Letters to a Young Scientist (11 page)
It turned out that the dawn ant is a winter species. The workers wait in their nests and come out on cool nights to forage for mostly insects, many of which are numbed and easy to catch. The species is part of the ancient Gondwanan fauna, insects and other creatures of which a large part originated in Mesozoic times during the early breakup of the Gondwanan supercontinent and the drift northward of New Zealand, New Caledonia, and Australia. The relict elements, of which the dawn ant is part, are species adapted to the south temperate zone, and sometimes to the cool-temperature regimes of winter. I should have anticipated that possibility when searching in midsummer out of Esperance. But I didn’t.
With a population of dawn ants located, a flood of studies followed, during which virtually every aspect of the biology and natural history of the species was explored. Dawn ants proved to be elementary in most aspects of their social behavior, but they are not the fundamentally less social creatures we had hoped to find. Like all other known ants, they form colonies with queens and workers. They build nests, forage for food, and raise their sisters. All are cooperating subordinate daughters of the mother queen.
To discover the origin of all the ants, even taking into account their diminutive stature, is as important as finding the origin of dinosaurs, birds, and even our own distant ancestors among the mammals. I realized that without a satisfactory living link, researchers needed to find the right fossils from the right geological period to make further progress. Until 1966, however, the earliest known fossils were between a relatively youthful fifty million and sixty million years old, by which time, in the early to middle Eocene Period, the ants were already abundant and highly diversified. They were also globally distributed. We had even found an extinct species of dawn ant similar to the living one of Australia, preserved in the Baltic amber of Europe.
It was all very frustrating. Ants obviously had arisen during the Mesozoic Era, which ended sixty-five million years ago. But for a long time we had not a single Mesozoic specimen. It seemed as though a dark curtain had been lowered over the ancestors and earliest species of these world-dominant insects. Then, in 1966, word came to Harvard that two specimens of what appeared to be ants had been found in ninety-million-year-old amber from a geological deposit in, of all places, not some exotic far-off fossil bed but smack on the shores of New Jersey, and they were on the way for me to examine. At last the curtain might lift! I was so excited that when I fished the amber piece out of the mailing package I fumbled and it dropped to the floor. It broke into two pieces that skittered away from each other. I was aghast. What disaster had I wrought? However, to my great relief each piece contained an entire separate ant, and neither of the fossils had been damaged. When I polished the surface of the pieces into glassy smoothness, I found the external form of the specimens to be preserved almost as though they had been set in resin only a few days earlier.
My collaborators and I named the Mesozoic ant
Sphecomyrma freyi
, the first generic name meaning “wasp ant,” and the second in honor of the retired couple who had found the specimens. The generic name was fully justified: the species had a head that was mostly wasplike, some parts of the body were mostly antlike, and other parts of the body were intermediate in form between wasps and ants. In short, the missing link had been discovered, another grail found.
The announcement of the discovery set off a flurry of new searches by entomologists for ants and antlike wasps in amber and sedimentary rock deposits of late Mesozoic age. Within two decades many more specimens turned up in deposits from New Jersey, Alberta, Burma, and Siberia. In addition to more
Sphecomyrma
, new species at other levels of evolutionary development came to light. The story of the early diversification of the ants began to unfold. We found that it reaches back at least 110 million years and probably well beyond, to as far as 150 million years before the present.
Yet, sadly, we still had only fossils. No living evolutionary links had been found whose social behavior could be studied in the field and laboratory. It appeared that direct knowledge of the early stages of social behavior in the ants might have to be pieced together indirectly. The Australian dawn ant and a small number of other comparably primitive lines among the living ants might prove the best that would ever be found.
Then in 2009 came a complete surprise with at least the potential to change the big picture. A young German entomologist, Christian Rabeling, was excavating soil and leaf litter in rain forest near Manaus, in the central Amazon. Rabeling, with whom I’ve since worked in the field, has the deserved reputation of leaving, literally, no stone unturned. He also readily climbed trees, unaided by equipment, to bring down ant colonies nesting in the canopy. One day, as he was picking up every new kind of ant he could find, he spotted a single pale, odd-looking specimen crawling beneath the fallen leaves. Picking it up, he realized that he could not place it to any known genus or species of ants.
During a visit to Harvard he brought his discovery along with the rest of his collection to the “Ant Room.” Here, in cramped quarters on the fourth floor of Harvard’s Museum of Comparative Zoology, is kept the largest and most nearly complete classified collection of ants in the world. Built up by a succession of entomologists over more than a century, it contains perhaps a million specimens (no one has volunteered to make an exact count), belonging to as many as six thousand species. Ant experts from around the world come to these quarters to identify specimens they have collected on their own, and to conduct research on classification and evolution. Several were present when Rabeling brought in his Amazonian oddity.
After much consternation, the group invited me in from my office across the hall. I remember the moment vividly. Taking a look under the microscope, I said, “Good God, this thing must be from Mars!” Which meant I didn’t have a clue either. Later, when Rabeling described the species formally in a technical journal, he gave his ant the name
Martialis heureka
, which means, roughly, “the little Martian that has been discovered.” It was an ant, all right, and proved an earlier branch in the ant family tree than even the Australian dawn ant. At this writing three years later, no further Martialis ants have been found. The Amazon is a very big place to look, however, and I expect a colony will eventually be located if the species is truly social, and perhaps by one or more of the growing group of young ant experts in Brazil.
