When Does a Human Life Begin? PDF Print E-mail

By Wilbur R. Roese, M.D.

Suppose a group of people was asked to name the tenth President of the United States. Depending on the level and type of education of the members of the group, they might give many different answers. They might even disagree.

What would such disagreement show? Would it mean that no one knows who was the tenth President, that there is disagreement among historians and it is impossible to determine who was the tenth President? Of course not. It would show that some members of the group were mistaken as to who was the tenth President.

The 1992 General Assembly stated, "...we do not have substantial agreement on when human life begins...." Does this mean that no one knows when human life begins? Does it prove that scientists are unable to determine when human life begins and there are no right or wrong answers to the question?

Just as books on American History show who was the tenth President, scientific textbooks show when human life begins. I assembled fourteen citations on when human life begins from various textbooks on medical embryology (a branch of biology dealing with embryos and their development) from the Health Sciences Library, University of Maryland at Baltimore. Here are examples:

"A zygote is the beginning of a new human being." (1)

"At the moment of fertilization there has been determined not only the existence of this new human being, but also his individuality." (2)

"Human development begins at fertilization (conception) when an oocyte (ovum) from a woman is fertilized by a sperm (spermatozoon) from a man." (3)

"Production of a new human being starts with the union of a spermatozoon and an ovum to form a single cell ....[A] single microscopic cell is transformed into a complex human being." (4)

"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." (5)

These are not quotations from antiabortion literature; they come from scientific textbooks used around the world. None of the texts stated that human life begins at birth, the third trimester, viability, the eighth week, ovulation or any stage of development other than fertilization. Not a single text stated that when human life begins is unknown, disputed or even uncertain. The textbooks date from 1919 to 1994, indicating not only that this is not a new discovery, but it has been unchanged for at least three quarters of a century.

The textbooks show that experts on human development agree as to when human life begins. They all agree that the life of a new human being begins at fertilization with the production of a zygote.

When human life begins is a subject on which there seem to be many opinions, but there is only one fact. The lack of agreement among Presbyterians is, therefore, not because the scientists have not been able to determine when human life begins, but because some Presbyterians are mistaken.

Dr. Roese is a General Medical Officer in the United States Army, and resides in Baltimore, MD. This article was the basis for his testimony to the 1995 G.A. National and Urban Issues committee.


1. Keith L. Moore, The Developing Human: Clinically Oriented Embryology (Philadelphia, PA: W.B. Saunders Co., 1988), p. 13.
2. Margaret Shea Gilbert, Biography of the Unborn (Baltimore, MD: The William & Wilkins Co., 1939), p. 5.
3. Keith L. Moore, T.V.N. Persaud and Kohei Shiota, Color Atlas of Clinical Embryology (Philadelphia, PA: W.B. Saunders Co., 1994), p. 1.
4. Anthony and Thibodeau, Textbook of Anatomy & Physiology, p. 754.
5. Jan Langman, Medical Embryology: Human Development-Normal and Abnormal (Baltimore, MD: The Williams & Wilkins Co., 1977), p. 3. (Dr. Jan Langman, M.D., Ph.D. was Professor of Anatomy at the University of Virginia, Charlottesville at the time this 419 page text was published. This book has been translated into nine languages.)



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