Mary Eubanks. Les Todd
Mary Eubanks. Les Todd

The Accidental Scientist

A biologist began studying ancient Mexican pottery and ended up making genetic discoveries that could help feed the world.
June 1, 2006
 

The same merciless sun that blasted a drought-stricken North Carolina in the summer of 2002 shone like a spotlight of triumph on Mary Eubanks. The scientist says she felt vindicated, exultant even, as she gently pushed her way through the lush green foliage of thriving corn plants festooned with fat ears of corn that hung over her head. The plants had sprung from the same desiccated soil that had left the commercially grown cousins on an adjacent plot shriveled brown husks. Eubanks had refused to coddle her hybrid plants, allowing them not a drizzle of irrigation. Instead, she had given them something far more valuable: a genetic heritage that enabled them to flourish amidst the drought.

"It was truly amazing, because at the end of the summer when I went in to harvest, there were no ears on the regular corn, and all of the ears on my plants were completely filled out," she recalls. "They were as beautiful as the ears of the fancy inbred lines that you see when you go to the seed trade association shows."

Eubanks, an adjunct professor of biology, had developed her remarkably drought- and pest-resistant hybrids by crossing two wild grasses related to corn. But, despite the demonstrated vitality of the plants, she was met with vociferous criticism from other scientists. They denounced her scientific articles on the origin and evolution of corn, leading some of the most prestigious scientific journals to refuse to publish her findings. Some scientists said they doubted the existence of her hybrids. She had literally suffered for her science, enduring years of personal attacks on her findings and her competence.

The scientific heresy that Eubanks espoused is that modern corn, Zea mays, did not evolve solely from a Central American grass known as teosinte, as was commonly thought. Rather, she contended, her experiments demonstrated that corn could have arisen from a serendipitously viable cross between teosinte and another corn relative, gamagrass or Tripsacum. Such crosses, argued the critics, could not possibly be fertile, just as the cross between a horse and a donkey--a mule--is always sterile. (None of the critics contacted by Duke Magazine would speak on the record.)

While fighting over the origin of corn in the murky millennia of the past might seem but an esoteric academic controversy, understanding that genetic origin has profound practical implications. Given the world's critical dependence on corn, resurrecting its genetic past could lead to a more secure agricultural future for the whole world. Mother Nature does not treat agriculture gently, continually conjuring pests and pestilences to attack existing strains. By drawing on antique genes, plant breeders can create resistant hybrids to battle these onslaughts.

For Eubanks, the success of 2002 marked a turning point. Throughout, she has proven as resilient as the plants she has bred, driven by the humanitarian dream that they could help feed people in famine-ridden countries and dramatically benefit U.S. agriculture. They could lower irrigation requirements, improve pest resistance, and reduce toxin contamination of a $30 billion-a-year harvest that supports vast livestock herds and yields industrial products ranging from clothing to ethanol. Now, her dream is moving steadily toward reality, with field trials of her corn hybrids proving their worth.

Eubanks is modest about her evolution into an accomplished genetics researcher, a process that involved several detours and yielded tales of serendipity populated by corn-decorated pottery, bronze door knockers, and chance encounters. But as Pasteur would have countered, "In the field of observation, chance favors only the prepared mind"; and, despite her self-effacement, Eubanks does exemplify the power of a prepared mind.

Her preparation began not in hard science but in anthropology, in the early 1960s, when she was a graduate student at the University of North Carolina at Chapel Hill. The subject of her work, the origins of American agriculture, was inspired by a memorable lecture. "I really stumbled into it," she says. "I was working on my master's in anthropology, and one day my professor in Mesoamerican archaeology gave a lecture on Zapotec urns from the valley of Oaxaca in southern Mexico." The urns featured bas-relief images of corn created by molding actual ears of corn.

"The way he crafted the whole lecture was as a mystery" about the origins and significance of these urns as historical artifacts, says Eubanks. "And I loved plants, and I loved art and archaeology, because I really wanted to be a classical archaeologist, originally. And that's because the only woman professor I had as a college undergraduate was a classical archeologist. She was the one role model in my whole college career that I had that I could say, 'Oh, a woman can do this.'"

