Human Embryology & Teratology On When Life Begins

From Human Embryology & Teratology, Ronan R. O’Rahilly, Fabiola Muller, (New York: Wiley-Liss, 1996), 5-55.

“Fertilization is an important landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed… Fertilization is the procession of events that begins when a spermatozoon makes contact with a secondary oocyte or its investments… The zygote … is a unicellular embryo..”