Paging Doctor Darwin
By Reid R. Frazier
What do the kneecap of an early primate and the inner ear bone of one of the first mammals have to do with modern medicine? Pitt medical students are learning the surprising answers.
Bryan Ward wanted to know why a pea-sized chamber in the inner ear that is integral to a person’s balance also helps us listen to rock music. But his medical textbooks were no help. It wasn’t until the fourth-year medical student took a class last spring with a Carnegie Museum of Natural History paleontologist that the answer became clearer, courtesy of the tiny fossil bones of some of the world’s first mammals.
Ward is one of a growing cadre of University of Pittsburgh medical students who have already taken part in a unique effort by the school and the museum to teach future doctors why, when treating and diagnosing disease, evolution matters. Titled The Natural History of Medicine and led by an archaeologist, a mammalogist, and two paleontologists, the course is meant to underscore how the distant past can teach doctors-in-training important lessons about treating patients today.
“I had a question in my own research that I had no answer for until I took the course,” Ward says.
Through the elective offering, Ward met Zhe-Xi Luo, curator of vertebrate pale-ontology and associate director of research and collections at the Museum of Natural History. As luck would have it, Luo is world-renowned for his research on the inner ear of early mammals. Ward calls their meeting “a very happy coincidence.”
“I had no idea who was teaching the class before I enrolled,” he recalls. “I was incredibly surprised and excited to actually consult with an expert in the field—someone who could answer some of the evolutionary questions I had.”
Luo helped to critique Ward’s paper outlining the evolution of the saccule, a small chamber that helps with balance and senses very loud and very low sounds. It’s connected to parts of the brain that deal with emotion. In animals such as frogs, the saccules also help detect mating sounds. “Maybe that’s why people like rock concerts and sub-woofers,” Ward says.
“After Bryan handed in the first draft of his term paper, I realized we were working on the same problem,” says Luo, who studies how the inner ear of early mammals evolved to become more sensitive, an adaptation that helped them become, among other things, more active at night. Luo sees in the hearing capacity of the saccule a relic of the anatomy of the earliest mammals.
Learning the Scientific Method
“Essentially, we [museum scientists] are all anatomists,” says Luo. “We’re interested in anatomical changes shaped by evolution. That’s why the school of medicine was so interested in working with us.”
Anthropologist Sandra Olsen teamed up with UPMC and Pitt med students to perform a “digital dissection” of an Egyptian child mummy. Photo: Mindy McNaugher
But what can medical students really gain from working with scientists like Luo? It can make them better doctors, says John Mahoney, associate dean for medical education at Pitt’s School of Medicine.
“The way we understand medicine today has everything to do with evolution,” says Mahoney. “Avian flu didn’t just drop out of the sky. It was the result of some natural evolutionary process. Understanding the evolution of this pathogen really does help put the present day situation into perspective.”
Likewise, the evolution of human anatomy—from increased brain size to walking upright—has many medical implications, from sinus infections to knee and back injuries.
“There are bits and parts of human anatomy that are, frankly, annoying, but we have to live with them because that’s how we evolved,” says Chris Beard, the museum’s Mary R. Dawson Chair of vertebrate paleontology and one of the course instructors. “All organisms on the face of the earth evolve—we all have to play by the same rules. Understanding how virulent microbes evolve, for instance, can tell you a lot about understanding human disease.”
Now four years in the making, The Natural History of Medicine has grown to encompass two sections—on paleontology and archaeology. As part of their study, students get to visit the museum’s “Big Bone room” (where the museum stores much of its massive fossil collection), as well as the anthropology and mammal collections, and hear directly from some of the museum’s most eminent scientists, each internationally renowned in his or her own field of study. Above all, notes Mahoney, these future physicians get to see firsthand how these researchers explore the origins of human evolution.
“The scientists at Carnegie Museum are serious investigators,” Mahoney says. “They are terrific role models for students in learning how to develop a hypothesis, lay out a plan of investigation, and test out their hypothesis.”
The process a paleontologist uses to tease out clues about evolution from the fossil record is a lot like the steps a doctor will take to diagnose a patient complaining of abdominal pain or shortness of breath, says Maggie McDonald, associate vice chancellor for academic affairs, health sciences, at Pitt.
“Patients won’t just come to them with problems that have neat and tidy answers,” McDonald says. “Doctors need to understand how to gain and evaluate information using the scientific method to solve the problems their patients will present them with.”
The connection to the museum also gives students an experience that other medical schools can’t replicate, McDonald says. “By exposing them to these opportunities, the hope is that a few of them will get excited enough to use the museum as a resource for a project,” she notes. “It’s an experience students at other medical schools simply can’t get.”
Sandra Olsen, the museum’s curator of anthropology and course instructor, says it’s important for students to understand that the medical problems they face in today’s patients are rooted in humanity’s distant past.
“You can find parasites in Egyptian mummies,” says Olsen. “You can also find diseases like cancer, smallpox, and osteoporosis in ancient human remains.” Clay figurines and wall carvings from the ancient world depict ailments like dwarfism and elephantiasis; ancient papyrus tablets inscribed with hieroglyphics reveal the use of herbs and poultices to treat diseases.
