Although life is a continuous process, fertilization… is a critical landmark because, under ordinary circumstances, a new genetically distinct human organism is formed when the chromosomes of the male and female pronuclei blend in the oocyte.
— Medical Textbook Ronan O’Rahilly and Fabiola Miller, Human Embryology and Teratology, 3rd edition. New York: Wiley-Liss, 2001. p. 8.
