Environmental Science Professor Stephen Macko can tell exactly what you ate just by analyzing a snip of your hair. Not only can Macko tell that you eat bacon for breakfast, but by looking at a mummy's hair, he can help historians and archeologists determine the general diet of an Egyptian who lived 5,000 years ago.
"You can think of your hair as a tape recorder being extruded from your cells," Macko said. "Your breakfast today is your hair a week from now."
Macko has been collaborating with University of Oklahoma Geophysics and Geology Prof. Mike Engel since 1981.
Engel stressed the importance of hair analysis to other fields, such as archeology or anthropology.
This research gives an "alternative way of looking at how ancient human populations were subsisting," he said. In the past, archeologists had to rely on excavation of plants and artifacts found at a site to indirectly determine how people lived in ancient times.
Engel said hair analysis can more directly and accurately determine lifestyles of these people.
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From the excavation of a burial site "you know what [resources were] available, but you have no idea of what the population actually used. Certain subgroups of society might be restricted" from consuming resources, he said. "Through our research, we can directly assess individual diets."
In doing so, Engel and Macko can determine exactly how food resources were distributed within a given population. In fact, with a long enough piece of hair, they can determine how diet varied among seasons and even across years.
In order to determine what a person eats,
Macko isolates organic compounds from the person's hair and uses a mass spectrometer to sort atomic isotopes that make up the compound by weight.
All atoms exist in two or more isotopic forms, each of a different weight. The mass spectrometer uses these small distinctions to differentiate between atoms in different foods and determine what someone has been eating.
Although both professors are proficient in most techniques of geochemistry, each has a specialty. Engel specializes in the isolation of organic compounds while Macko looks at the isotopes in those compounds.
"He isolates them and sends them to me for isotopic analysis," Macko said.
Vegetables, grains, eggs, fish and meats all have different combinations of isotopes. When consumed, these isotopes end up in a person's hair. By looking specifically at the ratios of nitrogen and carbon isotopes in a given hair specimen, Macko can determine what types of food a person has eaten recently. Since hair grows at the rate of about half an inch per month, analysis of a longer piece of hair allows a determination of diet over a longer period of time.
He said this test is a simple and accurate way to verify what people say they have been eating is true.
"We had a volunteer who claimed to be a vegan, but an analysis of her hair indicated isotopes usually only found in meat-eaters. After we showed her the results, she confessed to eating a piece of Virginia ham."
Though the method is not highly disputed, the team still faces difficulties. One of the big challenges with these procedures is making sure samples aren't contaminated.
"It's not that the method is wrong - we have high precision for making measurements," Engel said. "[However,] these materials come out of the ground ... we have to make sure that what's been isolated hasn't been decomposed," he said.
One way Macko and Engel ensure the hair samples are not contaminated is by comparing them to hair from modern day humans. "We know that the distribution [of isotopes] that make up human hair has not changed that much" from mummies to modern humans, Engel said. Researchers can determine the hair signatures of modern vegetarians, vegans, fish and meat-eaters and compare that to the hair signature of a mummy to infer what type of diet the mummy may have had.
From their research, they have uncovered results that have helped anthropologists and historians better understand the past. One of their most controversial results was from an "Ice Man" found mummified in the Italian Alps in 1992. Analysis of his hair suggested he was vegan for the last few months of his life, although researchers found him with what looked to be a bow and arrow.
"There are many theories about the Ice Man's diet," said Macko. "Some archeologists are saying he could have been a shaman, and that his 'weapons' weren't really weapons at all ... Others have suggested that maybe he was just a bad hunter."
Analysis of the Ice Man's teeth showed they were worn down by plant material, corroborating Macko's results. Whatever the explanation, Macko insists that the "data doesn't lie." Any theory about the diet of the Ice Man "has to fit this data."
Macko also has performed hair analysis on other long-dead humans. The Wilton House museum outside Richmond heard about his research and asked him to analyze a lock of George Washington's hair. Washington "was a pretty average guy," Macko said with a smile. Hair analysis indicated that Washington ate a balance of vegetables and meats. "He made a good first leader" because "he was a centrist," Macko added.
Macko and Engel are certainly not planning to slow down the pace of their research any time in the near future. Macko is currently excited about getting a lock of Ramses II's hair. "We have looked at a lot of commoners, but never a pharaoh. It will be interesting to see if his diet was different."
He smiled broadly, excited at the possibility of a new mystery, and once again delivered the line used countless times already in the interview. "After all, you are what you eat."
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