Olsen’s own work in the early domestication of animals illustrates how rapidly diseases evolve to suit their environments. With the domestication of the horse, cow, and pig, for instance, the microbes that cause disease jumped over into human populations. “It helps if these students understand the origins of well known diseases, so they can get a perspective on how to cope with future ones,” she notes.
The museum-medical school partnership has already spawned several interesting collaborations among students, faculty, and museum scientists. Freddie Fu, the renowned University of Pittsburgh Medical Center (UPMC) orthopedic surgeon who specializes in Anterior Cruciate Ligament (ACL) surgery, is currently working with Beard, as well as scientists at the Cleveland Museum of Natural History and the Pittsburgh Zoo, to look at how the human knee evolved.
"Learning that the common cold may have come from domesticated horses, that’s not something most medical students get to learn."
-Tanya Lucio, third-year Pitt medical student
Chris Beard (far right) and John Wible show fossils to Pitt medical students.
“I’m interested in how evolution influences bone morphology,” says Fu. “By looking at a bone we can understand how the ligament works, how the knee has evolved, and how different species use the knee.”
Sheila Ingham, a post-doctoral fellow in Fu’s lab, has been performing CT scans on 50-million-year-old primate fossils from the museum’s collection. These are some of the world’s first primates, distant ancestors of modern Homo sapiens.
“We want to know how this anatomy evolved to better understand the function of the human knee,” says Ingham. “Knowing this will help us better treat a patient when something goes wrong.”
Beard, an expert on early primates, says the knee problems Fu faces every day are a direct result of the advent of bipedalism (walking upright on two feet) in humans. This adaptation gave our human ancestors a distinct advantage: they could see farther, and their hands were freed up to manipulate objects and carry things. But walking on two feet instead of four increased the stress on the knees and vertebrae, leading to knee injuries and backaches.
Having narrower hips and bigger heads also made for more difficult childbirth. A monkey’s typical labor lasts about 15 minutes, versus several hours for a human’s.
Students learn about other anatomical baggage we carry from evolution. The appendix was a necessary digestive organ for our ancestors, who needed an extra compartment for food to ferment. Modern humans don’t need the appendix, and doctors may have to remove it if it gets infected.
Ear infections, a common ailment in children, are another vestige of evolution. As the size of the human brain increased, less space remained inside the skull for other functions. As a result, humans are one of the only species to get ear infections, says John Wible, the museum’s curator of mammals.
Unraveling the Past
Students who’ve taken the natural history course say they’ve gained no less than an entirely new insight into the practice of medicine. “Learning that the common cold may have come from domesticated horses, that’s not something most medical students get to learn,” says Tanya Lucio, a third-year med student who took the course her first year. Lucio teamed up with Olsen to perform a “digital dissection” of an Egyptian child mummy from the museum’s collection. The mummy, discovered in 1911, dates to the Early Greek and Roman period, circa 323-250 BC. Museum scientists had x-rayed the mummy in 1986, concluding it was a child of indeterminate sex, estimated to be about 4-6 years old. At the time, they believed it suffered from macrocephaly,
or an enlarged head.
With Jeffrey Towers, a UPMC musculoskeletal radiologist, Olsen and Lucio performed a CT scan. The CT is a kind of three-dimensional x-ray that shows bone and soft tissue. Olsen, Lucio, and Annie Nagy, a doctoral student in anthropology at Pitt, determined the child was a boy, about 3 years old, and showed signs of hypothyroidism, an ongoing endemic condition in Egypt resulting from iodine deficiency.
Lucio is hoping to enter the results from the CT scan into a worldwide database on Egyptian mummies. Olsen notes that Egyptologists from around the world have contacted her about the project.
“This will really contribute to our understanding of disease in ancient Egypt and to child mortality as a whole,” Olsen says.
Disease among humans and humankind’s ancestors isn’t the only thing the Museum of Natural History’s collections are teaching Pitt’s med students. John Lazo, Pitt’s Allegheny Foundation professor of pharmacology, loves to show his students a slide of a 150-million-year-old tumor taken from the fossilized bone of a dinosaur from the Jurassic Period now on display inside the museum’s Dinosaurs in Their Time exhibit. “Students are conditioned to think we get tumors because we live in an industrialized climate. This really shows them that cancer’s been around a whole lot longer than that,” Lazo says.
Lazo, who’s also director of Pitt’s Drug Discovery Institute (and a museum board member), says evolution underpins every aspect of medicine. It’s also a great way to understand cancer. “A cancer cell evolves, it spreads out, it finds niches in the body,” Lazo says, much like species evolve and adapt to their surroundings.
Even more promising: connections between the two institutions are evolving, too. Wible sees possibilities for partnerships with Pitt students and faculty and museum scientists on a variety of projects. The way he sees it, collaborating with the museum is a no-brainer.
“It’s important to talk to scientists outside your own discipline,” Wible notes. “You come into it from a different background, and you come out of it with something your own
perspective may have never given you.”