Dr. Allen Collins is curator for medusae and glass sponges in the Department of Invertebrate Zoology at the Smithsonian's National Museum of Natural History. He is also a zoologist with the National Marine Fisheries Service of the National Oceanic and Atmospheric Administration. Several scientists from the Fisheries Service work in the Museum in a cooperative arrangement. Allen's research focuses on the evolutionary history of relatively simple animals, cnidarians (such as jellyfishes and corals), sponges, and a little-known phylum called Placozoa. He generates and uses evolutionary trees, known as phylogenetic hypotheses, to better understand how the amazing biodiversity of these groups – in terms of morphology, life history, and genetics – has come to be. He took a roundabout route to becoming a zoologist. As a senior in high school, Allen actually dropped out of a marine biology course because it seemed hard. After majoring in mathematics and economics at Amherst College, he worked as a research economist for five years in New York and San Francisco. During that last year, he took a night class on "The History of the Earth" and just happened to become an avid hiker and tide pool visitor in the San Francisco Bay area. That class captured his imagination, opening his eyes to big questions about the history of life on Earth. After taking some undergraduate biology courses at the University of California, Berkeley, he started graduate school there at age 27, eventually earning his Ph.D. At first, Allen planned to study marine reptiles, but as he learned more about the Cambrian Explosion – when most major animal phyla first appeared about 540 million years ago – and early animal evolution, he developed a keener interest in the lineages of animals that diverged first: sponges, ctenophores, placozoans, and especially cnidarians.