Mummies and Microbes: A Conversation with Ralph Mitchell

Mitchell’s pure passion for applied microbiology is obvious from the start of our conversation—he seems to be on a mission to convince me of how important these microscopic organisms are.
By Lindsay Bu

When I thank Applied Biology professor Ralph Mitchell for taking the time to speak with me at the beginning of our interview, he laughs and reassures me that he’s not busy at all. I find this hard to believe, as he is currently in the midst of a race to save the world’s oldest mummies.

Mitchell’s pure passion for applied microbiology is obvious from the start of our conversation—he seems to be on a mission to convince me of how important these microscopic organisms are.

“Even though we can’t see them, microbes are central to everything that happens to humans,” he says excitedly. “In fact, without microbes, the world just wouldn’t work.”

Microbiology has always been the fulcrum of Mitchell’s academic and professional career. “I became fascinated with the microbial world very early on,” he explains. As a freshman at Trinity College in Dublin, he enrolled in an introductory microbiology class. “I was just blown away,” he recalls.

Now, he’s at the School of Engineering and Applied Sciences, where he has spent over 40 years teaching and conducting research. Mitchell’s laboratory group engages in the study of microbial processes in natural habitats, specifically the role of microbes in attacking non-living materials. Over the years, he has worked on impressive projects in the field, including analyzing decay processes in King Tutankhamen’s tomb and the Apollo spacesuits.

His latest work involves the study of mummies from the Chinchorro people—hunter-gatherers who lived along the coast of modern day Chile and Peru. These mummies are some of the world’s oldest, dating as far back as 5050 B.C. More than 100 of these Chinchorro mummies are preserved at the University of Tarapacá’s archaeological museum in Arica, Chile. However, in the last decade, Chilean preservationists have been noting the deterioration of the mummies at unprecedented rates.

Mitchell became involved with this project about three years ago. His job is to understand and explain the degradation of these heritage materials.

“When we’re talking about the Atacama Desert in Chile, we’re talking about one of the driest regions of the world,” he explains. “But when the climate started to change and fog began to roll in from the Pacific, the mummies that were preserved there began to go black and turn to jelly.”

Over the past few years, Mitchell’s research group has examined the issue of these rapidly decaying Chinchorro mummies. After receiving pieces of the mummy skin from Chile, the team isolated microorganisms from the skin. They then placed these microorganisms onto pig skin they received from the Harvard Medical School, and exposed the new skin to different conditions, like high humidity and temperature.

Mitchell emphasizes the word “opportunist” in describing microbes and the natural decay process. He explains that, given the proper temperature and right humidity, microbes use the skin as a nutrient source.

“In the case of Chile, climate change is facilitating this decay process,” he says. “With these changing temperatures and conditions, you see the mummy skin begin to deteriorate at an incredible speed.”

According to Mitchell, this is the first time that climate change has become such a pertinent and pressing matter in his field. The effects of changes in weather conditions are becoming increasingly serious in his work on heritage materials. For Mitchell, the need to address this issue is urgent: He contends that the matter will be a long-term project for the international scientific community.

“We’re talking about different countries, different priorities, and different materials that may be at a higher risk of degradation than others,” he says.

While Mitchell says addressing the effects of climate change is daunting in scale, he’s also hopeful that the this issue is going to gain the attention it deserves.

“It’s also very early,” Mitchell says. “Learning to understand and resolve this issue of the way climate change affects heritage materials is clearly going to be a national and international discussion over the next couple of years.”