Dr. DeSalle takes a moment awayfrom his research in the American Museum of Natural History Molecular Lab.

In addition to their commitment to biodiversity and conservation, the Museum's biology researchers are also united by a common theoretical approach called cladistics. The Museum is considered the birthplace of American cladistics, a system of defining and organizing species by their shared derived traits. In the past, species were discovered and named without an objective, overarching system. But according to cladistics, each branch on the evolutionary tree is defined by a specific trait, or character, that is passed down to all the species in that branch.

Of course, there are different ways to identify these defining hereditary traits. Probably the most useful is an animal's morphology—its shape and structure. But molecular genetics has added a powerful new tool: tracing evolutionary traits through DNA. Neither method is foolproof, because animals can sometimes end up with shared traits without inheriting them from a common ancestor. For instance, two unrelated species can both develop wings (consider a butterfly and a bat), so if you selected wings as the shared trait that indicated a common ancestor, you could be misled. This type of shared trait is called "convergence."

Genetic patterns are susceptible to the problem of convergence, too. They are also full of meaningless data that Rob calls "noise." But while other scientists debate the relative merits of morphology versus molecular data, Rob believes that, "Instead of opposing morphology with molecules, we should be putting them together, and letting the two different kinds of data tell us what our patterns are."

An example of this approach is a series of studies Rob did with curator David Grimaldi, one of Rob's first collaborators at the Museum. "He's a morphologist, and a wonderful artist—draws his flies like no one else can draw flies," Rob says admiringly. The two examined the same species of Drosophila flies—Grimaldi studying their morphology, and Rob looking at their DNA—and obtained conflicting results. "In essence, it turns out that neither of us had enough data," Rob says. "And the combination of the two data sets actually gave us a much more reasonable hypothesis."

Most of the time, the molecules and morphology agree, but when they don't, Rob says, the results can be startling. "One of my students, John Gatesy, who's at the University of California, Irvine, now, has looked at the relationship between hippopotamuses and whales. We can show really clearly with molecular data that they are sister taxa, which means they are close relatives," Rob explains.

Needless to say, this was a big surprise. Few would guess that whales and hippos are related by looking at them—that is, by their morphology. But in this case, Rob says, "the sequence data are overwhelming the morphological data." So researchers must now consider how these creatures might have descended from a common ancestor, a question that most likely would never have arisen without having looked at their DNA.

"It's just a really great time to be in science," says Rob. "I bet you every scientist in every age thinks that, but this is truly a neat time. The capabilities for us to gather data for almost any question at the genetic level are there." Being a Museum curator allows him to explore as many of these questions as he wants, which makes it the perfect job for Rob.

In addition to the stimulating environment and wealth of potential collaborators, the Museum also gives Rob the opportunity to help design exhibition spaces, such as "The Genomic Revolution" and "Epidemic!". "The Genomic Revolution" explored the science and technology of genomics research as well as the ethical, social, and legal implications of this research. "Epidemic!" explored infectious disease. Rob also helps create magazines for children, books of essays, and content for the children's website, Ology—and of course, online science courses for teachers, such as this one. But his primary focus is on his research. As one of over 40 curators at the Museum, Rob works on exhibitions and educational programs, while he continues to explore the many unanswered questions that make his scientific career an endlessly rewarding and fascinating pursuit.

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