“The zygote is human life….there is one fact that no one can deny; Human beings begin at conception.”
Landrum B. Shettles, M.D., P.h.D. the first scientist to succeed at in vitro fertilization
“Human life begins at fertilization, the process during which a male gamete or sperm (spermatozoo developmentn) unites with a female gamete or oocyte (ovum) to form a single cell called a zygote. This highly specialized, totipotent cell marked the beginning of each of us as a unique individual.” “A zygote is the beginning of a new human being (i.e., an embryo).”
Keith L. Moore, The Developing Human: Clinically Oriented Embryology, 7th edition. Philadelphia, PA: Saunders, 2003. pp. 16, 2.
“Fertilization is the process by which male and female haploid gametes (sperm and egg) unite to produce a genetically distinct individual.”
Signorelli et al., Kinases, phosphatases and proteases during sperm capacitation, CELL TISSUE RES. 349(3):765 (Mar. 20, 2012)
“[The zygote], formed by the union of an oocyte and a sperm, is the beginning of a new human being.”
Keith L. Moore, Before We Are Born: Essentials of Embryology, 7th edition. Philadelphia, PA: Saunders, 2008. p. 2.
“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.”
Ronan O’Rahilly and Fabiola Miller, Human Embryology and Teratology, 3rd edition. New York: Wiley-Liss, 2001. p. 8.
“The first cell of a new and unique human life begins existence at the moment of conception (fertilization) when one living sperm from the father joins with one living ovum from the mother. It is in this manner that human life passes from one generation to another. Given the appropriate environment and genetic composition, the single cell subsequently gives rise to trillions of specialized and integrated cells that compose the structures and functions of each individual human body. Every human being alive today and, as far as is known scientifically, every human being that ever existed, began his or her unique existence in this manner, i.e., as one cell. If this first cell or any subsequent configuration of cells perishes, the individual dies, ceasing to exist in matter as a living being. There are no known exceptions to this rule in the field of human biology.”
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James Bopp, ed., Human Life and Health Care Ethics, vol. 2 (Frederick, MD: University Publications of America, 1985)