Of course we still excavate bones, and we need to. But we also need to look deep into the bones, into their chemistry. A first step is to narrow and deepen our vision, looking at microscopic evidence like the internal structure of bone, and moving even deeper to seek fossil molecules. Mary is a pioneer in this research, and as an inveterate digger myself, I like to think of her work in a similar framework. She is digging, too, but for her the fossil bone is the equivalent of the siltstone of the Hell Creek Formation, and the fossils she is trying to extract are not femurs and skulls but tissues, cells, and molecules, starting with protein and perhaps, one day, even moving on to DNA.
Mary had been working on the edge of this frontier of paleontological research for a good ten years by the time she picked up the piece of B. rex femur and declared the dinosaur to be female and pregnant. The path she had taken to scientific research was not a straight line from college to graduate school. In 1989, when she first audited a class I was giving at Montana State, she had just finished a science education certification program. She was married, raising three children, and working as a substitute teacher.
“I finished my teaching certification in the middle of the year. I loved going to school and I saw that Jack was teaching a course and I told him, ‘I really want to sit in on your class.’ ”
So she signed up for a course on evolution. From her point of view the experience was mixed. “I ended up working incredibly hard, for no academic credit,” she says, “and I got a C, which I still don’t think was a fair grade. But it got me hooked. It really did. I realized that there was far more evidence for dinosaur-bird linkages, for evolution, for all these different things, than a layperson would begin to understand. And when I really got to looking at that, it sort of changed my way of thinking, my worldview.”
She had come to class as a young earth creationist, meaning that she believed the earth had been created some thousands of years ago. It was a view she held more or less by default. Many of her friends were young earth creationists, and although she was well versed in basic biology and other sciences, she had not studied evolutionary biology or given the subject a great deal of thought. “Like many hard-core young earth creationists,” she says, “I didn’t understand the evidence. When I realized the strength of the data, the evidence, I had to rethink things.”
Whenever people talk about the conflict between science and religion I think of Mary. She is a person of strong religious faith that she says has only gotten stronger as she has learned more about science. Her faith is personal, and it is not something she brings up in conversation, but when asked, she is open and clear about it. She says the strength of the evidence for the process of evolution and the several-billion-year-old age of the earth is a separate matter from moral values or belief in God. She came to the study of paleontology from a background in which the assumption was that “people study evolution trying to find a way around God and his laws.” Instead, she came to see science as a strictly defined process for gathering and evaluating evidence. “When I talk to Christian groups or when I teach in my class, I explain that ‘science is like football.’ There is a set of rules and everybody follows the same rules. The young earth creationists play basketball on the same field. It’s not pretty.” The essential question is whether a conclusion or hypothesis is supported by data or not. And that is separate, she says, from “things that I know to be true” in other realms, such as faith and morality.
Her approach fits well with the way I try to teach science, whether to graduate students or undergraduates who are majoring in art history. I don’t present a worldview or a set of answers, but a process, a method. A discussion about the age of the earth, for example, would not begin with the answers, but with the question of how we pursue an answer, and the simple set of rules that govern scientific research in pursuit of answers. No student in a class of mine has to believe anything I say, or anything that anyone else says. But if we are doing science, we have to deal with evidence.
After Mary finished that first course, she started working as a volunteer in our lab at the Museum of the Rockies. She became more and more interested in some of the work. “I had so many questions,” she says. After about a year and a half of preparing fossil material and peppering everyone in the lab with questions, it was clear that the level of her interest in dinosaurs and paleontology would never be satisfied by volunteering. Finally I said, “Mary, go to grad school. Figure it out for yourself. Stop bugging everybody about it.” And she did.
Within four years she had a Ph.D., even though she was working, teaching, and raising her children. And her dissertation was the first, but not the last, time she stirred up some dust in the stuffy attic of dinosaur science.
The subject of the research, indeed the field she chose to specialize in, was a matter of chance and necessity. She turned to the fine structure of bone because it was something she could do without leaving home and children for the two months or so a full field season would require. The choice was a good one. Within paleontology the study of ancient, fossilized bone at a microscopic level—paleohistology—was a field with a great deal of promise. The potential was there for discoveries of much greater significance than the discovery of a new
Triceratops
skeleton, or even a new species, which was what she might have expected in the field.
For most of the last century or so, as the great dinosaur skeletons were uncovered in the American West, China, and around the world, paleontology has been a collector’s game. The romance was in finding the new species and putting them on display for the public. Even now, a new discovery of the biggest or smallest or newest kind of dinosaur is sure to make the news.
This is not to denigrate collecting. It is the basis of the entire science of paleontology. It is how we find the past. And the collected fossils have been used in many, many ways, most importantly of all to track the course of evolution over millions of years. As we conduct vertical explorations into deep time, we find which dinosaurs came first and which later. We see how the characteristics of one kind of animal appear in later eras in descendants that branch out with new traits—what are called derived characteristics.
Thus, 160 million years of dinosaur evolution have been charted in the crest on a humerus, the tilt of a pelvis, the length of hind limbs, as well as the shape of skulls and teeth, the digits on a foot or hand, domed skulls, and weaponlike tails. They were measured and inspected, divided into Ornithischians and Saurischians and their subgroups. In the fall of 2006 Peter Dodson, a paleontologist at the University of Pennsylvania, and Steve Wang, a statistician at Swarthmore, counted 527 known genera of dinosaurs and calculated that this represented about 30 percent of the number of genera that actually lived. That’s nonavian dinosaurs.
