The Mummy Unwrapped: Looking for Genetic Clues in Ancient DNA

By Jeanette McCarthy, MPH, PhD

Modern technology such as X-rays and CT scans have allowed scientists to perform a "virtual unwrapping" of our ancient Egyptian ancestors. Courtesy of SGI and the British Museum

I just returned from London, where I took my kids to the British Museum. The last time I visited was about 14 years ago, and I couldn’t help but marvel at how much has changed, including how technology is being used to teach museum visitors about our ancient ancestors. In the exhibit Mummy: The Inside Story, we learned how scientists have used CT scanning as a noninvasive means to look into unopened mummy cases and reveal the secrets within. They found a male buried in a case depicting a female; a broken tool used for extracting the brain left in a nasal passage; stuffing placed under the bandages in the thighs and chest of a mummy, presumably to portray a rare overweight Egyptian; and serious dental problems in many of the mummies. As awe-inspiring as it was, I couldn’t help wondering why we haven’t yet analyzed their DNA!

As it turns out, routine DNA testing of mummies is still under development and was really only made possible with the latest next-generation sequencing technology. Testing has been carried out on ancient human remains, such as Cheddar Man, dating from about 7,000 years ago in England, a Denisovan girl from Siberia 40,000 years ago, and others. But these remains had been preserved by freezing. Mummies have been exposed to intense heat, which degrades DNA, and an embalming process. Last year, German researchers reported preliminary findings that small quantities of human DNA can be preserved in mummies and are in the process of sequencing five mummies.

In the meantime, what have we learned from sequencing other ancient human remains? Evidence suggests that modern human ancestors mated not only with Neanderthals, but also with Denisovans in the Paleolithic age (some 40,000 years ago). Denisovans inhabited Siberia to Southeast Asia and represent a distinct lineage, a sister group to Neanderthals, whose migration out of Africa preceded our own. A paper published just this month reports that this interbreeding with Denisovans may have conferred an advantage to modern humans. Tibetans carry a variant form of a gene that appears to have allowed them to adapt to living at high altitudes. This gene variant is not found in other parts of the world, but it is found in Denisovans, suggesting that they contributed it to the gene pool of modern Tibetans!

Visiting the British Museum, I was reminded how old human history is, how exciting it is to discover evidence of these ancient humans, and how fortunate we are to live in a time when we have the tools to study their genetic makeup. Why did modern humans survive while these ancient lineages died off? Did genetic changes leading to brain development or some other physical attributes contribute? And, if so, which ones? Advances in DNA sequencing technology will help answer these and other questions in the coming years. Hopefully, by the next time I visit the British Museum, we will have a complete genetic profile of those amazing mummies.