David Hillis has spent many wet nights chasing frogs. Once, when he was camping in Queensland, Australia, it started to rain, and to hunt frogs without getting his clothes wet, he set out naked into the rainforest. Another time, he was in Mexico with a group of undergraduate biology students when a downpour at three in the morning forced them from the beach where they had camped; the eighteen-mile drive to the nearest town lasted until dawn because he kept stopping the van to jump out and examine the giant frogs making their way across the road. The first time he asked his wife for a date, when they were freshmen at Baylor University, he invited her to go out and listen to frogs. (Before that, he had invited her to come up to his room to listen to “Voices of the Night,” a record of frog calls. She refused.)
But frogs aren’t the half of it. Hillis, 41, an evolutionary biologist and the director of the School of Biological Sciences at the University of Texas at Austin, won a $295,000 MacArthur Fellowship grant last year; one thing he hopes to do with the money is travel to Madagascar to study crayfish. (The MacArthur “genius” grants recognize individuals of exceptional creativity and promise; past Texas winners include political activist Ernesto Cortes, writers Cormac McCarthy and Sandra Cisneros, poet Edward Hirsch, mathematician Karen Uhlenbeck, and the late disaster-relief expert Fred Cuny.) Every year, the MacArthur Foundation’s selection committee evaluates the recommendations of more than one hundred nominators from a range of disciplines and awards twenty to forty grants of $200,000 to $375,000, with no strings attached. For Hillis, the grant means freedom to pursue projects that might not receive backing from traditional sources, like the National Science Foundation. “Most grant agencies like to fund projects that are pretty much a sure thing,” he says. “But in the history of science, the things that have turned out to be the most fascinating are also the most risky.”
In fact, says Hillis, his entire career has been an example of how pursuing an obscure interest can yield unexpected rewards. He has been a key contributor to the field of phylogenetic analysis, which is concerned with figuring out how life-forms are connected on the evolutionary tree. “When I first started working on phylogeny, as a graduate student, most people considered it to be a very limited field that was only applied to a small area of biology, taxonomy, but I was interested in it, so I pursued it,” he says. “But it turns out that my work has lots and lots of different applications to many different areas.” Those applications range widely—from tracing the origins of human diseases to figuring out that whales are more like cows than was previously thought. Two years ago, phylogenetic analysis of HIV samples helped convict a Louisiana doctor of injecting his ex-girlfriend with the virus that causes AIDS.
With the help of the techniques that Hillis and others have developed, biologists of all stripes are mapping the course of evolution, using computers to draw the branching patterns that connect species or individual organisms to their common ancestors.
Though Hillis spends much of his time in the lab or on the computer—developing the theory and methods of phylogenetic analysis—he remains an eager field biologist. One Friday evening in March, I accompanied Hillis and a group of graduate students on a trip to Bastrop County to look for frogs. The early spring in Central Texas had been dry, not so good for frogging (which is best done on warm, wet nights), but they had decided to try anyway. As we left Austin it was warm, at least, and the bruise-colored sky, sliced periodically by lightning, seemed to promise rain. Sure enough, a couple of hours later we found ourselves sitting in his truck on a stretch of pastureland dotted with small ponds, listening to hail beat down on the windshield as we waited out the storm.
Hillis is like the kid who not only collects snakes but whose enthusiasm makes all the other kids want to collect snakes too. He is friendly, pensive, and attends closely to his surroundings, about which he is hugely knowledgeable. While waiting in the truck, he cheerfully ran down a list of half a dozen local frog calls. “So the Houston toad sounds like this, high-pitched”—Hillis, trilling his tongue, produced a Houston toad sound. “The chorus frog, Strecker’s chorus frog, is a single note”—he made a noise like wind whistling through a crack—“and the Hurter’s spadefoot sounds like someone throwing up. When a bunch of them are calling, it sounds like a whole fraternity throwing up”—Hillis made several retching sounds.
The rain ended abruptly, too soon to have soaked the ground; worse, it had brought with it a sharp, frog-discouraging drop in temperature. Circling one pond after another with flashlights and headlamps, Hillis and the students didn’t hear any calls and found only a few bullfrogs and leopard frogs. Still, they went after what animals they could: “Snake!” someone yelled at the sight of a small, dark head peeking out of the water, and Hillis, in long pants and high-top canvas sneakers, a headlamp strapped to his forehead, scrambled into the water to grab it. “Over here!” someone else called, and everyone ran through the thick mud to gather around the prize find of the evening: a large diamondback water snake coiled in the brown muck of the water’s edge, the pearly rear half of a catfish protruding from its wide-open mouth.
Trying to understand what Hillis does is a bit like following him through the mud as he seizes one animal after another: He tackles a wide range of problems. What ties them together is his passion for evolution itself. “To me,” he says, “it’s fascinating to think about the cotton fibers in my shirt, and myself, and if you went back a billion years ago, we have the same ancestors, the cotton