Professor Guex has published Retrograde Evolution During Major Extinction Crises (Springer, 2016), which forms the basis for the invertebrate examples used in this book. John S. Torday, PhD, is a Professor on the Faculty of the Evolutionary Medicine Program at UCLA. He received his Bachelor of Arts degree from Boston University (1968), a Master of Science degree from McGill University (1971), a Doctor of Philosophy degree from McGill University (1974), and did post-doctoral training in Reproductive Medicine at the University of Wisconsin-Madison (1974-76).  He was previously on the Faculties of Harvard Medical School (1976-91) and the University of Maryland Medical School (1991-98). He has authored more than 100 peer-reviewed articles and 5 monographs on the subject of cellular-molecular evolution. William B. Miller Jr. MD. attended the Honors Program in Medicine at NorthwesternUniversity, graduating with a B.S. In Medicine (1973) and a Doctor of Medicine (1975). He is a member of the medical honors society, Alpha Omega Alpha. Dr. Miller was a practicing physician for 35 years. During that period, he publishing a number of  academic medical articles. A series of observations about the patterns of infectious disease made based on active medical practice spurred an interest in genetics, evolutionary biology and the microbiome and  ultimately led to the publication of The Microcosm Within: Evolution and Extinction in the Hologenome (2013). More than two dozen peer-reviewed academic articles on evolution and the microbiome and several more books on those topics as co-author and co-editor have followed.