'That would help resolve whether the Levantine-like ancestry component spread with the adoption of farming - or has deeper roots in North East Africa,' Ringbauer said in an email.
Still, the man who is the focus of the study is intriguing on his own. Analyzing the skeleton, the researchers could tell he lived to a relatively old age for that time - potentially in his mid-60s. That would be the equivalent of someone living into their 80s today, said coauthor Joel Irish.
Features on his skull and pelvis indicated arthritis and a high degree of osteoporosis in his bones. From the back of his skull and vertebrae, the researchers determined that he looked down and leaned forward a lot in his lifetime. Muscle markings on his arms and shoulders show that he was holding his arms in front of him for long periods of time, along with evidence of squatting on his ankles - probably placing him as a potter.
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But his burial would be unusual for a potter. This manner - in the rock-cut tomb and a large pottery vessel - is typically reserved for someone in the upper class.
'That's interesting because it's also at odds with the fact that he had an incredibly hard physical life,' Irish, a dental anthropologist at Liverpool John Moores University, said in the briefing.
Other researchers said the findings were a significant step forward in ancient-DNA analysis and our understanding of Egyptian history.
For instance, royal dynasties were shown to have rather limited gene pools because of their high inbreeding, said Yehia Gad, emeritus professor of molecular genetics at National Research Center in Egypt, who was not involved in the research.