Among the dinosaur bones and 4.5-billion-year-old meteorites on the shelves of Stephen Macko’s office are tiny plastic containers that hold hair samples from the likes of Edgar Allan Poe, George Washington, Oetzi the iceman and Diane Sawyer.
An odd assembly, perhaps, but locked within each strand are clues about appetites both ancient and modern. Hair functions as a nuanced physical record of diet over time, “much like a tape recording,” says Macko, a UVA professor of environmental sciences. He applies the tools of organic chemistry to solve mysteries in fields as diverse as anthropology, nutrition and agricultural policy. How did the lifestyles of ancient Egyptian nobility differ from the lower classes? How accurate are the ingredient lists on product labels? Did Poe’s peculiar poetry arise from pollutants in the air he was breathing? Do Americans eat too much corn?
Macko’s ability to answer these questions through isotopic hair analysis has transformed the mild-mannered but puckishly inquisitive scientist into a media darling.
Macko, who pioneered the study of diet from hair, is featured in the recent documentary King Corn, which addresses the prevalence of corn in American agribusiness and diets. The first minutes of the film show the white hallways of Clark Hall, where the film’s two creators, Curt Ellis and Ian Cheney, search for Macko’s lab. Once they arrive, Macko snips a small hair sample from Cheney’s sideburn and runs it through his quarter-million-dollar machine. The process requires that Macko burn the hair samples at 1,000 degrees Celsius, separate the resulting gases with a gas chromatograph, then measure the amount of each isotope in the gases with a mass spectrometer.
The result? An alarmingly high percentage—more than 50 percent—of the filmmakers’ diet derives from corn, a food with little nutritional value.
Since its premiere in 2007, King Corn has provoked curiosity about hair analysis and what it can tell us about what we are made of, both individually and as a culture. Its success prompted Good Morning America to send a sample of Diane Sawyer’s hair to Macko. (She announced the results of his isotopic analysis on air: Fifty percent of the carbon of which Ms. Sawyer is composed comes originally from corn.)
In the film, Macko’s method looks quick and easy. The film doesn’t broach the science that makes this kind of analysis possible; to understand that, one would need a refresher course in chemistry.
Isotopes are a subcategory of elements, like nitrogen or hydrogen. Different isotopes of an element have different numbers of neutrons, which make them slightly heavier or lighter. For example, in the element carbon, its isotopes carbon-12 and carbon-13 have different numbers of neutrons. With a mass spectrometer, one can differentiate the relatively slim carbon-12 from the hulking carbon-13. Everything is composed of isotopes, including our hair, which is made of linked carbon, nitrogen and sulfur isotopes.
Different foods contain distinctive isotopes: meat has more nitrogen-15 than plant material; seafood has higher levels of sulfur-34 than land-based food; and specific grains, like corn, contain a larger percentage of carbon-13 than wheat or rice. Macko can trace isotopes as they travel up through the food chain. If, for example, a cow is fed corn, its meat will contain the isotopic signature of corn, and the human who eats a hamburger made from that meat will as well.
UVA anthropology professor Fred Damon explains why knowing what people eat matters. “We moderns are a little bit exceptional in not thinking we are what we eat and that what we eat places us in social relationships,” he says. “Macko, and that flick King Corn, are not just saying you got your food at Harris Teeter; they are describing an elaborate industrial process and social system draining into our bodies.”
Macko’s first experiments using isotopic hair analysis, in the early 1990s, tracked the eating habits of his students. He wanted to demonstrate to his class how chemistry affects their daily lives. He found a huge variation in the isotopic signatures of his students, especially in concentrations of nitrogen-15. The amount of nitrogen-15 reflects one’s level on the food chain: carnivores contain more of it than omnivores. Predictably, a student athlete who ate mostly hamburgers had a high concentration of nitrogen-15 in his hair, while several vegetarians in the class had much less. A more surprising result was a vegan whose hair had far more nitrogen-15 than would be expected from someone eating so low on the food chain. When she admitted to eating the odd slice of Virginia ham, she confirmed that isotopic hair analysis is indeed a good indicator of diet.
“I coined the term ‘the grocery store diet’ because we have a lot of food choices,” says Macko. “Individual diets can vary a lot due to preference and habit when we are presented with the cornucopia of a grocery store.”