Examples of Eubanks' gamagrass-teosinte crosses, which closely resemble the oldest corn in the archaeological record

Examples of Eubanks' gamagrass-teosinte crosses, which closely resemble the oldest corn in the archaeological record. Les Todd

Intrigued by the idea that images of the corn on the ancient Zapotec urns could constitute visions of past agriculture, she tracked down Paul Mangelsdorf, a botanist who had retired from Harvard University and was teaching part time at the University of North Carolina at Chapel Hill. Mangelsdorf, she had learned, was involved in a botanical archaeology project in Mexico. "When I walked in and told him what I was interested in, he said, 'You're just the student I have been looking for for years and could never find at Harvard.' "

Mangelsdorf was interested in exploring the corn images on the Zapotec urns as a possible archaeological treasure trove for understanding the origins of corn. Eubanks traveled to Oaxaca to study the urns as botanical artifacts--an effort that meant she had to learn botany, as well. "So, very early I was getting into interdisciplinary research between two widely divergent fields--the natural sciences and the social sciences," she says. "And it was difficult managing my dissertation committee, because members literally didn't understand how to talk to each other."

Following this initial exploration, Eubanks says that her study of the origins of corn "went dormant," although she continued to publish and teach on archaeological and anthropological subjects. Then she was reunited with Mangelsdorf, oddly enough, by way of a door knocker. Earlier, as she was finishing her Ph.D., Eubanks had come across a handsome, bronze door knocker decorated with cast ears of corn. She bought one for herself and gave one to her mentor.

Years later, when Mangelsdorf moved out of his house and into an apartment in Chapel Hill, he had to leave the door knocker behind. Missing his trademark decoration, he contacted Eubanks to ask where he could find another. "I didn't know where to get them, so I just took the door knocker off my door and mailed it to him," she says. "He was pretty flabbergasted, I guess, and we reconnected. When I visited him, I got interested in a new hypothesis he was testing in the laboratory--that modern corn originated from a cross between a primitive corn and a rare perennial teosinte that had just been discovered in Mexico." Eubanks readily learned the necessary laboratory techniques and began to explore the details of the chromosomes of the rare plant.

She found that when she crossed the teosinte with corn, the number and position of characteristic "knobs" on the chromosomes of the resulting plants did not square with the theory that corn had arisen from teosinte. "We were seeing amplification and transposition of chromosome knobs that were definitely against dogma and very exciting and interesting," she says.

At this point, Eubanks, who was going through a divorce and had small children, was fruitlessly applying for tenure-track jobs in anthropology. "It was 1984, and although I got on the short list of all the best jobs, a woman was not hired for any of the job openings in anthropology that year," she says. When Mangelsdorf recommended her to corn cytogeneticist Marcus Rhodes for a postdoctoral fellowship at Indiana University, she jumped at the chance. There, as she studied in more detail the chromosomes of teosinte-corn crosses, she encountered another "accident." In the experiment station where she worked, a former student had left a collection of gamagrass plants, Tripsacum. Eubanks began to examine the chromosomes of this grass under her microscope. "It was very clear to me that the architecture of the perennial teosinte chromosomes, which was quite different from the other Zeas, was very similar to Tripsacum."

That discovery launched Eubanks on an effort to produce hybrids by cross-pollinating teosinte and gamagrass. To the utter surprise and delight of Eubanks and her colleagues, the recombinant plants not only grew and flowered but also "produced little ears, and the little ears looked a lot like the oldest archeological ears." Further studies showed that when she crossed the teosinte-gamagrass recombinants with corn, the hybrids were both drought-resistant and resistant to rootworm, a major corn pest.

Eubanks says she believes that one key to the hybrids' hardiness is their root system, which is more extensive than that of modern corn strains. The roots of the plants she developed reach deeper into the soil to draw up moisture, she theorizes. In addition, the roots of her strains possess hollow chambers called "aerenchyma" that carry oxygen into even the most compacted soils. The aerenchyma also render the roots distinctly unfriendly to pests. "If you compare these roots to regular corn roots that do not have aerenchyma and are filled with lots of wonderful tissue for the bugs to feed on, you realize there is nothing in the roots of hybrid plants for the larvae to eat," says Eubanks. "They just don't get much nutrient when they feed on the roots. In fact, in our earliest experiments when we recovered larvae and weighed them, there were fewer, much smaller larvae coming off the recombinant corn plants by comparison with the extensive populations of healthy larvae that were twice as large coming off the corn control plants."

"Clearly, these plants are different," Eubanks says of her teosinte-gamagrass-recombinant strains. "They are perennial, so you don't have to grow them from seed. You just stick a cutting in the ground like a begonia, and it will root. And they can tolerate severe drought, acid soils, and even swamps. If, indeed, natural recombinants were involved in the domestication of corn, it could dramatically shift the paradigm of where and how corn originated." That "unshifted" paradigm holds that only teosinte was the ancestor of modern corn and not some oddball cross between teosinte and gamagrass.

