The ligaments in the spine of a 20-ton diplodocus, seen here in an X-ray, had hardened into bone, fusing two vertebrae together. Rothschild's diagnosis: diffuse idiopathic skeletal hyperostosis—that is, arthritis.
It's easy to be misled by Rothschild's many highly focused observations and forget that his idea of the big picture is about as big as such pictures come. His latest research involves collecting data on the ankles of 50,000 modern birds in order to compare them with ankles he's observed in other animals dating back to Iguanodon, a Jurassic dinosaur. He is studying one of the most common complaints of his modern-era human patients—osteoarthritis—and projecting it far into the past.

"What Rothschild has done is greatly increase the confidence of the diagnosis," says Larry Martin, who has been dragooned by Rothschild into various collaborations. Some paleopathologists draw limited conclusions after studying a single bone; Rothschild channels his frantic energy toward compiling overwhelming evidence. "If you have too much ambiguity about what disease you're talking about," Martin says, "it's hard to be confident about your conclusions. Rothschild has expanded the entire scope of what paleopathology can do."

Rothschild's latest, massive bird experiment is one of his most ambitious efforts yet. "One of the challenges in humans is that osteoarthritis is the most common form of arthritis," he explains. Most physicians believe that excess weight—that is, contemporary obesity—has a lot to do with the outbreak of this problem. But after examining 10,000 dinosaur bones all over the world, Rothschild is not so sure.


"There are two known examples of osteoarthritis in dinosaurs, and that's in a herd of 39 found a mile under Brussels in a coal mine. That was an Iguanodon bernissartensis." The near-complete absence of the disease in dinosaurs makes it hard to argue that weight is a cause. So Rothschild is scouring the eons for other evidence. His dinosaurs have persuaded him to set aside the fashionable diagnosis of obesity. Modern birds, he thinks, may hold a more convincing clue.

Amid cramped towers of specimen cabinets, Rothschild moves with the antic pace of a silent-screen comedian. The long, shallow drawers slide open with a squeaky roar. At each one, he shuffles the boxes of specimens—some the size of shoeboxes, others no bigger than a pack of cards. He separates out the ones that fit his study. All the while he talks nonstop—not exactly to me, not exactly to the bones, but somehow to both.

He pops open a lid, and his forefinger fishes around until he finds the bird's anklebone. He touches the tiny joint ball. In many cases the bone is thinner than a straight pin, yet Rothschild can feel a bony spur no bigger than half a salt grain: the telltale sign of osteoarthritis. He mutters his findings (no spurs) and marks his sheet. His finger spends no more than two or three seconds in each box until . . . "Bingo!" He hands me an African bee eater captured by J. P. Chapin in the Belgian Congo on February 21, 1911. He invites me to feel the bird's osteoarthritis. It's hard to believe than he can really feel this tiny protuberance, yet there it is under a magnifying glass.

"I've gone through about 45,000 birds, so I'm pretty good at this," he says. Already he is flicking his way through a half dozen other boxes and soon finds another victim: a specimen of Coracias caudatus that died in the New York Zoological Society in 1932. It's like watching a Renaissance musician strike at the keys of an early clavichord. Before long I find myself coerced out of my job as a journalist and holding check sheets instead, taking Rothschild's commands as he confirms the data.

"Bruce isn't happy unless everyone is busy," Martin says. "I've often been handed busywork so I don't look unoccupied. I remember one trip, looking at him and realizing, 'Hey, you've got a full professor writing down your data for you.'"

What's good for the dinosaurs is also good for people. After journeying back in time to apply his knowledge of human bone disease to Jurassic animals, Rothschild returns to Ohio with dinosaur data that can benefit the living H. sapiens bones he heals during the workweek. With the lessons learned from dinosaurs, Rothschild refers fewer osteoarthritis patients to surgery and hopes to prove through his work that the proper treatment may instead be exercise therapy that rebuilds muscle control.

Dinosaurs, Rothschild notes, had joints whose movements were highly constricted; they could swing back and forth on a very narrow track. Human knee joints have much more rotational maneuverability. "The problem is that nature's design for humans didn't include exuberances of youth, like football and sports, that stretch out and damage ligaments; these don't repair, so muscles have to take over," he says. "As we get older and aren't as active, we slowly lose the muscles that sustain that stability." Because older ligaments are no longer strong enough to do that work, we contract osteoarthritis.

Sports, though, are just one contributing factor. There are many more, which is why Rothschild is turning to birds for help. "If you want to understand the disease, you want to take out the variables," he says. Birds are a helpful model; they are partway between people and dinosaurs in the design of their knees. By correlating osteoarthritis in living birds with their known behaviors, Rothschild hopes to learn more about the causal factors than he ever could from his human patients.

To a doctor whose arc of interest flits across the epochs, the differences between Iguanodon, the toothpicklike skeleton of a bird from the Belgian Congo, and that slouching teenager in the museum cafeteria are few but revealing. Nothing collapses the entire history of vertebrate evolution into a cozy family reunion quite like paleopathology.

"It's amazing when you look at a bird's ankle," Rothschild calls out while wiggling the frail joint of a flycatcher he's found in a specimen drawer. "Look how much it resembles a human knee."