To further test the accuracy of hair analysis, Macko needed to control, or at least observe, the diet of his subjects so that he could more confidently match foods with their isotopic signatures. One of his grad students volunteered to eat only tuna for a week, but Macko declined her offer. Instead, he put his cat, Nutmeg, on a strict regimen of ocean whitefish cat food, then tested tiny amounts of her fur. Unexpectedly, the results showed low levels of sulfur-34, an isotope common in foods originating in a marine environment. Further tests confirmed that the cat food actually contained only 60 percent ocean-based material.
Isotopic evidence can reveal more than the tactics of cat-food manufacturers or the diet choices of college students. It can also illuminate otherwise unknown facets of the lives of ancient peoples. Macko has tested the hair of Chinchorro mummies from the Atacama Desert of Chile, mummies from Egypt’s Middle Kingdom and Egyptian Coptic Christians, as well as the eyebrow hairs of Oetzi the iceman.
“In dry climates, hair from thousands of years ago looks the same as it would if it were cut at a barber shop yesterday,” says Macko. Neither time nor ancient hair dyes such as henna, which was common in Egypt, appear to interfere with isotopic analysis. Adds archaeologist Phillip Trella (Grad ’10): “Hair analysis can tell us a lot about the food-production strategies of the past, and from this information we can infer a lot about ancient societies, things like who traded with whom, how resources were divided. Isotopic evidence gives us information we couldn’t get any other way.”
Macko tested the hair of Chinchorro mummies from several sites, including the seashore—where he found that 95 percent of the inhabitants’ diets was derived from the ocean—to the inland desert, where the diet consisted mostly of grain. But some of the inland mummies showed traces of sulfur-34—marine food in their diet—which suggests that there must have been trading among the disparate populations. Macko tested one mummy, found in the desert, who had hair that matched the isotopic signature found in seashore people. A trader, perhaps? A fisherman selling his wares who died far from home? “Exchanges like these, systems of reciprocity, are the stuff of social systems. The analysis of isotopes may help us to understand how such relationships were built,” explains Damon.
During Egypt’s Middle Kingdom, typically only the wealthy were mummified. “These are the kings and high-priest mummies that you think of with lavish tombs and ancient curses,” says Macko. Hair from these 4,000-year-old mummies is high in nitrogen-15, which suggests that they ate mostly meat. On the other hand, mummies of Egyptian Coptic Christians from the 8th century represent a cross-section of Egyptian society. Macko found that their diets were more varied; they looked much like the diets of modern college students.
“These two groups were living in the same place and had access to similar foods. Possibly the aristocracy ate meat due to the social hierarchy; they had higher status so they ate high on the food chain,” Macko theorizes.
During his research for King Corn, filmmaker Curt Ellis noticed a similar disparity in the diets of Americans. “We’ve made the least healthy foods cheap, so low-income people find themselves eating processed corn products and wealthy people get fresh fruits and vegetables,” he says. “There’s a reason in our culture—unlike in any other time in history—poverty doesn’t go hand-in-hand with hunger, but with obesity.”
In 1991, when Oetzi the iceman was found in a glacier in the Alps, many assumed that he was a hunter who had met an unfortunate demise on a hunting trip around 3300 B.C. He had a bow and arrow and wore clothes made of animal skin. The ice had sheered off Oetzi’s hair, but luckily for Macko a few body hairs were still embedded in the glacier near the body. They revealed that Oetzi had been eating a vegan-like diet in the months before his death. “He wasn’t much of a meat eater, so maybe he wasn’t a hunter. He could have been a shaman, a traveling medicine man. Perhaps he had magic mushrooms in his grass satchel,” says Macko. “His diet likely changed from season to season. Hair grows at about one centimeter per month, and in longer pieces of Oetzi’s hair we would see the change.”
Hair from more recent historical figures is often easier to come by than ancient hair. In the past 300 years, hair was often kept as a remembrance of affection—slipped inside lockets and the envelopes of love letters—or as relics of the dead, like Victorian mourning bracelets. When George Washington died, his family cut locks of his hair and gave them to mourners. Washington’s hair was passed down inside their families and eventually arrived in Macko’s lab at UVA via the Wilton House Museum in Richmond. Washington, it happens, was an omnivore. “I like to say that he had the perfect diet for a first president: he was a centrist,” Macko says.