Many of those genera, they suggested, would never be found because they weren’t preserved as fossils. The fossil record, after all, is a sampling of the kinds of creatures that lived in the past. Becoming a fossil is no small trick. The organism has to die in an environment where it is buried fairly quickly, and the burial must last. Sediment must enclose the fossil and be turned into rock by time and pressure. The rock has to survive geological processes that could transform it and destroy the fossils within. And if the fossil is to be found and studied, the slow action of the earth must bring the rock and its enclosed treasure to the surface, where the elements can unwrap the gift for someone like me to find before those same elements destroy the fossil.
Fossils have always been rare and precious. And only recently has it become a common practice to cut them up or smash them to bits for microscopic and chemical study. In the early 1980s I went to Paris to learn how to make thin, polished wafers of fossilized bone that would allow a microscopic investigation of the interior structure. I was not engineering a vacation for myself. I was not a gourmet with a yearning to sample the work of great French chefs. As for travel, I would have probably chosen some desolate, eroding, fossil-rich locale in Mongolia if I had my pick of destination. Then, as now, dinosaurs were my work, hobby, and obsession. I would have been happy to learn how to make and study thin sections if I had found someone closer to work with. But paleohistology was an exceedingly small field and Armand de Ricqlès, at the Sorbonne , was my best chance as a teacher and mentor.
INSIDE THE BONES
Paleohistology, essentially the study of ancient tissues, in my case the investigation of the microstructure of dinosaur bone, had picked up speed in the 1980s, when scientists came to see many dinosaurs as warm-blooded. One of the most crucial arguments involved structures called Haversian canals, small tunnels for blood vessels. Some dinosaur bone was riddled with them, meaning that it had the kind of rich blood source that characterizes fast-growing bone in birds and mammals. Cold-blooded reptiles grow differently, and their bone looks different. Dinosaurs were beginning to look much more like ostriches than alligators.
Other findings were also important in building the case that many dinosaurs were warm-blooded, unlike other reptilians. Population structures, such as the ratio of predators to prey, and parental behavior both suggested dinosaurs were more like ground-nesting birds than any living reptiles.
By the time Mary was doing her master’s work in the early nineties, we were using new techniques. CT scans of fossils showed us interior structure without doing damage to a fossil. Scanning electron microscopes let us see the smallest details. She was learning and using those techniques and more, and dinosaur paleontology had changed enough that her work did not need to take her to Paris. She collaborated with colleagues outside of paleontology in Montana and elsewhere. And of course, her techniques took advantage of the explosion in computing power that has changed all aspects of science profoundly. It is something of a shock to remember that in the early eighties, e-mail was unknown to most of us, personal computers were just beginning to become popular, and the World Wide Web was nowhere to be seen. We didn’t have cell phones in Paris. In the summers, doing fieldwork, we had no phones. We relied on the ancient technology of walkie-talkies.
For her dissertation Mary wanted to study load-bearing bones in some of the large two-legged dinosaurs. From work on a
T. rex
specimen found in 1990 she concluded that the tissue in load-bearing fossil bones would be different than that of bone that did not bear weight. She wanted to test her hypothesis. What led her to go in a different direction was a happy accident, although it didn’t exactly seem like that to her at first.
In order to study these bones, she was making thin cross-sections for study under a microscope. But bone, even modern bone, is not easy to work with. And fossilized bone, part rock, part preserved bone, part who knows what, was really difficult. So she was having some trouble getting the sections right.
“I had a friend in the vet lab, a bone histologist who was helping me with a problem I was having making thin sections.” The friend went to a veterinary conference to give a talk on her studies of bone histology in modern animals during the time she and Mary were working on dinosaur thin sections. Among the sections mounted on microscope slides that she took to project on a screen was one of the
T. rex
, Museum of the Rockies specimen 555, or MOR 555. During the question-and-answer session she was asked what the oldest bone was that she had worked with. Funny you should ask, she said, and showed the slide of the
T. rex
femur.
Then, after the session was over, someone in the audience came up to the podium and said, “Do you realize you’ve got red blood cells in that dinosaur bone? ”
The result, Mary said, was that Gail “called me up as soon as she got back. And she had me come over and look at it and I thought, There is no way in God’s green earth that anybody’s going to believe that these are blood cells.” But that’s what they looked like, and there they were, right in the Haversian canals where they ought to have been.
This was, in a certain sense, an inconvenient discovery, if indeed it was a discovery. Any claim for the discovery of fossil red blood cells that were sixty-plus million years old would be controversial. And Mary, whose ambition was to do a manageable chunk of research to get her master’s, would have to try to prove or disprove the discovery and then defend her findings in a very public way. She did not feel ready for this kind of attention. It was a bit like being called up from the minor leagues to pitch in Yankee Stadium when you weren’t sure you had control of your curveball yet.
She had a good, safe dissertation project ready to begin, solid work, but nothing that would suddenly push her into the limelight. The last thing she wanted, the last thing many graduate students would want, was to research a highly controversial claim for a dissertation. If an established scientist were to report remnants of red blood cells in dinosaur bones, that would be hard enough to defend. A dissertation that reported such an extraordinary find would inevitably draw some negative attention. Consequently, Mary held off on telling me about the apparent red blood cell remnants. She wanted to proceed slowly and carefully and to have all her ducks in a row before she approached me to discuss the apparent find. Another grad student who had seen the tissue sample told me what was going on, and I called Mary in to talk.
As Mary remembers it, I was furious. She felt she was being called on the carpet to explain this highly suspect “discovery.” Mary laid out quite clearly what evidence she had. She didn’t think she had any proof that these were red blood cells. But there was a lot of evidence that pointed in that direction. After a long conversation I suggested that she do her dissertation by setting up the hypothesis that these were fossilized red blood cells, and then try to knock it down.