Despite her successes, Eubanks' research continued to be called into question, with other researchers expressing doubts that her plants were true teosinte-Tripsacum crosses, even though she had solid DNA fingerprinting data proving the crosses.

"So, even in spite of all that, there were people, very important people, who were in complete denial," she recalls. "And they got up and said I didn't have hybrids. And I made my response, and I presented my evidence, and that's all I could do, because they were not ever going to accept it." Purdue plant geneticist Jules Janick found himself with a front-row seat at the controversy in 2001, when he sent out for scientific review an article by Eubanks for publication in the journal Plant Breeding Reviews, which he edited. "As I remember, there were three reviewers against her and two for her," says Janick. "After she answered all their questions, I decided to publish it." Janick notes that Eubanks at that time was "up against the world," calling her "gutsy" for her stand.

Another expert, Walton Galinat, a renowned professor emeritus in plant and soil sciences at the University of Massachusetts at Amherst, has been more outspoken on Eubanks' behalf. "She did something that nobody else was able to do--mainly get a hybrid between two of the relatives of corn, Tripsacum and teosinte," says Galinat. "And she is the only person that has knowingly gone ahead and done that." Says Galinat of Eubanks' detractors, "Partly it is a sexist thing, and they are kind of mad because they didn't do it. A lot of men are that way. They hate someone else that beats them to the draw. When it was pretty obvious she was going to win, they refused to acknowledge that."

Today, however, the steady flow of solid evidence has won much of the plant-science community to her side, and she has been publicly vindicated. She has been invited to speak at scientific symposiums, to contribute commentaries on scientific articles on maize origins, and to write a chapter on her hypothesis about corn's origins for a new book, Darwin's Harvest (Columbia University Press). She's even achieved some celebrity, having been featured in a new photography book, Faces of Science (W. W. Norton) along with luminaries such as Nobelists Francis Crick and Murray Gell-Mann and pioneering Harvard biologist E. O. Wilson.

Eubanks has now largely shifted her attention from studying corn's origins to realizing the potentially stunning agricultural benefits of her hybrid strains. She is planning a scientific expedition to Guatemala to search for natural hybrids, but that scientific study will be combined with a more practical objective. She will also seek to develop collaborations with local subsistence farmers to reintroduce genes from "ancient" strains into their crops to invigorate productivity and enhance drought and pest resistance in their crop strains.

Closer to home, Eubanks' company, Sun Dance Genetics, has formed numerous collaborations to field test her new hybrids. One set of field trials has already shown that the hybrids produce protein yields comparable with the best commercial hybrids. Other trials are exploring the hybrids' resistance to rootworm and the deadly mold aflatoxin and also whether the hybrids can be profitably grown in the drought-prone regions of North Carolina. Yet another trial now under way is examining how well the hybrids tolerate low levels of nitrogen--with the aim of reducing fertilizer requirements for corn.

"One major problem, amplified by Hurricane Katrina, is that nitrogen runoff from farmlands that drain into the Mississippi River Basin has created a large dead zone in the Gulf of Mexico," she says. "And most of the nitrogen runoff--the cause of the large algal blooms that deplete oxygen and kill aquatic organisms--comes from fertilizer applied to corn, which requires high levels of nitrogen to boost crop yields. So, if we can develop commercial corn hybrids that use far less nitrogen, it would be a huge benefit for this country and for the environment."

"The important thing is that all these traits came out of one breeding program," says Eubanks. "Even though I started by selecting for rootworm tolerance, we discovered some of the inbred lines were also resistant to drought and aflatoxin. So, you can develop hybrid corn that offers a complete package of traits in one plant, because the teosinte-gamagrass recombinants enable movement of suites of genes for different traits all at the same time with conventional plant breeding. It's unlike the biotechnology approach, where one transgene at a time is typically engineered into a plant."

Even when she is immersed in the arcana of genomics, Eubanks keeps her ... well ... roots deeply planted in the hard-pan realities of the farmers she seeks to help. She recalls with emotion when she presented her results to a group of some 600 Midwestern farmers. They told her they were at the mercy of large seed companies selling proprietary, genetically modified strains at high prices. "They cheered, gave me hugs, kisses, and told me incredible stories about the problems the takeover by genetically modified crop technology is causing the American farmer and small seed producers; and many had tears in their eyes," she recalls. "I was so inspired by those farmers, I will do my best to provide a product that will help save the American farm and move us toward more sustainable food-production methods that will benefit the environment." Looking back on her serendipitous journey from studying Mexican pottery to exploring the intricate depths of plant genes, she exclaims, "It was like it was meant to be. I tell you, I am really the accidental scientist!"