"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.)
"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]
"Zygote. This cell, formed by the union of an ovum and a sperm (Gr. zygtos, yoked together), represents the beginning of a human being." [Moore, Keith L. and Persaud, T.V.N. Before We Are Born: Essentials of Embryology and Birth Defects. 4th edition. Philadelphia: W.B. Saunders Company, 1993, p. 1]
"Although human life is a continuous process, fertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed. ... The combination of 23 chromosomes present in each pronucleus results in 46 chromosomes in the zygote. Thus the diploid number is restored and the embryonic genome is formed. The embryo now exists as a genetic unity." (O'Rahilly, Ronan and M�ller, Fabiola. Human Embryology and Teratology, 2nd edition. New York: Wiley-Liss, 1996, pp. 8, 29).
"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, pages 17 and 23.)
"Fertilization is a sequence of events that begins with the contact of a sperm (spermatozoon) with a secondary oocyte (ovum) and ends with the fusion of their pronuclei (the haploid nuclei of the sperm and ovum) and the mingling of their chromosomes to form a new cell. This fertilized ovum, known as a zygote, is a large diploid cell that is the beginning, or primordium, of a human being." [Moore, Keith L. Essentials of Human Embryology. Toronto: B.C. Decker Inc, 1988, p.2]
"Embryo: An organism in the earliest stage of development; in a man, from the time of conception to the end of the second month in the uterus." (Dox, Ida G. et al. The Harper Collins Illustrated Medical Dictionary. New York: Harper Perennial, 1993, p. 146.
"every time a sperm cell and ovum unite, a new being is created which is alive and will continue to live unless its death is brought about by some specific condition." (E.L. Potter, M.D., and J.M. Craig, M.D. Pathology of the Fetus and the Infant (3rd Edition). Chicago: Year Book Medical Publishers, 1975, page vii.)
"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]
When does a person begin? I will try to give the most precise answer to that question actually available to science. Modern biology teaches us that ancestors are united to their progeny by a continuous material link, for it is from the fertilization of the female cell (the ovum) by the male cell (the spermatozoa) that a new member of the species will emerge. Life has a very, very long history but each individual has a very neat beginning:
the moment of its conception.
The material link is the molecular thread of DNA. In each reproductive cell, this ribbon, roughly one meter long, is cut into pieces (23 in our species). Each segment is carefully coiled and packaged (like a magnetic tape in a minicassette) so that under the microscope it appears like a little rod, a chromosome.
As soon as the 23 paternally derived chromosomes are united, through fertilization, to the 23 maternal ones, the full genetic information necessary and sufficient to express all the inborn qualities of the new individual is gathered. Exactly as the introduction of a minicassette inside a tape recorder will allow the restitution of the symphony, the new being begins to express himself as soon as he has been conceived.
Natural sciences and the sciences of law speak the same language. Of an individual enjoying a robust health - a biologist would say that he has a good constitution -of a society developing itself harmoniously to the benefit of all its members, a legislator would state that it has an equitable constitution.
Nature works the same way. The chromosomes are the tables of the law of life, and when they have been gathered in the new being (the voting process is the fertilization), they fully spell-out his personal constitution.
What is bewildering is the minuteness of the scripture. It is hard to believe, although beyond any possible doubt, that the whole genetic information necessary and sufficient to build our body and even our brain, the most powerful problem-solving device, even able to analyze the laws of the universe, could be epitomized so that its material substratum could fit neatly on the point of a needle!
...
In his lifecapsule, the amniotic bag, the early being is just as viable as an astronaut on the moon in his space-suit: refueling with vital fluids is required from the mother-ship. This nurture is indispensable for survival, but it does not "make" the baby, no more than the most sophisticated space shuttle can produce an astronaut. Such a comparison becomes even more cogent when the fetus moves.
Thanks to a refined sonar-like imagery, Dr. Ian Donald, from England, a year ago succeeded in producing a movie featuring the youngest star in the world, an 11-week-old baby dancing in utero (in the uterus). The baby plays, so to speak, on a trampoline! He bends his knees, pushes on the wall, soars up and falls down again. Because his body has the same buoyancy as the amniotic fluid, he does not feel gravity and performs his dance in a very slow, graceful, and elegant way, impossible in any other place on the Earth. Only astronauts in their gravity-free state can achieve such gentleness of motion. (By the way, for the first walk in space, technologists had to decide where to attach the tubes carrying the fluids. They finally chose the belt buckle of the suit, reinventing the umbilical cord.)
When I had the honor of testifying previously before the Senate, I took the liberty of referring to the universal fairy-tale of the man smaller than the thumb. At two months of age, the human being is less than one thumb's length from the head to the rump. He would fit at ease in a nutshell, but everything is there: hands, feet, head, organs, brain, all are in place. His heart has been beating for a month already. Looking closely, you would see the palm creases and a fortune teller would read the good adventure of that tiny person. With a good magnifier the fingerprints could be detected. Every document is available for a national identity card.
With the extreme sophistication of our technology, we have invaded his privacy. Special hydrophones reveal the most primitive music: a deep, profound, reassuring hammering at some 60-70 per minute (the maternal heart) and a rapid, high-pitched cadence at some 150-170 (the heart of the fetus). These, mixed, mimic those of the counterbass and of the maracas, which are the basic rhythms of any pop music.
We now know what he feels, we have listened to what he hears, smelled what he tastes and we have really seen him dancing full of grace and youth. Science has turned the fairytale of Tom Thumb into a true story, the one each of us has lived in the womb of his mother.
And to let you measure how precise the detection can be: if at the beginning, just after conception, days before implantation, a single cell was removed from the little berry-looking individual, we could cultivate that cell and examine its chromosomes. If a student, looking at it under the microscope, could not recognize the number, the shape and the banding pattern of these chromosomes, if he was not able to tell safely whether it comes from a chimpanzee being or from a human being, he would fail in his examination.
To accept the fact that, after fertilization has taken place, a new human has come into being is no longer a matter of taste or of opinion. The human nature of the human being from conception to old age is not a metaphysical contention. It is plain experimental evidence.
~ Dr Jerome Lejeune, geneticist and discoverer of the cause and means of treatment for Down's Syndrome
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