Edgar Allan Poe’s hair was also saved after his death and Macko tested it after a Baltimore doctor suggested that Poe’s dark literary creations might have been chemically influenced by the pollution of gas lighting in the early 19th century. “There were traces of heavy metals in Poe’s hair, but no evidence of the organic pollutants from the air above that of other people of the time, including his spouse, Virginia,” says Macko.
Inspired by a personal anthropological impulse, Macko tried to test the hair from his daughter’s first haircut. “She was breastfed and I was curious about how isotopes from what her mother was eating would translate into her hair,” he explains. Unfortunately, split ends had damaged the proteins in the infant’s hair. Macko was luckier with hair cut in childhood from the heads of King Corn protagonists Cheney and Ellis; it showed that they had had less corn in their diets as infants than as adults.
After filming was over, Ellis and Cheney tried to eradicate corn from their diets for a month and asked Macko to test them again. “We dropped our numbers significantly—I was down to 39 percent corn from 52 percent, and Ian went from 58 percent down to 44 percent,” says Ellis. “I had to throw out my toothpaste and Ian and I both missed some corn ingredients in things and accidentally had potato chips or gin and tonics.”
The experience of working on King Corn turned Macko into something of a food activist. Now he collects juice bottles and searches their ingredient lists for high fructose corn syrup. “An interest in food and the food industry arises naturally from my work as a scientist who is interested in the natural world. I am deeply concerned with sustainability and thus I am worried about the costs of modern agriculture,” he says. Recently, Macko lectured about the disappearance of ancient populations due to flawed agricultural strategies and land use—and how isotopes can trace the relationships among plants, animals and people who lived thousands of years ago.
Trella, the UVA archaeologist, studies the decline of Upper Mesopotamian city states in the early Bronze Age and uses the clues left by nitrogen-15 to suggest that overproduction of wheat and barley and lack of fertilizer caused crop yields to drop over several hundred years. “There are few universal truths in anthropology, but one of them is that everyone needs to eat,” Trella says. “Eating and producing food is one of the most fundamental ways in which we interact with the environment, which is why it is such a fruitful field for study.”
Hidden among the treasures and the tresses in Macko’s office, there is an ear of corn that was excavated near a Chinchorro mummy in the Atacama Desert. Macko has run pieces of its ancient kernels through the mass spectrometer to double-check that its isotopic signature matches modern corn and the carbon-13 in the mummies’ hair. It is dried out, and some of the white and reddish-brown kernels have fallen off the cob, but it is still recognizable even after thousands of years. “I don’t think it would taste very good,” says Macko. “But if you were to eat it, isotopes that were taken from the soil and the air 3,000 years ago would be in your hair next week, and I could prove it.”
No Shortage of Subjects
In Stephen Macko’s lab, ongoing projects using isotopic analysis involve a range of subjects, from recently unearthed mummies to bald eagles that ranged the U.S. in a previous century.
The mummies are from Peru—the Moche—as well as other locations. The Pre-Incan culture of the Moche flourished in river valley oases along Peru’s northern coast from A.D. 100 to A.D. 800. Recent excavations of burial sites have unearthed mummies from among the elite as well as victims of ritual sacrifice.
Testing isotopes in feathers and bone material from animals helps biologists track populations of fauna over time. “We test the teeth of dead dolphins that wash up on shore, killed as a byproduct of commercial fishing practices,” says Macko. Isotopic signatures help identify where a dolphin lived and ate, so conservationists can identify locations where less-responsible trawler-net fishing occurs. One of Macko’s grad students, Sabrina Foster (Grad ’10), is doing similar work with California sea lions. Another student, Michael Tuite (Grad ’10), is using isotopic analysis of bone to discover causes of mass animal extinctions.
A new project with bald eagles will use as its raw material feathers that date as far back as the early 1800s. Isotopic analysis is expected to illuminate changes in the habitat and diet of this national symbol as America industrialized.
In a recent article in Organic Geochemistry, Macko and an international team published the results of an isotopic analysis of asphalts from archeological sites in Israel suggesting that asphalt was imported from the Dead Sea to the ancient Philistine city of Tel Miqne-Ekron from the 12th to the 7th century B.C. This finding is significant because trade would have had to cross Israelite territory that was hostile to the Philistines in the 12th century. The clash between the Philistines and the Israelites is dramatized in the Bible—in stories about Samson and Delilah and David and Goliath—but Macko’s research suggests that profitable commerce persisted despite ethnic, religious and political conflict.