You may think of my story of ants as only a narrow slice of science, of interest chiefly to the researchers focused on it. You would be quite right. But it is nonetheless at a different level from an equally impassioned devotion to, say, fly fishing, Civil War battlegrounds, or Roman coins. The findings of its lesser grails are a permanent addition to knowledge of the real world. They can be linked to other bodies of knowledge, and often the resulting networks of understanding lead to major advances in the overall epic of science.
The basic tree of life with gene exchanges during the earliest evolution, as envisioned by the microbiologist W. Ford Doolittle. Modified from the original drawing in “Phylogenetic classification and the universal tree,” by W. Ford Doolittle,
Science
284: 2124–2128 (1999).
S
IX YEARS BEFORE
the discovery of the archetypical ant
Martialis
in the Amazon forest, a major effort had begun by entomologists to work out the family tree, more technically called the branching phylogeny, of all the living ants. Therein lies yet another chapter of my story especially relevant to you. In 1997 I had finally retired from the Harvard faculty and stopped accepting new Ph.D. students. Nevertheless, in 2003, the chairman of the Graduate Committee of the Department of Organismic and Evolutionary Biology called one day and said to me, “Ed, we’ve already accepted our quota of new students for this year, but we’ve got one more, a young woman so unusual and promising that we’ll add her on if you’ll agree to be her de facto sponsor and supervisor. She’s a fanatic on ants, wants to study them above all else. And she has tattoos of ants on her body to prove it.”
Dedication like that I admire, and after looking at her record I saw that Harvard was ideal for her. And she, it seemed, would be ideal for Harvard. I recommended that Corrie Saux (later Corrie Saux Moreau) from New Orleans be forthrightly admitted. When she appeared I knew we had made the right decision. She breezed through the first-year basic requirements. By the end of the year she already had a clear idea of what she wished to do for her Ph.D. thesis. Three leading experts on ant classification, each in different research institutions, had just received a multimillion-dollar federal grant to construct a family tree of all the major groups of ants in the world, based on DNA sequencing—the ultimate technique for the job. It was an important but formidable undertaking that, if successful, would undergird studies on the classification, ecology, and other biological investigations of all of the world’s sixteen thousand known ant species. Also, understanding the ants, many of the specialists realized, means learning a great deal more about Earth’s terrestrial ecosystems.
Saux suggested that she write the three lead researchers for permission to decode one of the smaller taxonomic divisions of the ants (one out of the twenty-one in all). I said, yes, it would be an achievement worth a degree if she could manage it, and a good way to meet other experts and work with them.
Soon afterward, however, she came back to tell me that the project leaders had turned her down. They were disinclined to add a new, untested graduate student to the team. From my own student days, I had learned to have a tough skin, not to accept a no as a personal rejection. With that in mind, I said, “Okay, don’t let that get you down. What the project leaders decided isn’t a bad thing. Why don’t you pick something else that you’d like to do?”
A few days later she came back and said, “Professor Wilson, I’ve been thinking, and I believe I could do the whole project myself.” I said, “The whole project?” She responded with demure sincerity, “Yes, all twenty-one of the subfamilies, all the ants. I think I can do it.”
Corrie then added that the world-class collection at Harvard was a great advantage. All she needed, she said, was a postdoctoral assistant who had specialized in DNA sequencing. She knew one who was willing to take the job. Might I supply the money for his salary? After a pause, I said impulsively, more out of instinct than logical reflection, “Well, okay.”
There was no bravado in Corrie, no trace of overweening pride, no pretension. She was a quiet, serene enthusiast. As it turned out, she was also an open, helpful friend to fellow students and others around her. She’d come from New Orleans by way of San Francisco State University, and I took pride in her as a fellow southerner. I wanted her to succeed, and while I did not join as a collaborator, I found the funds to set up her laboratory. And why not? An effort like this celebrates imagination, hope, and audacity. And there was a fallback position for Corrie: if she fell short of the whole, she could use the part completed as a thesis. I even helped, a little, on the side. When I visited the Florida Keys on another project during the months that followed, I collected live ants of the genus
Xenomyrmex
for her, filling in a group difficult to obtain in the field. Along the way, she told me she needed to consult with an expert on some complex methods in statistical inference. I funded that also.
At this point I was determined to see Corrie Saux to the end. I felt that she could actually accomplish what she envisioned.
Her thesis was finished in 2007, read closely by her Ph.D. committee, and approved. On April 7, 2006, the core of her study was published as the cover article in
Science
, an achievement that would be considered exceptional even for a senior researcher. I admit I was nevertheless a bit tense when Corrie’s thesis went to the Harvard committee for review.
Then I learned that the three-person team with the larger grant had also finished their work and planned to publish the results later in the year, allowing history to record that the two studies had been conducted independently and simultaneously. Of this I warmly approved, especially since each of the three was a highly regarded scientist. But it also meant that Corrie Saux’s research was about to be thoroughly tested. What if the two phylogenies didn’t match? That was a scenario I didn’t want to think about.
To my great relief, however, the two phylogenies matched almost perfectly. There was a difference in the placement of one of the twenty-one subfamilies, the leptanilline ants, an obscure and little-known group. Even that variance in interpretation was later worked out through more data and statistical analysis.
The story of Corrie Saux Moreau’s ambitious undertaking is one I feel especially important to bring to you. It suggests that courage in science born of self-confidence (without arrogance!), a willingness to take a risk but with resilience, a lack of fear of authority, a set of mind that prepares you to take a new direction if thwarted, are of great value—win or lose. One of my favorite maxims is from Floyd Patterson, the light heavyweight boxer who defeated heavier men to win and for a while hold the heavyweight championship. “You try the impossible to achieve the unusual.”