Free How to Build a Dinosaur by Jack Horner Page 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