First of all, that is just biological ignorance since there are so many more steps that have to be successfully followed before it is ready to be born, but not even birth guarantees a new life since birth is complicated and risky.
“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.
“In that fraction of a second when the chromosomes form pairs, the sex of the new child will be determined, hereditary characteristics received from each parent will be set, and a new life will have begun.”
Kaluger, G., and Kaluger, M., Human Development: The Span of Life, page 28-29, The C.V. Mosby Co., St. Louis, 1974.
“It should always be remembered that many organs are still not completely developed by full-term and birth should be regarded only as an incident in the whole developmental process.”
F Beck Human Embryology, Blackwell Scientific Publications, 1985 page vi
“It is the penetration of the ovum by a sperm and the resulting mingling of nuclear material each brings to the union that constitutes the initiation of the life of a new individual.”
Clark Edward and Corliss Patten’s Human Embryology, McGraw – Hill Inc., 30
“Although it is customary to divide human development into prenatal and postnatal periods, it is important to realize that birth is merely a dramatic event during development resulting in a change in environment.”
The Developing Human: Clinically Oriented Embryology fifth edition, Moore and Persaud, 1993, Saunders Company, page 1
“The zygote and early embryo are living human organisms.”
Keith L. Moore & T.V.N. Persaud Before We Are Born – Essentials of Embryology and Birth Defects (W.B. Saunders Company, 1998. Fifth edition.) Page 500
“The term conception refers to the union of the male and female pronuclear elements of procreation from which a new living being develops. It is synonymous with the terms fecundation, impregnation, and fertilization … The zygote thus formed represents the beginning of a new life.”
J.P. Greenhill and E.A. Freidman.
Biological Principles and Modern Practice of Obstetrics. Philadelphia: W.B. Saunders Publishers. 1974 Pages 17 and 23.
“[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.
“[All] organisms, however large and complex they might be as full grown, begin life as a single cell. This is true for the human being, for instance, who begins life as a fertilized ovum.”
Dr. Morris Krieger “The Human Reproductive System” p 88 (1969) Sterling Pub. Co
“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.”
James Bopp, ed., Human Life and Health Care Ethics, vol. 2 (Frederick, MD: University Publications of America, 1985)
“The formation, maturation and meeting of a male and female sex cell are all preliminary to their actual union into a combined cell, or zygote, which definitely marks the beginning of a new individual. The penetration of the ovum by the spermatozoon, and the coming together and pooling of their respective nuclei, constitutes the process of fertilization.”
Leslie Brainerd Arey, “Developmental Anatomy” seventh edition space (Philadelphia: Saunders, 1974), 55
“The zygote therefore contains a new arrangement of genes on the chromosomes never before duplicated in any other individual. The offspring destined to develop from the fertilized ovum will have a genetic constitution different from anyone else in the world.”
DeCoursey, R.M., The Human Organism, 4th edition McGraw Hill Inc., Toronto, 1974. page 584
“The science of the development of the individual before birth is called embryology. It is the story of miracles, describing the means by which a single microscopic cell is transformed into a complex human being. Genetically the zygote is complete. It represents a new single celled individual.”
Thibodeau, G.A., and Anthony, C.P., Structure and Function of the Body, 8th edition, St. Louis: Times Mirror/Mosby College Publishers, St. Louis, 1988. pages 409-419
“Each human begins life as a combination of two cells, a female ovum and a much smaller male sperm. This tiny unit, no bigger than a period on this page, contains all the information needed to enable it to grow into the complex …structure of the human body. The mother has only to provide nutrition and protection.”
Clark, J. ed., The Nervous System: Circuits of Communication in the Human Body, Torstar Books Inc., Toronto, 1985, page 99
“A zygote (a single fertilized egg cell) represents the onset of pregnancy and the genesis of new life.”
Turner, J.S., and Helms, D.B., Lifespan Developmental, 2nd ed., CBS College Publishing (Holt, Rhinehart, Winston), 1983, page 53
“Almost all higher animals start their lives from a single cell, the fertilized ovum (zygote)… The time of fertilization represents the starting point in the life history, or ontogeny, of the individual.”
Carlson, Bruce M. Patten’s Foundations of Embryology. 6th edition. New York: McGraw-Hill, 1996, p. 3
“Embryo: The developing individual between the union of the germ cells and the completion of the organs which characterize its body when it becomes a separate organism…. At the moment the sperm cell of the human male meets the ovum of the female and the union results in a fertilized ovum (zygote), a new life has begun…. The term embryo covers the several stages of early development from conception to the ninth or tenth week of life.”
Considine, Douglas (ed.). Van Nostrand’s Scientific Encyclopedia. 5th edition. New York: Van Nostrand Reinhold Company, 1976, p. 943
“In that fraction of a second when the chromosomes form pairs, [at conception] the sex of the new child will be determined, hereditary characteristics received from each parent will be set, and a new life will have begun.”
Kaluger, G., and Kaluger, M., Human Development: The Span of Life, page 28-29, The C.V. Mosby Co., St. Louis, 1974
“The development of a human being begins with fertilization, a process by which two highly specialized cells, the spermatozoon from the male and the oocyte from the female, unite to give rise to a new organism, the zygote.”
Langman, Jan. Medical Embryology. 3rd edition. Baltimore: Williams and Wilkins, 1975, p. 3
“It is the penetration of the ovum by a spermatozoan and resultant mingling of the nuclear material each brings to the union that constitutes the culmination of the process of fertilization and marks the initiation of the life of a new individual.”
Human Embryology, 3rd ed. Bradley M. Patten, (New York: McGraw Hill, 1968), 43.
“In this text, we begin our description of the developing human with the formation and differentiation of the male and female sex cells or gametes, which will unite at fertilization to initiate the embryonic development of a new individual. … Fertilization takes place in the oviduct … resulting in the formation of a zygote containing a single diploid nucleus. Embryonic development is considered to begin at this point… This moment of zygote formation may be taken as the beginning or zero time point of embryonic development.”
Essentials of Human Embryology, William J. Larsen, (New York: Churchill Livingstone, 1998), 1-17.
“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..”
From Human Embryology & Teratology, Ronan R. O’Rahilly, Fabiola Muller, (New York: Wiley-Liss, 1996), 5-55.
“[The Zygote] results from the union of an oocyte and a sperm. A zygote is the beginning of a new human being. Human development begins at fertilization, the process during which a male gamete or sperm … unites with a female gamete or oocyte … to form a single cell called a zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual.”
The Developing Human: Clinically Oriented Embryology, 6th ed. Keith L. Moore, Ph.D. & T.V.N. Persaud, Md., (Philadelphia: W.B. Saunders Company, 1998), 2-18:
