Embryology and Science Denial

On the question of when the life of a new member of the human species comes to be, the scientific facts squarely support the position of HHS.

The HHS has recently—and rightly—described life as beginning at conception. Dr. Richard Paulson’s denial of this claim contradicts the standard scientific position, and his arguments against that claim are fallacious and inaccurate.


In an early draft of its next strategic plan, the Department of Health and Human Services has described its mission as “serving and protecting Americans at every stage of life, beginning at conception” [emphasis added]. In an op-ed in the Los Angeles Times, Dr. Richard Paulson—a professor of obstetrics and gynecology and an infertility specialist—vehemently objects to HHS’s affirmation that life begins at conception. Paulson claims that this affirmation is based on religion rather than science, and that HHS should remove it from the report, because the agency’s endorsement of a religious view of human life violates the constitutional separation of church and state.

We heartily agree with Paulson that the HHS should define human life on the basis of “science and data, not faith-based belief.” But on the question of when the life of a new member of the human species comes to be, the scientific facts squarely support the position of HHS, not of Dr. Paulson. How he can be unaware of the pertinent facts is befuddling.

The standard science texts as well as scholarly articles in the fields of embryology, developmental biology, and microbiology assert the very position that Paulson says is merely faith-based and unscientific.

The Science of Embryology

The following are typical examples—only three of the many, many we could cite. These are from standard texts by embryologists, developmental biologists, and microbiologists:

“Human life begins at fertilization, the process during which a male gamete or sperm 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.

“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 capacitationCell Tissue Research.

“Although life is a continuous process, fertilization (which, incidentally, is not a ‘moment’) 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” (emphasis added; Ronan O’Rahilly and Fabiola Mueller, Human Embryology and Teratology, 3rd edition.

Many other examples could be cited, some of which may be found here.

These authorities all agree because the underlying science is clear. At fertilization—or, more precisely, when the sperm (a male sex cell) fuses with the oocyte (a female sex cell, more commonly referred to as an egg)—each of them ceases to be, and a new entity, one that is both genetically and functionally distinct from either parent, is generated. This new entity, initially a single totipotent cell, then divides into two cells, then (asynchronously) three, then four, eight, and so on, enclosed all the while by a membrane inherited from the oocyte (the zona pellucida), which then dissolves during implantation, allowing for continued growth in the direction of maturity as a member of the species. Even prior to implantation, however, these cells and membrane function as parts of a whole that regularly and predictably develops into the more mature stages of a complex human body.

How do we know that the result of sperm-oocyte fusion is a new entity, rather than a continuation of the oocyte? We know that a new entity exists because, once the sperm penetrates the oocyte, a completely new trajectory of biological development commences. The biological activity of an oocyte is directed toward successful fertilization; the biological activity of sperm is directed toward penetration of an oocyte. The biological activity of the new entity that results when sperm and oocyte fuse, however, is directed toward nothing less than the development of a mature human organism, distinct from either parent. Further, this new entity’s activities are directed not by instructions from the mother’s body, as some people wrongly suppose, but by its own unique set of instructions, especially the blueprint for development contained in its unique genetic material. The mother’s body recognizes the zygote and then the embryo as an entity distinct from itself. In fact, the embryo must send out chemical signals to prevent the mother’s immune system from attacking it. The embryo also emits chemical signals that induce changes in the lining of the mother’s uterus to enable successful implantation.

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