Dr. Englbrecht stands outside the American Museum of Natural History.

Claudia Englbrecht, a postdoctoral fellow at the American Museum of Natural History from 2000-2001, was born in Munich, Germany. As a girl, she wanted to become a medical doctor, like her father, but he counseled her against it. So when Claudia enrolled at the University of Munich, she decided to study biology, with a major in zoology and minors in biochemistry, human genetics, and ecology. In her research for her Master's thesis, Claudia used DNA sequencing to explore the evolution of small freshwater crustaceans.

The evolution of species is normally represented as a tree of forked lines, with new species branching out from older ones. Once separated, these branches do not connect again, because different species do not interbreed. But under a theory called reticulate evolution, interbreeding can occur between closely related species, which means the evolutionary tree can sometimes look like a web (reticulate comes from the Latin word for net).

To find evidence for reticulate evolution, one would have to look at a species' DNA, because animals exchange genes when they interbreed. Claudia focused on related species of the genus Daphnia, which were thought to have evolved by reticulation. She sequenced DNA samples from several individuals in each species to look for signs of past or present interbreeding. "Sequencing then was not like it is today," she remembers. "It was such a hassle, and it took so long." Though Claudia was working less than a decade ago, DNA sequencing technology was far less automated than it is today, and much more laborious.

Since her supervisor was not trained in molecular biology, Claudia had to figure out what she was doing as she went along. Ultimately she got what she needed: enough lab experience to continue her research after graduation.

After studying Daphnia for another year, Claudia entered a Ph.D. program. For her doctoral research, she continued to explore the process of evolution, particularly speciation, or how one species might evolve into two separate ones. The most common cause of speciation is that animals from a single species become separated geographically. Because they are no longer able to interbreed, they evolve along different paths. This is called allopatric evolution.

Claudia was interested in a less popular theory, called sympatric evolution. According to the sympatric theory, animals can go down different evolutionary paths without being geographically separated. For example, by developing different feeding habits, two distinct species of the same fish can evolve in a single lake. But it is hard to prove that this has happened after the fact. "The problem with speciation," Claudia explains, "is that you look at species when they are already present—the end product. It's hard to see the process." Fortunately, an animal's genetic history is recorded in its DNA.