The mummies of ancient Egypt are probably the most widely-recognized examples of humans from old civilizations. Scientists have been working for years to extract DNA from mummies. The mummification process and centuries in the hot, dry desert led to the destruction of mummy genetic material. Exhuming and testing of mummies by archeologists introduced DNA contamination that makes it difficult to pick out the ancient DNA from the residuals left by other humans.
But this year a group of German and Australian scientists isolated and sequenced mummy DNA using new techniques to filter out contamination and amplify the mummies’ delicate genetics. Researchers learned, among other things, that the ancient Egyptians had surprisingly little in common –genetically — with sub-saharan Africans. They isolated DNA from a set of 151 mummified heads found in a burial spot South of Cairo. From the Verge:
The DNA sequencing method used in the study makes the results robust. The researchers looked at any DNA in a given sample, and then isolated the genetic material that might be human. The team then looked for patterns of DNA damage we only see in true ancient DNA, allowing them to ignore the DNA that might be from contamination.
Mitochondria DNA was preserved much more commonly than nuclear DNA. Ninety of the mummies gave up a full sequence of their mitochondrial DNA, but the scientists were only able to sequence the nuclear DNA of three mummies. Mitochondria are parts of the cell that make energy and have their own DNA signatures. A person only inherits mitochondrial DNA from their mother via her egg. Sperm don’t contribute mitochondria during fertilization. Mitochondrial DNA is often used to track human populations through history. Nuclear DNA is what we commonly think of when we talk about sequencing DNA to identify illness, health risks or physical traits of an individual.
Radiocarbon dating showed the age of the heads (youngest to oldest) spanned about 1,500 years, covering a significant chunk of ancient Egyptian history including at least two invasions. Researchers were looking for genetic signatures representing the invasions of Egypt by the Greeks and Romans. Theoretically mummies who died after these invasions might have ancestors from the invading groups. And their DNA would show that. From Science:
[Johannes] Krause, who has studied the DNA of Neandertals, Denisovans, and prehistoric migrants to Europe, recently gravitated toward ancient Egyptian mummies because of the empire’s tumultuous political history. At various points, it was conquered by Assyrians from the Near East, Nubians from farther south along the Nile, Persians, Greeks, and Romans, among others. “Our question was, did those foreign conquests have a genetic impact?” Krause says.
But the mummies DNA showed no signatures from those invading civilizations. That surprised the scientists.
Even more surprisingly, when comparing the mummies’ DNA to modern Egyptians, the scientists found quite a bit of difference. Modern Egyptians have a significant amount — about 20 percent — of DNA traced to sub-saharan African. The mummies had much less — 6 to 15 percent. The ancient Egyptians’ DNA more closely resembled modern day Middle Easterners.
The researchers hypothesized that this difference was probably attributable to the opening of navigation and shipping along the Nile and to the ever-increasing slave trade which peaked in the 19th century. There could, of course, be some sort of confounding factor that separated out this group of mummies from the larger ancient Egyptian population.
This mummy DNA study is the most widely covered since King Tutenkhamun was sequenced in 2014. That study was controversial because of the level of DNA contamination which led some people to allege that King Tut was white or European. The study was also fraught by political changes in the area as the Arab Spring made access to the samples hard to come by. Jo Merchant at Medium:
The team didn’t publish any information on the mummies’ racial or ethnic origins, saying that the data on the issue was incomplete. But that didn’t stop others from speculating. A Swiss genealogy company named IGENEA issued a press release based on a blurry screen-grab from the Discovery documentary. It claimed that the colored peaks on the computer screen proved that Tutankhamun belonged to an ancestral line, or haplogroup, called R1b1a2, that is rare in modern Egypt but common in western Europeans.
But concern over contamination does’t just apply to modern scientists working on the analysis. Rather, the concern is the near century long history of archeologists who’d worked before. From Medium:
Although Gad and his team wore gloves and masks when working on Tutankhamun, no previous archaeologists had done the same — from those unwrapping him in 1925 to those putting him through his CT scan some 80 years later. “You see TV people handling mummies with their bare hands, their sweat dripping on to the mummy,” Tom Gilbert, who heads two research groups at the Center for GeoGenetics, told me.“That’s a classic route of contamination.”
The techniques for the 151-mummy study could potentially be used to re-analyze King Tut and family’s DNA because the technique looks for damage in the DNA before analyzing it. But only if access to the tomb can be granted. That may remain impossible given the current political climate in Egypt. One of the goals of analyzing DNA from ancient peoples is to understand the political relationships of the time. Ironically, access to those is dependent on current political relationships.
Meredith Knight is a frequent contributor to the Genetic Literacy Project and a freelance Science and Health writer based in Austin, Texas. Follow her @meremereknight.