Daniel L. Hartl is Higgins Professor of Biology in the Department of Organismic and Evolutionary Biology at Harvard University. His laboratory studies population genetics, genomics, and molecular evolution. He has been honored with the Samuel Weiner Outstanding Scholar Award and Medal, the Medal of the Stazione Zoologica Anton Dohrn, and is an elected member of the National Academy of Sciences and the American Academy of Arts and Sciences. He is also a Past President of the Genetics Society of America and the Society for Molecular Biology and Evolution. Hartl's Ph.D. was awarded by the University of Wisconsin, he did postdoctoral studies at the University of California in Berkeley, and he has been on the faculty of the University of Minnesota, Purdue University and Washington University Medical School in St. Louis. In addition to more than 300 scientific articles, Hartl has authored or coauthored 24 books.; Andrew G. Clark is Professor of Population Genetics in the Department of Molecular Biology and Genetics at Cornell University. Earning a Ph.D. in Population Genetics at Stanford University, he did postdoctoral work at Arizona State University and the University of Aarhus, Denmark, and a sabbatical at the University of California at Davis. Prior to joining the Cornell faculty in 2002, he was a professor in the Department of Biology at Pennsylvania State University. Dr. Clark's research focuses on the genetic basis of adaptive variation in natural populations, with emphasis on quantitative modeling of phenotypes as networks of interacting genes. He was elected Fellow of the American Association for the Advancement of Science in 1994, and serves on review panels for the NIH, NSF, and the Max Planck Society. He also served as President of the Society for Molecular Biology and Evolution, and is on the Advisory Council for the National Human Genome Research Institute.