The next day, elated as I supposed only an entomologist can be, I took a bus inland to a stop close to the edge of the nearby rain forest. I was accompanied by an assistant assigned to me by the Museum of Natural History in Colombo. His principal role was to assure local Jainists, whose religion forbids the killing of all animal life even down to the lowly ants, that I had been allowed a dispensation. Along a forest trail I soon found several more Aneuretus colonies. I studied them in the field, during intervals between occasional pounding downpours of rain. Several colonies I placed in artificial nests to study their communication, care of the young and mother queen, and other aspects of their social behavior. Back at Harvard, I worked with several colleagues to describe the aneuretine internal anatomy.
Almost thirty years later, as a Harvard professor, I directed an undergraduate student from Sri Lanka, Anula Jayasuriya, as she made further surveys of the aneuretines for her senior honors thesis. She found that the range of the species was shrinking, which was no surprise due to the relentless clearing of Sri Lanka’s lowland forest since the time of my visit. At this point I had Aneuretus simoni put on the list of endangered species compiled by the International Union for the Conservation of Nature, one of the few rare insect species well enough known even to be considered for this category.
During this period, the picture of the evolution of the small but world-dominant ants as a whole was coming into focus. More researchers were entering the study of fossil and living species. We were filling in the steps in evolution that led to surviving groups, while discovering previously unknown groups and the ancestral lines that linked them together.
For a while the largest gap of all remained, the ancestor of all the ants. There is no such thing as a living solitary ant. All living species, so far as we know, form colonies with a queen and her sterile (or almost sterile) daughters, who do all the work. Males are raised in the nest solely for the purpose of mating with virgin queens. They leave the nest to find mates, are not allowed to return, and soon die. King Solomon, who instructed, “Go to the ant, thou sluggard, consider her ways, and be wise,” was obviously not aware of all the facts of ant biology in his moral urging. Nonetheless, how did this bizarre but extremely successful social system come into existence? When I was a young scientist we had many fossils to study, some dating back to more than fifty million years before the present, but every species represented had worker castes. Of the origin of their social organization we knew nothing.
This grail we ant biologists sought was a link still missing—a primitive ant with colonies like those of the ancestral forms that lived more than fifty million years ago, and simple enough to provide clues to the origin of social behavior. The leading candidate of which we had knowledge at this time was the Australian dawn ant (Nothomyrmecia macrops). Unfortunately, like the living aneuretines of Sri Lanka, the species was known from only two specimens. These had been collected in 1931 in one of the most remote places in the world. The land was the relatively inaccessible sand-plain heath of Western Australia. In the 1950s this vast area, stretching from the small coastal town of Esperance in the west to the edge of the desertlike Nullarbor Plain in the east, and covering over ten thousand square miles in area, was entirely devoid of people. Two decades before my own visit, a party of adventurers had traveled on horseback through this heath from the transcontinental highway south to an abandoned homestead on the coast called the Thomas River Farm, thence about a hundred miles west to Esperance. The terrain they crossed is one of the biologically richest in the world. In the seemingly barren scrubland lived large numbers of plant species found nowhere else on Earth. The insects were mostly unknown to science.
With the group in 1931 was a young woman who had agreed to collect ants along the trail for John S. Clark, an entomologist at the Museum Victoria in Melbourne and the sole expert on ants in Australia at that time. The collector carried a jar of alcohol into which she dropped ants wherever she found them. When Clark examined the specimens he was startled to find two belonging to a previously unknown ant species, primitively wasplike in form. It appears to be closest in anatomy among all known living ants to what may have been the ancestor of all ants. Unfortunately, the collector kept no records during the trek of where particular ant species had been found. The Australian dawn ant might have been picked up anywhere along a hundred-mile line.
By the time I arrived in 1955 to study Australian ants, I was obsessed with the idea of rediscovering this enigmatic species. It was already a legend among naturalists. I wanted to know whether it was fully social, with well-organized colonies of queens and workers, or less so—perhaps just partway to the advanced condition of all other known ants. Biologists of the time otherwise had no idea of how advanced ant social life had originated, or why.
Still young at twenty-five and charged with energy and optimism, I invited two fellow enthusiasts to join me in the effort to rediscover Nothomyrmecia macrops. One was Vincent Serventy, a famous Australian naturalist and authority on the Western Australian environment. The other was Caryl Haskins, a longtime ant expert and at that time the newly appointed president of the Carnegie Institute of Washington. We rendezvoused in Esperance, loaded up on supplies, and headed east in an old army flatbed truck along a dirt track to the Thomas River Farm. The flat plain, clothed in flowering shrubs and herbaceous plants, was beautiful to behold and blessedly empty—we saw only one other vehicle during the entire trip. From this base we searched outward in all directions, night and day, for the better part of a week. Dingoes prowled around our camp at night, the summer sun dehydrated us, and our footsteps turned huge meat ant nests into boiling masses of angry red-and-brown, viciously biting defenders. Was I afraid? Never. I loved every minute of it.
We devoted one day of our search to a trip northward to Mount Ragged, a prominence on whose barren sandstone slopes the dawn ants might have been collected. The only water source, for the 1931 party and ourselves, was a moist spot on the roof of a shaded ledge, from which enough water dripped to fill one cup each hour. No dawn ants were located there either.
Our overall effort yielded many new species of ants, but not a single specimen of the dawn ant. Because of my high expectations, the failure was one of the greatest disappointments of my scientific life.
Our failed expedition was nevertheless widely publicized in the Australian press, and it stimulated further searches in the sand-plain heath by entomologists. There was a widespread feeling among the local scientific cognoscenti that if this special insect was to be rediscovered and studied, it should be by Australians and not by Americans, of whom more than enough had already visited the continent.
One such attempt was led by my former student Robert W. Taylor, who had completed his Ph.D. at Harvard and at the time was a curator of entomology at the national insect collections in Canberra, the capital of Australia. Bob was desperate to make the discovery, to seize this grail for himself and for the honor of Australian entomology. On the way west to dawn ant country, the group camped in a forest of mallee, a kind of shrubby eucalyptus. The night was chilly, and there seemed to be no good reason to search for any insects at all. But Taylor walked out anyway with flashlight in hand, just in case something might be active. A few minutes later he came running back, shouting, “I got the bloody bastard! I got the bloody bastard!” As his words hint, now famous among entomologists, the dawn ant had indeed been found—and if not by an Australian, at least by a New Zealander.
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).
Thirteen
A CELEBRATION OF AUDACITY
SIX 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 th
e 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.”
Letters to a Young Scientist Page 8